Updated on 2024/07/18

写真a

 
KOBAYASHI, Kazuyoshi
 
Affiliation
Faculty of Science and Engineering, Waseda Research Institute for Science and Engineering
Job title
Researcher(Associate Professor)

Education Background

  • 1997.04
    -
    2002.03

    東京大学大学院   理学系研究科   物理学専攻  

  • 1993.04
    -
    1997.03

    The University of Tokyo  

Research Areas

  • Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
 

Papers

  • Direct Measurement of the Spectral Structure of Cosmic-Ray <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mtext>Electrons</mml:mtext><mml:mo>+</mml:mo><mml:mtext>Positrons</mml:mtext></mml:mrow></mml:math> in the TeV Region with CALET on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, G. A. de Nolfo, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Physical Review Letters   131 ( 19 )  2023.11

    DOI

  • Direct dark matter searches with the full data set of XMASS-I

    K. Abe, K. Hiraide, N. Kato, S. Moriyama, M. Nakahata, K. Sato, H. Sekiya, T. Suzuki, Y. Suzuki, A. Takeda, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. H. Kim, Y. Itow, K. Martens, A. Mason, M. Yamashita, K. Miuchi, Y. Takeuchi, K. B. Lee, M. K. Lee, Y. Fukuda, H. Ogawa, K. Ichimura, Y. Kishimoto, K. Nishijima, K. Fushimi, B. D. Xu, K. Kobayashi, S. Nakamura

    Physical Review D   108 ( 8 )  2023.10

    DOI

  • Direction-sensitive dark matter search with 3D-vector-type tracking in NEWAGE

    Takuya Shimada, Satoshi Higashino, Tomonori Ikeda, Kiseki Nakamura, Ryota Yakabe, Takashi Hashimoto, Hirohisa Ishiura, Takuma Nakamura, Miki Nakazawa, Ryo Kubota, Ayaka Nakayama, Hiroshi Ito, Koichi Ichimura, Ko Abe, Kazuyoshi Kobayashi, Toru Tanimori, Hidetoshi Kubo, Atsushi Takada, Hiroyuki Sekiya, Atsushi Takeda, Kentaro Miuchi

    Progress of Theoretical and Experimental Physics   2023 ( 10 )  2023.10  [Refereed]

     View Summary

    Abstract

    NEWAGE is a direction-sensitive dark matter search experiment with a 3D tracking detector based on a gaseous micro time projection chamber. A direction-sensitive dark matter search was carried out at Kamioka Observatory with a total live time of 318.0 days resulting in an exposure of 3.18 kg·days. A new gamma-ray rejection and a head–tail determination analysis were implemented for this work. No significant non-isotropic signal from the directional analysis was found and a 90% confidence level upper limit on a spin-dependent weakly interactive massive particle (WIMP)–proton cross section of 25.7 pb for a WIMP mass of 150 GeV/c2 was derived. This analysis marks the most stringent upper limit in the direction-sensitive dark matter searches.

    DOI

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  • Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, G. A. de Nolfo, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Physical Review Letters   130 ( 21 )  2023.05

    DOI

  • Direct Measurement of the Cosmic-Ray Helium Spectrum from 40 GeV to 250 TeV with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, G. A. de Nolfo, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Physical Review Letters   130 ( 17 )  2023.04

    DOI

  • Cosmic-ray Boron Flux Measured from 8.4 GeV/n to 3.8 TeV/n with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, G. A. de Nolfo, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Physical Review Letters   129 ( 25 )  2022.12  [Refereed]

     View Summary

    We present the measurement of the energy dependence of the boron flux in cosmic rays and its ratio to the carbon flux in an energy interval from 8.4 GeV/n to 3.8 TeV/n based on the data collected by the Calorimetric Electron Telescope (CALET) during ∼6.4 yr of operation on the International Space Station. An update of the energy spectrum of carbon is also presented with an increase in statistics over our previous measurement. The observed boron flux shows a spectral hardening at the same transition energy E0∼200 GeV/n of the C spectrum, though B and C fluxes have different energy dependences. The spectral index of the B spectrum is found to be γ=-3.047±0.024 in the interval 25<E<200 GeV/n. The B spectrum hardens by ΔγB=0.25±0.12, while the best fit value for the spectral variation of C is ΔγC=0.19±0.03. The B/C flux ratio is compatible with a hardening of 0.09±0.05, though a single power-law energy dependence cannot be ruled out given the current statistical uncertainties. A break in the B/C ratio energy dependence would support the recent AMS-02 observations that secondary cosmic rays exhibit a stronger hardening than primary ones. We also perform a fit to the B/C ratio with a leaky-box model of the cosmic-ray propagation in the Galaxy in order to probe a possible residual value λ0 of the mean escape path length λ at high energy. We find that our B/C data are compatible with a nonzero value of λ0, which can be interpreted as the column density of matter that cosmic rays cross within the acceleration region.

    DOI PubMed

  • Search for neutrinoless quadruple beta decay of 136Xe in XMASS-I

    K. Abe, K. Hiraide, K. Ichimura, N. Kato, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, K. Sato, H. Sekiya, T. Suzuki, A. Takeda, S. Tasaka, M. Yamashita, B.S. Yang, N.Y. Kim, Y.D. Kim, Y.H. Kim, R. Ishii, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, A. Mason, Y. Suzuki, K. Miuchi, Y. Takeuchi, K.B. Lee, M.K. Lee, Y. Fukuda, H. Ogawa, K. Nishijima, K. Fushimi, B.D. Xu, S. Nakamura

    Physics Letters B   833   137355 - 137355  2022.10

    DOI

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  • Observation of Spectral Structures in the Flux of Cosmic-Ray Protons from 50 GeV to 60 TeV with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Physical Review Letters   129 ( 10 )  2022.09

    DOI

  • CALET Search for Electromagnetic Counterparts of Gravitational Waves during the LIGO/Virgo O3 Run

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, N. Ospina, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    The Astrophysical Journal   933 ( 1 ) 85 - 85  2022.07  [Refereed]

     View Summary

    Abstract

    The CALorimetric Electron Telescope (CALET) on the International Space Station consists of a high-energy cosmic-ray CALorimeter (CAL) and a lower-energy CALET Gamma-ray Burst Monitor (CGBM). CAL is sensitive to electrons up to 20 TeV, cosmic-ray nuclei from Z = 1 through Z ∼ 40, and gamma rays over the range 1 GeV–10 TeV. CGBM observes gamma rays from 7 keV to 20 MeV. The combined CAL-CGBM instrument has conducted a search for gamma-ray bursts (GRBs) since 2015 October. We report here on the results of a search for X-ray/gamma-ray counterparts to gravitational-wave events reported during the LIGO/Virgo observing run O3. No events have been detected that pass all acceptance criteria. We describe the components, performance, and triggering algorithms of the CGBM—the two Hard X-ray Monitors consisting of LaBr3(Ce) scintillators sensitive to 7 keV–1 MeV gamma rays and a Soft Gamma-ray Monitor BGO scintillator sensitive to 40 keV–20 MeV—and the high-energy CAL consisting of a charge detection module, imaging calorimeter, and the fully active total absorption calorimeter. The analysis procedure is described and upper limits to the time-averaged fluxes are presented.

    DOI

    Scopus

    5
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  • CALET on the International Space Station: a precise measurement of the iron spectrum

    O. Adriani, Yosui Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, Caterina Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, N. Ospina, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, Francesco Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

    Proceedings of Science   398  2022.05

     View Summary

    The Calorimetric Electron Telescope (CALET) was launched on the International Space Station in 2015 and since then has collected a large sample of cosmic-ray charged particles over a wide energy. Thanks to a couple of layers of segmented plastic scintillators placed on top of the detector, the instrument is able to identify the charge of individual elements from proton to iron (and above). The imaging tungsten scintillating fiber calorimeter provides accurate particle tracking and the lead tungstate homogeneous calorimeter can measured the energy with a wide dynamic range. One of the CALET scientific objectives is to measure the energy spectra of cosmic rays to shed light on their acceleration and propagation in the Galaxy. By the observation in first five years, a precise measurement of the iron spectrum is now available in the range of kinetic energy per nucleon from 10 GeV/n to 2 TeV/n. The CALET's result with a description of the analysis and details on systematic uncertainties will be illustrated. Also, a comparison with previous experiments' results is given.

  • Direct Measurement of the Nickel Spectrum in Cosmic Rays in the Energy Range from 8.8 GeV/n to 240 GeV/n with CALET on the International Space Station

    O.Adriani, Y.Akaike, K.Asano, Y.Asaoka, E.Berti, G.Bigongiari, W.R.Binns, M.Bongi, P.Brogi, A.Bruno, J.H.Buckley, N.Cannady, G.Castellini, C.Checchia, M.L.Cherry, G.Collazuol, K.Ebisawa, A.W.Ficklin, H.Fuke, S.Gonzi, T.G.Guzik, T.Hams, K.Hibino, M.Ichimura, K.Ioka, W.Ishizaki, M.H.Israel, K.Kasahara, J.Kataoka, R.Kataoka, Y.Katayose, C.Kato, N.Kawanaka, Y.Kawakubo, K.Kobayashi, K.Kohri, H.S.Krawczynski, J.F.Krizmanic, P.Maestro, P.S.Marrocchesi, A.M.Messineo, J.W.Mitchell, S.Miyake, A.A.Moiseev, M.Mori, N.Mori, H.M.Motz, K.Munakata, S.Nakahira, J.Nishimura, G.A.deNolfo, S.Okuno, J.F.Ormes, N.Ospina, S.Ozawa, L.Pacini, P.Papini, B.F.Rauch, S.B.Ricciarini, K.Sakai, T.Sakamoto, M.Sasaki, Y.Shimizu, A.Shiomi, P.Spillantini, F.Stolzi, S.Sugita, A.Sulaj, M.Takita, T.Tamura, T.Terasawa, S.Torii, Y.Tsunesada, Y.Uchihori, E.Vannuccini, J.P.Wefel, K.Yamaoka, S.Yanagita, A.Yoshida, K.Yoshida, W.V.Zober

    Physical Review Letters   128 ( 13 )  2022.03  [Refereed]

     View Summary

    The relative abundance of cosmic ray nickel nuclei with respect to iron is by far larger than for all other transiron elements; therefore it provides a favorable opportunity for a low background measurement of its spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the cosmic ray source and to model the Galactic propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than ∼3 GeV/n are available at present in the literature, and they are affected by strong limitations in both energy reach and statistics. In this Letter, we present a measurement of the differential energy spectrum of nickel in the energy range from 8.8 to 240 GeV/n, carried out with unprecedented precision by the Calorimetric Electron Telescope (CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The particle's energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This Letter follows our previous measurement of the iron spectrum [1O. Adriani (CALET Collaboration), Phys. Rev. Lett. 126, 241101 (2021).PRLTAO0031-900710.1103/PhysRevLett.126.241101], and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from 20 to 240 GeV/n our present data are compatible within the errors with a single power law with spectral index -2.51±0.07.

    DOI PubMed

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  • Diffuse supernova neutrino background search at Super-Kamiokande

    K. Abe, C. Bronner, Y. Hayato, K. Hiraide, M. Ikeda, S. Imaizumi, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, M. Miura, S. Moriyama, Y. Nagao, M. Nakahata, S. Nakayama, T. Okada, K. Okamoto, A. Orii, G. Pronost, H. Sekiya, M. Shiozawa, Y. Sonoda, Y. Suzuki, A. Takeda, Y. Takemoto, A. Takenaka, H. Tanaka, S. Watanabe, T. Yano, S. Han, T. Kajita, K. Okumura, T. Tashiro, J. Xia, G. D. Megias, D. Bravo-Berguño, L. Labarga, Ll Marti, B. Zaldivar, B. W. Pointon, F. D.M. Blaszczyk, E. Kearns, J. L. Raaf, J. L. Stone, L. Wan, T. Wester, J. Bian, N. J. Griskevich, W. R. Kropp, S. Locke, S. Mine, M. B. Smy, H. W. Sobel, V. Takhistov, J. Hill, J. Y. Kim, I. T. Lim, R. G. Park, B. Bodur, K. Scholberg, C. W. Walter, S. Cao, L. Bernard, A. Coffani, O. Drapier, S. El Hedri, A. Giampaolo, M. Gonin, Th A. Mueller, P. Paganini, B. Quilain, T. Ishizuka, T. Nakamura, J. S. Jang, J. G. Learned, L. H.V. Anthony, D. Martin, M. Scott, A. A. Sztuc, Y. Uchida, V. Berardi, M. G. Catanesi, E. Radicioni, N. F. Calabria, L. N. Machado, G. De Rosa, G. Collazuol, F. Iacob, M. Lamoureux, M. Mattiazzi, N. Ospina, L. Ludovici, Y. Maekawa, Y. Nishimura, M. Friend, T. Hasegawa, T. Ishida, T. Kobayashi, M. Jakkapu, T. Matsubara

    Physical Review D   104 ( 12 )  2021.12

     View Summary

    We have conducted a new search for the diffuse supernova neutrino background (DSNB) flux at Super-Kamiokande (SK), with a 22.5×2970-kton·day exposure from its fourth operational phase IV. With the new analysis we improve on the existing background reduction techniques and systematic uncertainties and take advantage of an improved neutron tagging algorithm to lower the energy threshold compared to the previous phases of SK. This allows for setting the world's most stringent upper limit on the extraterrestrial ν¯e flux, for neutrino energies below 31.3 MeV. The SK-IV results are combined with the ones from the first three phases of SK to perform a joint analysis using 22.5×5823 kton·days of data. This analysis has the world's best sensitivity to the DSNB ν¯e flux, comparable to the predictions from various models. For neutrino energies larger than 17.3 MeV, the new combined 90% CL upper limits on the DSNB ν¯e flux lie around 2.7 cm-2·sec-1, strongly disfavoring the most optimistic predictions. Finally, potentialities of the gadolinium phase of SK and the future Hyper-Kamiokande experiment are discussed.

    DOI

  • Search for tens of MeV neutrinos associated with gamma-ray bursts in Super-Kamiokande

    A. Orii, K. Abe, C. Bronner, Y. Hayato, M. Ikeda, S. Imaizumi, H. Ito, J. Kameda, Y. Kataoka, Y. Kato, Y. Kishimoto, M. Miura, S. Moriyama, T. Mochizuki, Y. Nagao, M. Nakahata, Y. Nakajima, S. Nakayama, T. Okada, K. Okamoto, G. Pronost, H. Sekiya, M. Shiozawa, Y. Sonoda, Y. Suzuki, A. Takeda, Y. Takemoto, A. Takenaka, H. Tanaka, T. Yano, S. Han, T. Kajita, K. Okumura, T. Tashiro, R. Wang, J. Xia, G. D. Megias, D. Bravo-Berguño, L. Labarga, Ll Marti, B. Zaldivar, F. D.M. Blaszczyk, E. Kearns, J. L. Raaf, J. L. Stone, L. Wan, T. Wester, B. W. Pointon, J. Bian, N. J. Griskevich, W. R. Kropp, S. Locke, S. Mine, M. B. Smy, H. W. Sobel, V. Takhistov, P. Weatherly, K. S. Ganezer, J. Hill, J. Y. Kim, I. T. Lim, R. G. Park, B. Bodur, K. Scholberg, C. W. Walter, L. Bernard, A. Coffani, O. Drapier, S. El Hedri, A. Giampaolo, M. Gonin, Th A. Mueller, P. Paganini, B. Quilain, T. Ishizuka, T. Nakamura, J. S. Jang, J. G. Learned, S. Matsuno, L. H.V. Anthony, R. P. Litchfield, A. A. Sztuc, Y. Uchida, V. Berardi, M. G. Catanesi, E. Radicioni, N. F. Calabria, L. N. Machado, G. De Rosa, G. Collazuol, F. Iacob, M. Lamoureux, N. Ospina, L. Ludovici, Y. Nishimura, S. Cao, M. Friend, T. Hasegawa, T. Ishida, T. Kobayashi

    Progress of Theoretical and Experimental Physics   2021 ( 10 )  2021.10

     View Summary

    A search for neutrinos produced in coincidence with gamma-ray bursts (GRBs) was conducted with the Super-Kamiokande (SK) detector. Between December 2008 and March 2017, the Gamma-ray Coordinates Network recorded 2208 GRBs that occurred during normal SK operation. Several time windows around each GRB were used to search for coincident neutrino events. No statistically significant signal in excess of the estimated backgrounds was detected. The νe fluence in the range from 8 MeV to 100 MeV in positron total energy for νe+p → e++n was found to be less than 5.07 × 105 cm-2 per GRB at a 90% confidence level. For all GRBs, upper bounds were obtained on the fluence as a function of neutrino energy. Additionally, for GRBs at known distances, upper limits were set for the neutrino energy emission at the GRB.

    DOI

  • Search for neutrinos in coincidence with gravitational wave events from the LIGO–Virgo O3a observing run with the Super-Kamiokande detector

    K. Abe, C. Bronner, Y. Hayato, M. Ikeda, S. Imaizumi, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, M. Miura, S. Moriyama, Y. Nagao, M. Nakahata, S. Nakayama, T. Okada, K. Okamoto, A. Orii, G. Pronost, H. Sekiya, M. Shiozawa, Y. Sonoda, Y. Suzuki, A. Takeda, Y. Takemoto, A. Takenaka, H. Tanaka, S. Watanabe, T. Yano, S. Han, T. Kajita, K. Okumura, T. Tashiro, R. Wang, J. Xia, G. D. Megias, D. Bravo-Berguño, L. Labarga, Ll Marti, B. Zaldivar, B. W. Pointon, F. D.M. Blaszczyk, E. Kearns, J. L. Raaf, J. L. Stone, L. Wan, T. Wester, J. Bian, N. J. Griskevich, W. R. Kropp, S. Locke, S. Mine, M. B. Smy, H. W. Sobel, V. Takhistov, P. Weatherly, J. Hill, J. Y. Kim, I. T. Lim, R. G. Park, B. Bodur, K. Scholberg, C. W. Walter, L. Bernard, A. Coffani, O. Drapier, S. El Hedri, A. Giampaolo, M. Gonin, Th A. Mueller, P. Paganini, B. Quilain, T. Ishizuka, T. Nakamura, J. S. Jang, J. G. Learned, L. H.V. Anthony, D. G.R. Martin, A. A. Sztuc, Y. Uchida, V. Berardi, M. G. Catanesi, E. Radicioni, N. F. Calabria, L. N. Machado, G. de Rosa, G. Collazuol, F. Iacob, M. Lamoureux, N. Ospina, L. Ludovici, Y. Maekawa, Y. Nishimura, S. Cao, M. Friend, T. Hasegawa, T. Ishida, M. Jakkapu, T. Kobayashi, T. Matsubara, T. Nakadaira

    Astrophysical Journal   918 ( 2 )  2021.09

     View Summary

    The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO–Virgo Collaboration (LVC). Both low-energy (7–100 MeV) and high-energy (0.1–105 GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map; the most significant event (GW190602_175927) is associated with a post-trial p-value of 7.8% (1.4σ). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature.

    DOI

  • Direction-sensitive dark matter search with the low-background gaseous detector NEWAGE-0.3b”

    Tomonori Ikeda, Kiseki Nakamura, Takuya Shimada, Ryota Yakabe, Takashi Hashimoto, Hirohisa Ishiura, Takuma Nakamura, Hiroshi Ito, Koichi Ichimura, Ko Abe, Kazuyoshi Kobayashi, Toru Tanimori, Hidetoshi Kubo, Atsushi Takada, Hiroyuki Sekiya, Atsushi Takeda, Kentaro Miuchi

    Progress of Theoretical and Experimental Physics   2021 ( 6 )  2021.06

     View Summary

    <title>Abstract</title>
    NEWAGE is a direction-sensitive dark matter search using a low-pressure gaseous time projection chamber. A low alpha-ray emission rate micro pixel chamber had been developed in order to reduce background for dark matter search. We conducted the dark matter search at the Kamioka Observatory in 2018. The total live time was 107.6 d, corresponding to an exposure of 1.1 kg$\&amp;gt;$d. Two events remained in the energy region of 50–60 keV, which was consistent with the expected background of 2.5 events. A directional analysis was carried out and no significant forward–backward asymmetry derived from the WIMP-nucleus elastic scatterings was found. Thus a 90$\%$ confidence level upper limit on the spin-dependent WIMP-proton cross-section of 50 pb for a WIMP mass of 100 GeV$\&amp;gt;c^{-2}$ was derived. This limit is the most stringent yet obtained from direction-sensitive dark matter search experiments.

    DOI

    Scopus

    4
    Citation
    (Scopus)
  • Measurement of the Iron Spectrum in Cosmic Rays from 10GeV/n to 2.0TeV/n with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, J. Link, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, N. Ospina, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida

    Physical Review Letters   126 ( 24 )  2021.06

    DOI

  • Search for event bursts in XMASS-I associated with gravitational-wave events

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, H. Ogawa, K. Sato, H. Sekiya, T. Suzuki, A. Takeda, S. Tasaka, M. Yamashita, B.S. Yang, N.Y. Kim, Y.D. Kim, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, Y. Suzuki, B.D. Xu, K. Miuchi, N. Oka, Y. Takeuchi, Y.H. Kim, K.B. Lee, M.K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, K. Fushimi, G. Kanzaki, S. Nakamura

    Astroparticle Physics   129   102568 - 102568  2021.05

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • 222 Rn emanation measurements for the XENON1T experiment

    E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, V. C. Antochi, E. Angelino, J. R. Angevaare, F. Arneodo, D. Barge, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, T. Berger, P. A. Breur, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M.R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, G. Eurin, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, A. Gallo Rosso, M. Galloway, F. Gao, L. Grandi, M. Garbini, C. Hasterok, C. Hils, K. Hiraide, L. Hoetzsch, E. Hogenbirk, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. A.M. Lopes, E. López Fune, C. Macolino, J. Mahlstedt, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, A. Molinario, K. Morå, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, V. Pizzella, G. Plante, J. Qin, H. Qiu, D. Ramírez García, S. Reichard, A. Rocchetti, N. Rupp, J. M. F. dos Santos, G. Sartorelli, N. Šarčević, M. Scheibelhut, S. Schindler, J. Schreiner, D. Schulte, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, M. Vargas, G. Volta, O. Wack, H. Wang, Y. Wei, C. Weinheimer, M. Weiss, D. Wenz, J. Westermann, C. Wittweg, J. Wulf, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, J. P. Zopounidis, XENON Collaboration

    European Physical Journal C   81 ( 4 )  2021.04

     View Summary

    The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the 222Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a 222Rn activity concentration of 10μBq/kg in 3.2t of xenon. The knowledge of the distribution of the 222Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the 222Rn activity concentration in XENON1T. The final 222Rn activity concentration of (4.5±0.1)μBq/kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.

    DOI

  • Search for inelastic scattering of WIMP dark matter in XENON1T

    E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, S. Andaloro, E. Angelino, J. R. Angevaare, V. C. Antochi, F. Arneodo, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M.R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. Cuenca, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, M. Galloway, F. Gao, L. Grandi, C. Hils, K. Hiraide, L. Hoetzsch, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, S. Liang, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. Long, J. A.M. Lopes, Y. Ma, C. Macolino, J. Mahlstedt, A. Mancuso, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodan Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, K. Mizukoshi, A. Molinario, K. Morå, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, M. Pierre, V. Pizzella, G. Plante, J. Qi, J. Qin, D. Ramírez Garciá, S. Reichard, A. Rocchetti, N. Rupp, J. M.F. Dos Santos, G. Sartorelli, N. Sarcević, M. Scheibelhut, J. Schreiner, D. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, K. Valerius, M. Vargas, G. Volta, Y. Wei, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, T. Wolf, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, J. P. Zopounidis

    Physical Review D   103 ( 6 )  2021.03

     View Summary

    We report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off Xe129 is the most sensitive probe of inelastic WIMP interactions, with a signature of a 39.6 keV deexcitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.83 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than 2σ. A profile-likelihood ratio analysis is used to set upper limits on the cross section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than 100 GeV/c2, with the strongest upper limit of 3.3×10-39 cm2 for 130 GeV/c2 WIMPs at 90% confidence level.

    DOI

  • Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10GeV/n to 2.2TeV/n with the Calorimetric Electron Telescope on the International Space Station

    O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, M. G. Bagliesi, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, J. Link, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, N. Ospina, S. Ozawa, L. Pacini, F. Palma, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, R. Sparvoli, P. Spillantini, F. Stolzi, S. Sugita, J. E. Suh, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida

    Physical Review Letters   125 ( 25 )  2020.12

    DOI

  • Projected WIMP sensitivity of the XENONnT dark matter experiment

    E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, V. C. Antochi, E. Angelino, J. R. Angevaare, F. Arneodo, D. Barge, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, T. Berger, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M.R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, G. Eurin, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, M. Galloway, F. Gao, L. Grandi, C. Hasterok, C. Hils, K. Hiraide, L. Hoetzsch, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. Long, J. A.M. Lopes, E. López Fune, C. MacOlino, J. Mahlstedt, A. Mancuso, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, K. Mizukoshi, A. Molinario, K. Morå, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, V. Pizzella, G. Plante, J. Qin, H. Qiu, D. Ramírez García, S. Reichard, A. Rocchetti, N. Rupp, J. M.F. Dos Santos, G. Sartorelli, N. Šarčević, M. Scheibelhut, J. Schreiner, D. Schulte, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, K. Valerius, M. Vargas, G. Volta, H. Wang, Y. Wei, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, J. P. Zopounidis

    Journal of Cosmology and Astroparticle Physics   2020 ( 11 )  2020.11

     View Summary

    XENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict the experimental background and project the sensitivity of XENONnT to the detection of weakly interacting massive particles (WIMPs). The expected average differential background rate in the energy region of interest, corresponding to (1, 13) keV and (4, 50) keV for electronic and nuclear recoils, amounts to 12.3 ± 0.6 (keV t y)-1 and (2.2± 0.5)× 10-3 (keV t y)-1, respectively, in a 4 t fiducial mass. We compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. With the exposure goal of 20 t y, the expected sensitivity to spin-independent WIMP-nucleon interactions reaches a cross-section of 1.4×10-48 cm2 for a 50 GeV/c2 mass WIMP at 90% confidence level, more than one order of magnitude beyond the current best limit, set by XENON1T . In addition, we show that for a 50 GeV/c2 WIMP with cross-sections above 2.6×10-48 cm2 (5.0×10-48 cm2) the median XENONnT discovery significance exceeds 3σ (5σ). The expected sensitivity to the spin-dependent WIMP coupling to neutrons (protons) reaches 2.2×10-43 cm2 (6.0×10-42 cm2).

    DOI

  • Excess electronic recoil events in XENON1T

    E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, V. C. Antochi, E. Angelino, J. R. Angevaare, F. Arneodo, D. Barge, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, T. Berger, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M.R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, G. Eurin, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, M. Galloway, F. Gao, L. Grandi, C. Hasterok, C. Hils, K. Hiraide, L. Hoetzsch, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. Long, J. A.M. Lopes, E. López Fune, C. Macolino, J. Mahlstedt, A. Mancuso, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, K. Mizukoshi, A. Molinario, K. Morå, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, V. Pizzella, G. Plante, J. Qin, H. Qiu, D. Ramírez García, S. Reichard, A. Rocchetti, N. Rupp, J. M.F. Dos Santos, G. Sartorelli, N. Šarčević, M. Scheibelhut, J. Schreiner, D. Schulte, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, M. Vargas, G. Volta, H. Wang, Y. Wei, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, J. P. Zopounidis, X. Mougeot, XENON Collaboration

    Physical Review D   102 ( 7 )  2020.10

     View Summary

    We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 0.65 tonne-years and an unprecedentedly low background rate of 76±2stat events/(tonne×year×keV) between 1 and 30 keV, the data enable one of the most sensitive searches for solar axions, an enhanced neutrino magnetic moment using solar neutrinos, and bosonic dark matter. An excess over known backgrounds is observed at low energies and most prominent between 2 and 3 keV. The solar axion model has a 3.4σ significance, and a three-dimensional 90% confidence surface is reported for axion couplings to electrons, photons, and nucleons. This surface is inscribed in the cuboid defined by gae&lt
    3.8×10-12, gaeganeff&lt
    4.8×10-18, and gaegaγ&lt
    7.7×10-22 GeV-1, and excludes either gae=0 or gaegaγ=gaeganeff=0. The neutrino magnetic moment signal is similarly favored over background at 3.2σ, and a confidence interval of μν∈(1.4,2.9)×10-11 μB (90% C.L.) is reported. Both results are in strong tension with stellar constraints. The excess can also be explained by β decays of tritium at 3.2σ significance with a corresponding tritium concentration in xenon of (6.2±2.0)×10-25 mol/mol. Such a trace amount can neither be confirmed nor excluded with current knowledge of its production and reduction mechanisms. The significances of the solar axion and neutrino magnetic moment hypotheses are decreased to 2.0σ and 0.9σ, respectively, if an unconstrained tritium component is included in the fitting. With respect to bosonic dark matter, the excess favors a monoenergetic peak at (2.3±0.2) keV (68% C.L.) with a 3.0σ global (4.0σ local) significance over background. This analysis sets the most restrictive direct constraints to date on pseudoscalar and vector bosonic dark matter for most masses between 1 and 210 keV/c2. We also consider the possibility that Ar37 may be present in the detector, yielding a 2.82 keV peak from electron capture. Contrary to tritium, the Ar37 concentration can be tightly constrained and is found to be negligible.

    DOI

  • Development of a low-α-emitting μ-PIC as a readout device for direction-sensitive dark matter detectors

    Takashi Hashimoto, Kentaro Miuchi, Tomonori Ikeda, Hirohisa Ishiura, Kiseki D. Nakamura, Hiroshi Ito, Koichi Ichimura, Ko Abe, Kazuyoshi Kobayashi, Atsushi Takada, Atsuhiko Ochi, Takuma Nakamura, Takuya Shimada

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   977  2020.10

     View Summary

    © 2020 Elsevier B.V. Direction sensitivity could provide robust evidence for the direct detection of weakly interacting massive particles constituting dark matter. However, the sensitivity of this method remains low due to the radioactive backgrounds. The purpose of this study is to develop a low-background detector as a two-dimensional imaging device for a gaseous time projection chamber. In direction-sensitive dark matter experiments (e.g. NEWAGE), α-rays emitted from the detector components often create substantial radioactive backgrounds. Based on the study of the background of NEWAGE, a new detector “low-αμ-PIC” is developed. The produced μ-PIC performs well as a gas detector and the α-ray emission rate from the μ-PIC reduced by a factor of 100.

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  • Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I

    K. Abe, Y. Chen, K. Hiraide, K. Ichimura, S. Imaizumi, N. Kato, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, K. Sato, H. Sekiya, T. Suzuki, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. H. Kim, R. Ishii, Y. Itow, K. Kanzawa, K. Martens, A. Mason, Y. Suzuki, K. Miuchi, Y. Takeuchi, K. B. Lee, M. K. Lee, Y. Fukuda, H. Ogawa, Y. Kishimoto, K. Nishijima, K. Fushimi, B. D. Xu, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   809  2020.10

     View Summary

    © 2020 The Author(s) We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4×10−12e at 90% confidence level assuming all three species of neutrino have common millicharge. We also set flavor-dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, 7.3×10−12e for νe, 1.1×10−11e for νμ, and 1.1×10−11e for ντ. These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8×10−10 Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the U(1)B−L model of 1.3×10−6 if the dark photon mass is 1×10−3 MeV/c2, and 8.8×10−5 if it is 10 MeV/c2.

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    17
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  • Development of low-background photomultiplier tubes for liquid xenon detectors

    K. Abe, Y. Chen, K. Hiraide, K. Ichimura, S. Imaizumi, N. Kato, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, K. Sato, H. Sekiya, T. Suzuki, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. H. Kim, R. Ishii, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, A. Mason, Y. Suzuki, K. Miuchi, Y. Takeuchi, K. B. Lee, M. K. Lee, Y. Fukuda, H. Ogawa, K. Nishijima, K. Fushimi, B. D. Xu, S. Nakamura

    Journal of Instrumentation   15 ( 9 )  2020.09

     View Summary

    © 2020 IOP Publishing Ltd and Sissa Medialab We successfully developed a new photomultiplier tube (PMT) with a three-inch diameter, convex-shaped photocathode, R13111. Its prominent features include good performance and ultra-low radioactivity. The convex-shaped photocathode realized a large photon acceptance and good timing resolution. Low radioactivity was achieved by three factors: (1) the glass material was synthesized using low-radioactive-contamination material; (2) the photocathode was produced with 39K-enriched potassium; and (3) the purest grade of aluminum material was used for the vacuum seal. As a result each R13111 PMT contains only about 0.4 mBq of 226Ra, less than 2 mBq of 238U, 0.3 mBq of 228Ra, 2 mBq of 40K and 0.2 mBq of 60Co. We also examined and resolved the intrinsic leakage of Xe gas into PMTs that was observed in several older models. We thus succeeded in developing a PMT that has low background, large angular acceptance with high collection efficiency, good timing resolution, and long-term stable operation. These features are highly desirable for experiments searching for rare events beyond the standard model, such as dark matter particle interactions and neutrinoless double beta decay events.

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    5
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  • Energy resolution and linearity of XENON1T in the MeV energy range

    E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, V. C. Antochi, E. Angelino, J. Angevaare, F. Arneodo, D. Barge, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, T. Berger, P. A. Breur, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M.R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, G. Eurin, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, A. Gallo Rosso, M. Galloway, F. Gao, M. Garbini, L. Grandi, C. Hasterok, C. Hils, K. Hiraide, L. Hoetzsch, E. Hogenbirk, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. A.M. Lopes, E. López Fune, C. Macolino, J. Mahlstedt, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, A. Molinario, K. Morå, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, V. Pizzella, G. Plante, J. Qin, H. Qiu, D. Ramírez García, S. Reichard, A. Rocchetti, N. Rupp, J. M.F. dos Santos, G. Sartorelli, N. Šarčević, M. Scheibelhut, S. Schindler, J. Schreiner, D. Schulte, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, M. Vargas, G. Volta, O. Wack, H. Wang, Y. Wei, C. Weinheimer, M. Weiss Xu, D. Wenz, C. Wittweg, J. Wulf, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, J. P. Zopounidis

    European Physical Journal C   80 ( 8 )  2020.08

     View Summary

    Xenon dual-phase time projection chambers designed to search for weakly interacting massive particles have so far shown a relative energy resolution which degrades with energy above ∼ 200 keV due to the saturation effects. This has limited their sensitivity in the search for rare events like the neutrinoless double-beta decay of 136Xe at its Q value, Qββ≃2.46MeV. For the XENON1T dual-phase time projection chamber, we demonstrate that the relative energy resolution at 1σ/μ is as low as (0.80 ± 0.02) % in its one-ton fiducial mass, and for single-site interactions at Qββ. We also present a new signal correction method to rectify the saturation effects of the signal readout system, resulting in more accurate position reconstruction and indirectly improving the energy resolution. The very good result achieved in XENON1T opens up new windows for the xenon dual-phase dark matter detectors to simultaneously search for other rare events.

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  • Measurement of ambient neutrons in an underground laboratory at Kamioka Observatory and future plan

    Keita Mizukoshi, Ryosuke Taishaku, Keishi Hosokawa, Kazuyoshi Kobayashi, Kentaro Miuchi, Tatsuhiro Naka, Atsushi Takeda, Masashi Tanaka, Yoshiki Wada, Kohei Yorita, Sei Yoshida

    Journal of Physics: Conference Series   1468 ( 1 )  2020.03

     View Summary

    © 2020 Published under licence by IOP Publishing Ltd. Ambient neutrons are one of the most serious backgrounds for underground experiments in search of rare events. The ambient neutron flux in an underground laboratory of Kamioka Observatory was measured using a 3He proportional counter with various moderator setups. Since the detector response largely depends on the spectral shape, the energy spectra of the neutrons transported from the rock to the laboratory were estimated by Monte-Carlo simulations. The ratio of the thermal neutron flux to the total neutron flux was found to depend on the thermalizing efficiency of the rock. Thus, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. Consequently, the most-likely neutron spectrum predicted by the simulations for the parameters determined by the experimental results was obtained. The result suggests an interesting spectral shape, which has not been indicated in previous studies. The total ambient neutron flux is [1]. In this paper, we explain our method of the result and discuss our future plan.

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  • Alpha-ray imaging chamber based on a micro-TPC in a low radioactivity structure

    Hiroshi Ito, Kentaro Miuchi, Kazuyoshi Kobayashi, Yasuo Takeuchi, Kiseki D. Nakamura, Tomonori Ikeda, Hirohisa Ishiura

    Journal of Physics: Conference Series   1468 ( 1 )  2020.03

     View Summary

    © 2020 Published under licence by IOP Publishing Ltd. An α-ray imaging chamber has been developed based on a gaseous micro-time-projection chamber with a low-α emission μ-PIC in a low radioactivity structure. The detector offers the advantage of position sensitivity, which allows to image the α-ray contamination for the sample. It measures the α-ray rate in the sample region and a background region at the same time, thus that the net α rate from the sample can be evaluated efficiently by subtracting these rates from each other. In this work, the measurement results for several samples using the detector is provided.

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  • Development of an alpha-particle imaging detector based on a low radioactivity micro-time-projection chamber

    H. Ito, T. Hashimoto, K. Miuchi, K. Kobayashi, Y. Takeuchi, K. D. Nakamura, T. Ikeda, H. Ishiura

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   953  2020.02

     View Summary

    © 2019 Elsevier B.V. An important issue for rare-event-search experiments, such as the search for dark matter or neutrinoless double beta decay, is to reduce radioactivity of the detector materials and the experimental environment. The selection of materials with low radioactive impurities, such as isotopes of the uranium and thorium chains, requires a precise measurement of surface and bulk radioactivity. Focused on the first one, an alpha-particle detector has been developed based on a gaseous micro-time-projection chamber. A low-αμ-PIC with reduced alpha-emission background was installed in the detector. The detector offers the advantage of position sensitivity, which allows the alpha-particle contamination of the sample to be imaged and the background to be measured at the same time. The detector performance was measured by using an alpha-particle source. The measurement with a sample was also demonstrated and the sensitivity is discussed.

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    6
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  • Search for sub-GeV dark matter by annual modulation using XMASS-I detector

    M. Kobayashi, K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, S. Moriyama, M. Nakahata, H. Ogawa, K. Sato, H. Sekiya, T. Suzuki, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, Y. Suzuki, B. D. Xu, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, K. Fushimi, G. Kanzaki, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   795   308 - 313  2019.08

     View Summary

    © 2019 The Author A search for dark matter (DM) with mass in the sub-GeV region (0.32–1 GeV) was conducted by looking for an annual modulation signal in XMASS, a single-phase liquid xenon detector. Inelastic nuclear scattering accompanied by bremsstrahlung emission was used to search down to an electron equivalent energy of 1 keV. The data used had a live time of 2.8 years (3.5 years in calendar time), resulting in a total exposure of 2.38 ton-years. No significant modulation signal was observed and 90% confidence level upper limits of 1.6×10−33 cm2 at 0.5 GeV was set for the DM-nucleon cross section. This is the first experimental result of a search for DM mediated by the bremsstrahlung effect. In addition, a search for DM with mass in the multi-GeV region (4–20 GeV) was conducted with a lower energy threshold than previous analysis of XMASS. Elastic nuclear scattering was used to search down to a nuclear recoil equivalent energy of 2.3 keV, and upper limits of 2.9 ×10−42 cm2 at 8 GeV was obtained.

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  • Search for WIMP- 129 Xe inelastic scattering with particle identification in XMASS-I

    T. Suzuki, K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, H. Ogawa, K. Sato, H. Sekiya, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, Y. Suzuki, B. D. Xu, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, K. Fushimi, G. Kanzaki, S. Nakamura

    Astroparticle Physics   110   1 - 7  2019.07

     View Summary

    © 2019 Elsevier B.V. A search for Weakly Interacting Massive Particles (WIMPs) was conducted with the single-phase liquid-xenon detector XMASS through inelastic scattering in which 129 Xe nuclei were excited, using an exposure (327 kg × 800.0 days) 48 times larger than that of our previous study. The inelastic excitation sensitivity was improved by detailed evaluation of background, event classification based on scintillation timing that distinguished γ-rays and β-rays, and simultaneous fitting of the energy spectra of γ-like and β-like samples. No evidence of a WIMP signal was found. Thus, we set the upper limits of the inelastic channel cross section at 90% confidence level, for example, 4.1×10 −39 cm 2 for a 200 GeV/c 2 WIMP. This result provides the most stringent limits on the SD WIMP-neutron interaction and is better by a factor of 7.7 at 200 GeV/c 2 than the existing experimental limit.

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  • Development of a time projection chamber with a sheet-resistor field cage

    Kentaro Miuchi, Tomonori Ikeda, Hirohisa Ishiura, Kiseki D. Nakamura, Atsushi Takada, Yasuhiro Homma, Ko Abe, Koichi Ichimura, Hiroshi Ito, Kazuyoshi Kobayashi, Takuma Nakamura, Ryuichi Ueno, Takuya Shimada, Takashi Hashimoto, Ryota Yakabe, Atsuhiko Ochi

    Progress of Theoretical and Experimental Physics   2019 ( 6 )  2019.06

     View Summary

    © The Author(s) 2019. A new-concept time projection chamber (TPC) using a commercial resistive sheet, sheet-resistor micro-TPC (SR?-TPC), has been developed and its performance measured. SR?-TPC has the potential to create a more uniform electric field than conventionalTPCs with resistor chains owing to its continuous sheet resistivity, and its production would be easier than that of conventional TPCs. The material used in this study, Achilles-Vynilas, was found to be thin, transparent, and have low radioactivity. A performance test with cosmic muons showed very promising results, including the demonstration of good tracking performance. This type of TPC field cage can offer an alternative for the widely used conventional field cages.

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  • Development of low radioactivity photomultiplier tubes for the XMASS-I detector

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   922   171 - 176  2019.04

     View Summary

    © 2019 Elsevier B.V. XMASS-I is a single-phase liquid xenon detector whose purpose is direct detection of dark matter. To achieve the low background requirements necessary in the detector, a new model of photomultiplier tubes (PMTs), R10789, with a hexagonal window was developed based on the R8778 PMT used in the XMASS prototype detector. We screened the numerous component materials for their radioactivity. During development, the largest contributions to the reduction of radioactivity came from the stem and the dynode support. The glass stem was exchanged to the Kovar alloy one and the ceramic support were changed to the quartz one. R10789 is the first model of Hamamatsu Photonics K. K. that adopted these materials for low background purposes and provided a groundbreaking step for further reductions of radioactivity in PMTs. Measurements with germanium detectors showed 1.2 ± 0.3 mBq/PMT of 226 Ra, less than 0.78 mBq/PMT of 228 Ra, 9.1 ± 2.2 mBq/PMT of 40 K, and 2.8 ± 0.2 mBq/PMT of 60 Co. In this paper, the radioactive details of the developed R10789 are described together with our screening methods and the components of the PMT.

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    14
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  • A direct dark matter search in XMASS-I

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   789   45 - 53  2019.02

     View Summary

    © 2018 The Author A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We have used 705.9 live days of data in a fiducial volume containing 97kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was (4.2±0.2)×10−3day−1kg−1keVee−1 at 5keVee, with a signal efficiency of 20%. All the remaining events are consistent with our background evaluation, mostly of the “mis-reconstructed events” originated from 210Pb in the copper plates lining the detector's inner surface. The obtained upper limit on a spin-independent WIMP-nucleon cross section was 2.2×10−44cm2 for a WIMP mass of 60GeV/c2 at the 90% confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors.

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  • Dark matter searches in XMASS

    Kazuyoshi Kobayashi

    Proceedings of Science   340  2019

     View Summary

    © 2019 Sissa Medialab Srl. All rights reserved. With 835 kg liquid xenon, XMASS searched for various kinds of dark matter candidate. From November 2013, we have been taking data for more than 4.5 years. We report standard WIMP, annual modulation, hidden photon and axion-like particle searches. No significant signals are observed in these searches.

  • A measurement of the scintillation decay time constant of nuclear recoils in liquid xenon with the XMASS-I detector

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, H. Ogawa, K. Sato, H. Sekiya, T. Suzuki, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, Y. Suzuki, B. D. Xu, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, K. Fushimi, G. Kanzaki, S. Nakamura

    Journal of Instrumentation   13 ( 12 )  2018.12

     View Summary

    © 2018 The Author(s). We report an in-situ measurement of the nuclear recoil (NR) scintillation decay time constant in liquid xenon (LXe) using the XMASS-I detector at the Kamioka underground laboratory in Japan. XMASS-I is a large single-phase LXe scintillation detector whose purpose is the direct detection of dark matter via NR which can be induced by collisions between Weakly Interacting Massive Particles (WIMPs) and a xenon nucleus. The inner detector volume contains 832 kg of LXe. 252 Cf was used as an external neutron source for irradiating the detector. The scintillation decay time constant of the resulting neutron induced NR was evaluated by comparing the observed photon detection times with Monte Carlo simulations. Fits to the decay time prefer two decay time components, one for each of the Xe 2∗ singlet and triplet states, with τ S = 4.3 ± 0.6 ns taken from prior research, τ T was measured to be 26.9 +0.7-1.1 ns with a singlet state fraction F S of 0.252 +0.027-0.019 . We also evaluated the performance of pulse shape discrimination between NR and electron recoil (ER) with the aim of reducing the electromagnetic background in WIMP searches. For a 50% NR acceptance, the ER acceptance was 13.7±1.0% and 4.1±0.7% in the energy ranges of 5-10 keV ee and 10-15 keV ee , respectively.

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  • Search for dark matter in the form of hidden photons and axion-like particles in the XMASS detector

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, H. Ogawa, K. Sato, H. Sekiya, T. Suzuki, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, K. Masuda, K. Martens, Y. Suzuki, B. D. Xu, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, K. Fushimi, G. Kanzaki, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   787   153 - 158  2018.12

     View Summary

    © 2018 The Author Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the α′/α parameter related to kinetic mixing of hidden photons and the coupling constant gAe of axion-like particles in the mass range from 40 to 120 keV/c2, resulting in α′/α<6×10−26 and gAe<4×10−13. These limits are the most stringent over this mass range derived from both direct and indirect searches to date.

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    33
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  • Development of a surface alpha ray detector based on μ-TPC with low background

    H. Ito, T. Hashimoto, T. Ikeda, H. Ishiura, K. Miuchi, K. D. Nakamura, Y. Takeuchi, K. Kobayashi

    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2018 - Proceedings    2018.11

     View Summary

    © 2018 IEEE. Radioactive impurities in the detector material have been focused as the serious background in a search for a dark matter. In order to select a pure material which have a low radioactive impurity such as nuclear in uranium-chain and thorium-chain, a precise measurement of radioactivity has been required. A new alpha-ray detector has been developed based on a gaseous μ-TPC. A low-α μ-PIC was installed to the detector for low background measurement. The detector has advantages of a position sensitivity and a ability to take sample and background event on a same time. We performed to calibrate the energy, to evaluate resolution using an alpha-ray source, to inspect a sample as a part of a conventional μ-PIC as a demonstration.

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  • Direct dark matter search by annual modulation with 2.7 years of XMASS-I data

    K.Abe, K.Hiraide, K.Ichimura, Y.Kishimoto, K.Kobayashi, M.Kobayashi, S.Moriyama, M.Nakahata, T.Norita, H.Ogawa, K.Sato, H.Sekiya, O.Takachio, A.Takeda, S.Tasaka, M.Yamashita, B.S.Yang, N.Y.Kim, Y.D.Kim, Y.Itow, K.Kanzawa, R.Kegasa, K.Masuda, H.Takiya, K.Fushimi, G.Kanzaki, K.Martens, Y.Suzuki, B.D.Xu, R.Fujita, K.Hosokawa, K.Miuchi, N.Oka, Y.Takeuchi, Y.H.Kim, K.B.Lee, M.K.Lee, Y.Fukuda, M.Miyasaka, K.Nishijima, S.Nakamura, MASS Collaboration

    Physical Review D   97 ( 10 ) 102006  2018.05  [Refereed]

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  • Direct dark matter search by annual modulation with 2.7 years of XMASS-I data DIRECT DARK MATTER SEARCH by ANNUAL ⋯ K. ABE et al.

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Physical Review D   97 ( 10 )  2018.05

     View Summary

    © 2018 American Physical Society. An annual modulation signal due to the Earth orbiting around the Sun would be one of the strongest indications of the direct detection of dark matter. In 2016, we reported a search for dark matter by looking for this annual modulation with our single-phase liquid xenon XMASS-I detector. That analysis resulted in a slightly negative modulation amplitude at low energy. In this work, we included more than one year of additional data, which more than doubles the exposure to 800 live days with the same 832 kg target mass. When we assume weakly interacting massive particle (WIMP) dark matter elastically scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon cross section was improved by a factor of 2 to 1.9×10-41 cm2 at 8 GeV/c2 at 90% confidence level with our newly implemented data selection through a likelihood method. For the model-independent case, without assuming any specific dark matter model, we obtained more consistency with the null hypothesis than before with a p-value of 0.11 in the 1-20 keV energy region. This search probed this region with an exposure that was larger than that of DAMA/LIBRA. We also did not find any significant amplitude in the data for periodicity with periods between 50 and 600 days in the energy region between 1 to 6 keV.

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  • Improved search for two-neutrino double electron capture on 124Xe and 126Xe using particle identification in XMASS-I

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Progress of Theoretical and Experimental Physics   2018 ( 5 )  2018.05

     View Summary

    © The Author(s) 2018. We conducted an improved search for the simultaneous capture of two K-shell electrons on the 124Xe and 126Xe nuclei with emission of two neutrinos using 800.0 days of data from the XMASS-I detector. A novel method to discriminate γ -ray/X-ray or double electron capture signals from β-ray background using scintillation time profiles was developed for this search. No significant signal was found when fitting the observed energy spectra with the expected signal and background. Therefore, we set the most stringent lower limits on the half-lives at 2.1 × 1022 and 1.9 × 1022 years for 124Xe and 126Xe, respectively, with 90% confidence level. These limits improve upon previously reported values by a factor of 4.5.

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    17
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  • Identification of 210Pb and 210Po in the bulk of copper samples with a low-background alpha particle counter

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   884   157 - 161  2018.03

     View Summary

    © 2017 Elsevier B.V. We established a method to assay 210Pb and 210Po contaminations in the bulk of copper samples using a low-background alpha particle counter. The achieved sensitivity for the 210Pb and 210Po contaminations reaches a few mBq/kg. Due to this high sensitivity, the 210Pb and 210Po contaminations in oxygen free copper bulk were identified and measured for the first time. The 210Pb contaminations of our oxygen free copper samples were 17–40 mBq/kg. Based on our investigation of copper samples in each production step, the 210Pb in oxygen free copper was understood to be a small residual of an electrolysis process. This method to measure bulk contaminations of 210Pb and 210Po could be applied to other materials.

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    25
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  • Identification of 210Pb and 210Po in the bulk of copper samples with a low-background alpha particle counter

    Kazuyoshi Kobayashi

    AIP Conference Proceedings   1921  2018.01

     View Summary

    © 2018 Author(s). We established a method to assay 210Pb and 210Po contaminations in the bulk of copper samples using a low-background alpha particle counter. The achieved sensitivity for the 210Pb and 210Po contaminations reaches a few mBq/kg. Due to this high sensitivity, the 210Pb and 210Po contaminations in oxygen free copper bulk were identified and measured for the first time. The 210Pb contaminations of our oxygen free copper samples were 17-40 mBq/kg. Based on our investigation of copper samples in each production step, the 210Pb in oxygen free copper was understood to be a small residual of an electrolysis process. This method to measure bulk contaminations of 210Pb and 210Po could be applied to other materials.

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  • Measurement of ambient neutrons in an underground laboratory at the Kamioka Observatory

    Keita Mizukoshi, Ryosuke Taishaku, Keishi Hosokawa, Kazuyoshi Kobayashi, Kentaro Miuchi, Tatsuhiro Naka, Atsushi Takeda, Masashi Tanaka, Yoshiki Wada, Kohei Yorita, Sei Yoshida

    Progress of Theoretical and Experimental Physics   2018 ( 12 )  2018

     View Summary

    © The Author(s) 2018. Published by Oxford University Press on behalf of the Physical Society of Japan. Ambient neutrons are one of the most serious backgrounds for underground experiments searching for rare events. The ambient neutron flux in an underground laboratory at the Kamioka Observatory was measured using a 3 He proportional counter with various moderator setups. Since the detector response largely depends on the spectral shape, the energy spectra of the neutrons transported from the rock to the laboratory were estimated by Monte Carlo simulations. The ratio of the thermal neutron flux to the total neutron flux was found to depend on the ther-malizing efficiency of the rock. Therefore, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. Consequently, the most likely neutron spectrum predicted by the simulations for the parameters determined by the experimental results was obtained. The result suggests an interesting spectral shape, which has not been indicated in previous studies. The total ambient neutron flux is (23.5 ± 0.7 stat.+−1.92.1 sys. ) × 10 −6 cm −2 s −1 . This result, especially the energy spectrum information, could be a new and important input for estimating the background in current and future experiments in the underground laboratory at the Kamioka Observatory.

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    7
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  • Search for solar Kaluza-Klein axions by annual modulation with the XMASS-I detector

    N. Oka, K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, K. Sato, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, K. Kanzawa, R. Kegasa, K. Masuda, H. Takiya, K. Fushimi, G. Kanzaki, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, Y. Fukuda, M. Miyasaka, K. Nishijima, S. Nakamura

    Progress of Theoretical and Experimental Physics   2017 ( 10 )  2017.10

     View Summary

    © The Author(s) 2017. Published by Oxford University Press on behalf of the Physical Society of Japan. In theories with large extra dimensions beyond the standard 4-dimensional spacetime, axions could propagate in such extra dimensions, and acquire Kaluza-Klein (KK) excitations. These KK axions are produced in the Sun and could solve the unexplained heating of the solar corona. While most of the solar KK axions escape from the solar system, a small fraction are gravitationally trapped in orbits around the Sun. They would decay into 2 photons inside a terrestrial detector. The event rate is expected to modulate annually depending on the distance from the Sun. We have searched for the annual modulation signature using 832 × 359 kg·days of XMASS-I data. No significant event rate modulation is found, and hence we set the first experimental constraint on the KK axion-photon coupling of 4.8 × 10 −12 GeV −1 at the 90% confidence level for a KK axion number density of n¯ a = 4.07 × 10 13 m −3 , the total number of extra dimensions n = 2, and the number of extra dimensions δ = 2 that axions can propagate in.

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    11
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  • Detectability of galactic supernova neutrinos coherently scattered on xenon nuclei in XMASS

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, T. Norita, H. Ogawa, H. Sekiya, O. Takachio, A. Takeda, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, S. Tasaka, J. Liu, K. Martens, Y. Suzuki, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Onishi, Y. Takeuchi, Y. H. Kim, J. S. Lee, K. B. Lee, M. K. Lee, Y. Fukuda, Y. Itow, R. Kegasa, K. Kobayashi, K. Masuda, H. Takiya, H. Uchida, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura, XMASS Collaboration

    Astroparticle Physics   89   51 - 56  2017.03

     View Summary

    © 2017 Elsevier B.V. The coherent elastic neutrino-nucleus scattering (CEvNS) plays a crucial role at the final evolution of stars. The detection of it would be of importance in astroparticle physics. Among all available neutrino sources, galactic supernovae give the highest neutrino flux in the MeV range. Among all liquid xenon dark matter experiments, XMASS has the largest sensitive volume and light yield. The possibility to detect galactic supernova via the CEvNS-process on xenon nuclei in the current XMASS detector was investigated. The total number of events integrated in about 18 s after the explosion of a supernova 10 kpc away from the Earth was expected to be from 3.5 to 21.1, depending on the supernova model used to predict the neutrino flux, while the number of background events in the same time window was measured to be negligible. All lead to very high possibility to detect CEvNS experimentally for the first time utilizing the combination of galactic supernovae and the XMASS detector. In case of a supernova explosion as close as Betelgeuse, the total observable events can be more than ∼ 104, making it possible to distinguish different supernova models by examining the evolution of neutrino event rate in XMASS.

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    22
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  • A measurement of the time profile of scintillation induced by low energy gamma-rays in liquid xenon with the XMASS-I detector

    H. Takiya, K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, H. Sekiya, O. Takachio, A. Takeda, S. Tasaka, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, Y. Itow, R. Kegasa, K. Kobayashi, K. Masuda, K. Fushimi, K. Martens, Y. Suzuki, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Onishi, Y. Takeuchi, Y. H. Kim, J. S. Lee, K. B. Lee, M. K. Lee, Y. Fukuda, K. Nishijima, S. Nakamura, XMASS Collaboration

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   834   192 - 196  2016.10

     View Summary

    © 2016 Elsevier B.V. We report the measurement of the emission time profile of scintillation from gamma-ray induced events in the XMASS-I 832 kg liquid xenon scintillation detector. Decay time constant was derived from a comparison of scintillation photon timing distributions between the observed data and simulated samples in order to take into account optical processes such as absorption and scattering in liquid xenon. Calibration data of radioactive sources, 55Fe, 241Am, and 57Co were used to obtain the decay time constant. Assuming two decay components, τ1 and τ2, the decay time constant τ2 increased from 27.9 ns to 37.0 ns as the gamma-ray energy increased from 5.9 keV to 122 keV. The accuracy of the measurement was better than 1.5 ns at all energy levels. A fast decay component with τ1∼2ns was necessary to reproduce data. Energy dependencies of τ2 and the fraction of the fast decay component were studied as a function of the kinetic energy of electrons induced by gamma-rays. The obtained data almost reproduced previously reported results and extended them to the lower energy region relevant to direct dark matter searches.

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    19
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  • Search for two-neutrino double electron capture on 124Xe with the XMASS-I detector

    K. Abea, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, T. Norita, H. Ogawa, H. Sekiya, O. Takachio, A. Takeda, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, S. Tasaka, J. Liud, K. Martens, Y. Suzuki, R. Fujita, K. Hosokawa, K. Miuchi, N. Oka, Y. Onishi, Y. Takeuchi, Y. H. Kim, J. S. Lee, K. B. Lee, M. K. Lee, Y. Fukuda, Y. Itow, R. Kegasa, K. Kobayashi, K. Masuda, H. Takiya, H. Uchidai, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   759   64 - 68  2016.08

     View Summary

    © 2016 The Author(s). Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on 124Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as 4.7×1021 years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the 126Xe two-neutrino double electron capture half-life of 4.3×1021 years at 90% confidence level as well.

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    10
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  • Direct dark matter search by annual modulation in XMASS-I

    K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, M. Nakahata, T. Norita, H. Ogawa, H. Sekiya, O. Takachio, A. Takeda, M. Yamashita, B. S. Yang, N. Y. Kim, Y. D. Kim, S. Tasaka, K. Fushimi, J. Liu, K. Martens, Y. Suzuki, B. D. Xu, R. Fujita, K. Hosokawa, K. Miuchi, Y. Onishi, N. Oka, Y. Takeuchi, Y. H. Kim, J. S. Lee, K. B. Lee, M. K. Lee, Y. Fukuda, Y. Itow, R. Kegasa, K. Kobayashi, K. Masuda, H. Takiya, K. Nishijima, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   759   272 - 276  2016.08

     View Summary

    © 2016 The Author(s). A search for dark matter was conducted by looking for an annual modulation signal due to the Earth's rotation around the Sun using XMASS, a single phase liquid xenon detector. The data used for this analysis was 359.2 live days times 832 kg of exposure accumulated between November 2013 and March 2015. When we assume Weakly Interacting Massive Particle (WIMP) dark matter elastically scattering on the target nuclei, the exclusion upper limit of the WIMP-nucleon cross section 4.3×10-41 cm2 at 8 GeV/c2 was obtained and we exclude almost all the DAMA/LIBRA allowed region in the 6 to 16 GeV/c2 range at ~10-40 cm2. The result of a simple modulation analysis, without assuming any specific dark matter model but including electron/γ events, showed a slight negative amplitude. The p-values obtained with two independent analyses are 0.014 and 0.068 for null hypothesis, respectively. We obtained 90% C.L. upper bounds that can be used to test various models. This is the first extensive annual modulation search probing this region with an exposure comparable to DAMA/LIBRA.

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    43
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  • Using 220Rn to calibrate liquid noble gas detectors

    M. Kobayashi, M. Yamashita, A. Takeda, K. Kishimoto, S. Moriyama

    Journal of Physics: Conference Series   718 ( 4 )  2016.06

     View Summary

    In this paper, we describe 220Rn calibration source that was developed for liquid noble gas detectors. The key advantage of this source is that it can provide 212Bi-212 Po consecutive events, which enables us to evaluate the vertex resolution of a detector at low energy by comparing low-energy events of 212Bi and corresponding higher-energy α-rays from 212Po. Since 220Rn is a noble gas, a hot metal getter can be used when introduced using xenon as the carrier gas. In addition, no long-life radioactive isotopes are left behind in the detector after the calibration is complete
    this has clear advantage over the use of 222Rn which leaves longlife radioactivity, i.e., 210Pb. Using a small liquid xenon test chamber, we developed a system to introduce 220Rn via the xenon carrier gas
    we demonstrated the successful introduction of 6 ×102 220Rn atoms in our test environment.

    DOI

  • Direct dark matter search with XMASS: Modulation analysis

    Kazuyoshi Kobayashi

    Journal of Physics: Conference Series   718 ( 4 )  2016.06

     View Summary

    © Published under licence by IOP Publishing Ltd. Dark matter search by means of the annual modulation was done using large single-phase liquid-xenon detector, XMASS. With the data from November-2013 to March-2015, model independent analysis showed a weak modulation effect, however, the result can be explained by a fluctuation of the background at the level of 7-17%. If we assume the standard weekly interacting massive particles dark matter, we exclude almost all the allowed region claimed by the DAMA/LIBRA experiment. This is the first extensive search over their allowed region exploiting the annual modulation with high statistics data.

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  • Direct Dark Matter Search with XMASS

    Kazuyoshi Kobayashi

    Nuclear and Particle Physics Proceedings   273-275   361 - 366  2016.04

     View Summary

    © 2016 . The purpose of current XMASS project is dark matter detection. With 835 kg liquid xenon, we searched for various kinds of dark matter candidate using commissioning data. In order to reduce the background contribution from the PMT surface material, we have refurbished the detector and restarted to take data in November, 2013. Future project of XMASS is also shown.

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  • Surface purity control during XMASS detector refurbishment

    Kazuyoshi Kobayashi

    AIP Conference Proceedings   1672  2015.08

     View Summary

    © 2015 AIP Publishing LLC. The XMASS project aims at detecting dark matter, pp and 7Be solar neutrinos, and neutrino less double beta decay using large volume of pure liquid xenon. The first physics target of the XMASS project is to detect dark matter with 835 kg liquid xenon. After the commissioning runs, XMASS detector was refurbished to minimize the background contribution mainly from PMT sealing material and we restarted data taking in November 2013. We report how we control surface purity, especially how we prevent radon daughter accumulation on the detector copper surface, during XMASS detector refurbishment. The result and future plan of XMASS are also reported.

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    3
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  • Micro-source development for XMASS experiment

    N. Y. Kim, K. Abe, K. Hieda, K. Hiraide, S. Hirano, Y. Kishimoto, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Nishiie, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, K. Ueshima, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, Y. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, Y. Nishitani, K. Masuda, H. Takiya, H. Uchida, Y. D. Kim, F. Kusaba, D. Motoki, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   784   499 - 503  2015.06

     View Summary

    © 2014 Elsevier B.V. All rights reserved. XMASS is a multipurpose liquid-xenon detector that currently aims to directly detect dark matter. In this paper, we describe the fabrication and characterization of reference sources used for the energy calibration and position reconstruction of the present XMASS detector. Several gamma-ray sources were produced in the form of a sealed needle-source. A thin-wall tube with a diameter of approximately 0.2 mm was sealed at both ends, with the 241Am or 57Co source material contained inside. The active region of the source was observed to be 1-2 mm long, close to the tip of the needle. These sources were tested in the XMASS detector, and the results were compared with Monte-Carlo simulations.

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    15
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  • Search for n-n ¯ oscillation in Super-Kamiokande SEARCH FOR n-n ¯ OSCILLATION IN SUPER-⋯ K. ABE et al.

    K. Abe, Y. Hayato, T. Iida, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, H. Watanabe, I. Higuchi, C. Ishihara, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, F. Dufour, A. Herfurth, E. Kearns, S. Likhoded, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, J. Dunmore, J. Griskevich, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, B. Hartfiel, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeoung, J. Y. Kim, I. T. Lim, K. Scholberg, N. Tanimoto, C. W. Walter, R. Wendell, R. W. Ellsworth, S. Tasaka, G. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, K. Nitta, Y. Oyama, A. T. Suzuki, M. Hasegawa, H. Maesaka, T. Nakaya, T. Sasaki, H. Sato, H. Tanaka, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, G. W. Sullivan, R. Gran, A. Habig, Y. Fukuda, Y. Itow

    Physical Review D - Particles, Fields, Gravitation and Cosmology   91 ( 7 )  2015.04

     View Summary

    © 2015 American Physical Society. A search for neutron-antineutron (n-n¯) oscillation was undertaken in Super-Kamiokande using the 1489 live-day or 2.45×1034 neutron-year exposure data. This process violates both baryon and baryon minus lepton numbers by an absolute value of two units and is predicted by a large class of hypothetical models where the seesaw mechanism is incorporated to explain the observed tiny neutrino masses and the matter-antimatter asymmetry in the Universe. No evidence for n-n¯ oscillation was found; the lower limit of the lifetime for neutrons bound in O16, in an analysis that included all of the significant sources of experimental uncertainties, was determined to be 1.9×1032years at the 90% confidence level. The corresponding lower limit for the oscillation time of free neutrons was calculated to be 2.7×108s using a theoretical value of the nuclear suppression factor of 0.517×1023s-1 and its uncertainty.

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    92
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  • Development and operational experience of magnetic horn system for T2K experiment

    T. Sekiguchi, K. Bessho, Y. Fujii, M. Hagiwara, T. Hasegawa, K. Hayashi, T. Ishida, T. Ishii, H. Kobayashi, T. Kobayashi, S. Koike, K. Koseki, T. Maruyama, H. Matsumoto, T. Nakadaira, K. Nakamura, K. Nakayoshi, K. Nishikawa, Y. Oyama, K. Sakashita, M. Shibata, Y. Suzuki, M. Tada, K. Takahashi, T. Tsukamoto, Y. Yamada, Y. Yamanoi, H. Yamaoka, A. K. Ichikawa, H. Kubo, Z. Butcher, S. Coleman, A. Missert, J. Spitz, E. D. Zimmerman, M. Tzanov, L. Bartoszek

    Nucl.Instrum.Meth.A   789   57 - 80  2015.02  [Refereed]

     View Summary

    A magnetic horn system to be operated at a pulsed current of 320 kA and to
    survive high-power proton beam operation at 750 kW was developed for the T2K
    experiment. The first set of T2K magnetic horns was operated for over 12
    million pulses during the four years of operation from 2010 to 2013, under a
    maximum beam power of 230 kW, and $6.63\times10^{20}$ protons were exposed to
    the production target. No significant damage was observed throughout this
    period. This successful operation of the T2K magnetic horns led to the
    discovery of the $\nu_{\mu}\rightarrow\nu_e$ oscillation phenomenon in 2013 by
    the T2K experiment. In this paper, details of the design, construction, and
    operation experience of the T2K magnetic horns are described.

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  • Physics potential of a long-baseline neutrino oscillation experiment using a J-PARC neutrino beam and Hyper-Kamiokande

    K. Abe, H. Aihara, C. Andreopoulos, I. Anghel, A. Ariga, T. Ariga, R. Asfandiyarov, M. Askins, J. J. Back, P. Ballett, M. Barbi, G. J. Barker, G. Barr, F. Bay, P. Beltrame, V. Berardi, M. Bergevin, S. Berkman, T. Berry, S. Bhadra, F. D.M. Blaszczyk, A. Blondel, S. Bolognesi, S. B. Boyd, A. Bravar, C. Bronner, F. S. Cafagna, G. Carminati, S. L. Cartwright, M. G. Catanesi, K. Choi, J. H. Choi, G. Collazuol, G. Cowan, L. Cremonesi, G. Davies, G. De Rosa, C. Densham, J. Detwiler, D. Dewhurst, F. Di Lodovico, S. Di Luise, O. Drapier, S. Emery, A. Ereditato, P. Fernández, T. Feusels, A. Finch, M. Fitton, M. Friend, Y. Fujii, Y. Fukuda, D. Fukuda, V. Galymov, K. Ganezer, M. Gonin, P. Gumplinger, D. R. Hadley, L. Haegel, A. Haesler, Y. Haga, B. Hartfiel, M. Hartz, Y. Hayato, M. Hierholzer, J. Hill, A. Himmel, S. Hirota, S. Horiuchi, K. Huang, A. K. Ichikawa, T. Iijima, M. Ikeda, J. Imber, K. Inoue, J. Insler, R. A. Intonti, T. Irvine, T. Ishida, H. Ishino, M. Ishitsuka, Y. Itow, A. Izmaylov, B. Jamieson, H. I. Jang, M. Jiang, K. K. Joo, C. K. Jung, A. Kaboth, T. Kajita, J. Kameda, Y. Karadhzov, T. Katori, E. Kearns, M. Khabibullin, A. Khotjantsev, J. Y. Kim, S. B. Kim, Y. Kishimoto, T. Kobayashi

    Progress of Theoretical and Experimental Physics   2015 ( 5 )  2015

     View Summary

    Hyper-Kamiokande will be a next-generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of CP asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long-baseline neutrino experiment using the Hyper- Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5MW ×107s integrated proton beam power (corresponding to 1.56 × 1022protons on target with a 30 GeV proton beam) to a 2.5° off-axis neutrino beam, it is expected that the leptonic CP phase δCPcan be determined to better than 19 degrees for all possible values of δCP, and CP violation can be established with a statistical significance of more than 3 σ (5 σ) for 76% (58%) of the δCPparameter space. Using both νeappearance and νμ disappearance data, the expected 1 σ uncertainty of sin2Θ23is 0.015(0.006) for sin2Θ23= 0.5(0.45).

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  • Search for bosonic superweakly interacting massive dark matter particles with the XMASS-I detector

    K. Abe, K. Hieda, K. Hiraide, S. Hirano, Y. Kishimoto, K. Ichimura, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, Y. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, K. Masuda, H. Takiya, H. Uchida, N. Y. Kim, Y. D. Kim, F. Kusaba, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Physical Review Letters   113 ( 12 )  2014.09

     View Summary

    © 2014 American Physical Society. Bosonic superweakly interacting massive particles (super-WIMPs) are a candidate for warm dark matter. With the absorption of such a boson by a xenon atom, these dark matter candidates would deposit an energy equivalent to their rest mass in the detector. This is the first direct detection experiment exploring the vector super-WIMPs in the mass range between 40 and 120 keV. With the use of 165.9 day of data, no significant excess above background was observed in the fiducial mass of 41 kg. The present limit for the vector super-WIMPs excludes the possibility that such particles constitute all of dark matter. The absence of a signal also provides the most stringent direct constraint on the coupling constant of pseudoscalar super-WIMPs to electrons. The unprecedented sensitivity was achieved exploiting the low background at a level 10-4kg-1keVee-1day-1 in the detector.

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  • Search for inelastic WIMP nucleus scattering on 129Xe in data from the XMASS-I experiment

    H. Uchida, K. Abe, K. Hieda, K. Hiraide, S. Hirano, K. Ichimura, Y. Kishimoto, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, Y. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, K. Masuda, Y. Nishitani, H. Takiya, N. Y. Kim, Y. D. Kim, F. Kusaba, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Progress of Theoretical and Experimental Physics   2014 ( 6 )  2014.06

     View Summary

    A search for inelastic scattering of weakly interacting massive particles (WIMPs) on the isotope 129Xewas done in data taken with the single-phase liquid-xenon detectorXMASSat the Kamioka Observatory. Using a restricted volume containing 41 kg of liquid xenon at the very center of our detector, we observed no significant excess of events in 165.9 live days of data. Our background reduction allowed us to derive our limits without explicitly subtracting the remaining events that are compatible with background expectations. As an example, we derive for a 50 GeV WIMP an upper limit of 3.2 pb at the 90% confidence level for its inelastic cross section on 129Xe nuclei.

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  • Search for dinucleon decay into kaons in super-kamiokande

    M. Litos, K. Abe, Y. Hayato, T. Iida, M. Ikeda, K. Iyogi, J. Kameda, K. Kobayashi, Y. Koshio, Y. Kozuma, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, T. Yokozawa, S. Hazama, C. Ishihara, H. Kaji, T. Kajita, K. Kaneyuki, T. McLachlan, K. Okumura, Y. Shimizu, N. Tanimoto, M. R. Vagins, E. Kearns, J. L. Stone, L. R. Sulak, F. Dufour, J. L. Raaf, B. Henning, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, J. B. Albert, T. Wongjirad, R. Wendell, K. Scholberg, C. W. Walter, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, H. Nishino, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. Minamino, T. Nakaya, Y. Fukuda, Y. Itow, G. Mitsuka, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, R. Terri, C. Yanagisawa, N. Tamura, H. Ishino, A. Kibayashi, S. Mino, T. Mori, M. Sakuda, H. Toyota, Y. Kuno, M. Yoshida

    Physical Review Letters   112 ( 13 )  2014.04

     View Summary

    A search for the dinucleon decay pp→K+K+ has been performed using 91.6kton·yr data from Super-Kamiokande-I. This decay provides a sensitive probe of the R-parity-violating parameter λ112′′. A boosted decision tree analysis found no signal candidates in the data. The expected background was 0.28±0.19 atmospheric neutrino induced events and the estimated signal detection efficiency was 12.6%±3.2%. A lower limit of 1.7×1032years has been placed on the partial lifetime of the decay O16→C14K+K+ at 90% C.L. A corresponding upper limit of 7.8×10-9 has been placed on the parameter λ112′′. © 2014 American Physical Society.

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  • Search for solar axions in xmass, A large liquid-xenon detector

    K. Abe, K. Hieda, K. Hiraide, S. Hiranoa, Y. Kishimoto, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, K. Ueshima, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, K. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, K. Masuda, Y. Nishitani, H. Takiya, H. Uchida, N. Y. Kim, Y. D. Kim, F. Kusabaj, D. Motoki, K. Nishijimaj, K. Fujii, I. Murayama, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   724 ( 1-3 ) 46 - 50  2013.07

     View Summary

    © 2013 Elsevier B.V. XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6 ton days of liquid xenon, the model-independent limit on the coupling for mass ≪1 keV is |gaee| < 5.4 x 10-1 1 (90% C.L.), which is a factor of two stronger than the existing experimental limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are 1.9 and 250 eV, respectively. In the mass range of 10-40 keV, this study produced the most stringent limit, which is better than that previously derived from astrophysical arguments regarding the Sun to date.

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  • Light WIMP search in XMASS

    K. Abe, K. Hieda, K. Hiraide, S. Hirano, Y. Kishimoto, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, K. Ueshima, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, Y. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, K. Masuda, Y. Nishitani, H. Takiya, H. Uchida, N. Y. Kim, Y. D. Kim, F. Kusaba, D. Motoki, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   719 ( 1-3 ) 78 - 82  2013.02

     View Summary

    A search for light dark matter using low-threshold data from the single phase liquid xenon scintillation detector XMASS, has been conducted. Using the entire 835 kg inner volume as target, the analysis threshold can be lowered to 0.3 keVee (electron-equivalent) to search for light dark matter. With low-threshold data corresponding to a 5591.4 kg day exposure of the detector and without discriminating between nuclear-recoil and electronic events, XMASS excludes part of the parameter space favored by other experiments. © 2013 Elsevier B.V.

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  • XMASS detector

    K. Abe, K. Hieda, K. Hiraide, S. Hirano, Y. Kishimoto, K. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, H. Nishiie, H. Ogawa, N. Oka, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, O. Takachio, K. Ueshima, D. Umemoto, M. Yamashita, B. S. Yang, S. Tasaka, J. Liu, K. Martens, K. Hosokawa, K. Miuchi, A. Murata, Y. Onishi, Y. Otsuka, Y. Takeuchi, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee, Y. Fukuda, Y. Itow, Y. Nishitani, K. Masuda, H. Takiya, H. Uchida, N. Y. Kim, Y. D. Kim, F. Kusaba, D. Motoki, K. Nishijima, K. Fujii, I. Murayama, S. Nakamura

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   716   78 - 85  2013

     View Summary

    The XMASS project aims to detect dark matter, pp and 7Be solar neutrinos, and neutrinoless double beta decay using ultra pure liquid xenon. The first phase of the XMASS experiment searches for dark matter. In this paper, we describe the XMASS detector in detail, including its configuration, data acquisition equipment and calibration system. © 2013 Elsevier B.V.

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  • Self-shielding effect of a single phase liquid xenon detector for direct dark matter search

    A. Minamino, K. Abe, Y. Ashie, J. Hosaka, K. Ishihara, K. Kobayashi, Y. Koshio, C. Mitsuda, S. Moriyama, M. Nakahata, Y. Nakajima, T. Namba, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Taki, K. Ueshima, Y. Ebizuka, A. Ota, S. Suzuki, H. Hagiwara, Y. Hashimoto, S. Kamada, M. Kikuchi, N. Kobayashi, T. Nagase, S. Nakamura, K. Tomita, Y. Uchida, Y. Fukuda, T. Sato, K. Nishijima, T. Maruyama, D. Motoki, Y. Itow, Y. D. Kim, J. I. Lee, S. H. Moon, K. E. Lim, J. P. Cravens, M. B. Smy

    Astroparticle Physics   35 ( 10 ) 609 - 614  2012.05

     View Summary

    Liquid xenon is a suitable material for a dark matter search. For future large scale experiments, single phase detectors are attractive due to their simple configuration and scalability. However, in order to reduce backgrounds, they need to fully rely on liquid xenon's self-shielding property. A prototype detector was developed at Kamioka Observatory to establish vertex and energy reconstruction methods and to demonstrate the self-shielding power against γ-rays from outside of the detector. 662 keV γ-rays from 137Cs are attenuated by a factor of about 50 over a distance of 20 cm. © 2012 Elsevier B.V. All rights reserved.

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  • Radon removal from gaseous xenon with activated charcoal

    K. Abe, K. Hieda, K. Hiraide, S. Hirano, Y. Kishimoto, K. Kobayashi, Y. Koshio, J. Liu, K. Martens, S. Moriyama, M. Nakahata, H. Nishiie, H. Ogawa, H. Sekiya, A. Shinozaki, Y. Suzuki, O. Takachio, A. Takeda, K. Ueshima, D. Umemoto, M. Yamashita, K. Hosokawa, A. Murata, K. Otsuka, Y. Takeuchi, F. Kusaba, D. Motoki, K. Nishijima, S. Tasaka, K. Fujii, I. Murayama, S. Nakamura, Y. Fukuda, Y. Itow, K. Masuda, Y. Nishitani, H. Takiya, H. Uchida, Y. D. Kim, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   661 ( 1 ) 50 - 57  2012.01

     View Summary

    Many low background experiments using xenon need to remove radioactive radon to improve their sensitivities. However, no method of continually removing radon from xenon has been described in the literature. We studied a method to remove radon from xenon gas through an activated charcoal trap. From our measurements we infer a linear relationship between the mean propagation velocity vRn of radon and vXe of xenon in the trap with vRn/vXe=(0.96±0.10)×10-3 at -85 °C. As the mechanism for radon removal in this charcoal trap is its decay, knowledge of this parameter allows us to design an efficient radon removal system for the XMASS experiment. The verification of this system found that it reduces radon by a factor of 0.07, which is in line with its expected average retention time of 14.8 days for radon. © 2011 Elsevier B.V.

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  • Scintillation-only based pulse shape discrimination for nuclear and electron recoils in liquid xenon

    K. Ueshima, K. Abe, K. Hiraide, S. Hirano, Y. Kishimoto, K. Kobayashi, Y. Koshio, J. Liu, K. Martens, S. Moriyama, M. Nakahata, H. Nishiie, H. Ogawa, H. Sekiya, A. Shinozaki, Y. Suzuki, A. Takeda, M. Yamashita, K. Fujii, I. Murayama, S. Nakamura, K. Otsuka, Y. Takeuchi, Y. Fukuda, K. Nishijima, D. Motoki, Y. Itow, K. Masuda, Y. Nishitani, H. Uchida, S. Tasaka, H. Ohsumi, Y. D. Kim, Y. H. Kim, K. B. Lee, M. K. Lee, J. S. Lee

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   659 ( 1 ) 161 - 168  2011.12

     View Summary

    In a dedicated test setup at the Kamioka Observatory we studied pulse shape discrimination (PSD) in liquid xenon (LXe) for dark matter searches in the absence of an externally applied electric field. PSD in LXe was based on the observation that scintillation light from electron events was emitted over a longer period of time than that of nuclear recoil events, and our method used a simple ratio of early to total scintillation light emission in a single scintillation event. Requiring an efficiency of 50% for nuclear recoil retention we reduced the electron background by a factor of 7.7±1.1(stat) ±0.61.2(sys)×10-2 at energies between 4.8 and 7.2 keVee and 7.7±2.8(stat)± 2.82.5(sys)×10-3 at energies between 9.6 and 12 keVee for a scintillation light yield of 20.9 photoelectrons/keVee. Further study was done by masking some of that light to reduce this yield to 4.6 photoelectrons/keVee. Under these conditions the same method results in an electron event reduction by a factor of 2.4±0.2(stat)±0.20.3(sys)×10 -1 for the lower of the energy regions above. We also observe that in contrast to nuclear recoils the fluctuations in our early to total ratio for electron events are larger than expected from statistical fluctuations. © 2011 Published by Elsevier B.V.

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  • Solar neutrino results in Super-Kamiokande-III

    K. Abe, Y. Hayato, T. Iida, M. Ikeda, C. Ishihara, K. Iyogi, J. Kameda, K. Kobayashi, Y. Koshio, Y. Kozuma, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, T. Yokozawa, S. Hazama, H. Kaji, T. Kajita, K. Kaneyuki, T. McLachlan, K. Okumura, Y. Shimizu, N. Tanimoto, M. R. Vagins, L. Labarga, L. M. Magro, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, A. Renshaw, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, J. Albert, R. Wendell, T. Wongjirad, K. Scholberg, C. W. Walter, T. Ishizuka, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, H. Nishino, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, Y. Takeuchi, A. Minamino, T. Nakaya, Y. Fukuda, Y. Itow, G. Mitsuka, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, R. Terri, C. Yanagisawa, N. Tamura, H. Ishino, A. Kibayashi, S. Mino, T. Mori

    Physical Review D - Particles, Fields, Gravitation and Cosmology   83 ( 5 )  2011.03

     View Summary

    The results of the third phase of the Super-Kamiokande solar neutrino measurement are presented and compared to the first and second phase results. With improved detector calibrations, a full detector simulation, and improved analysis methods, the systematic uncertainty on the total neutrino flux is estimated to be ±2.1%, which is about two thirds of the systematic uncertainty for the first phase of Super-Kamiokande. The observed B8 solar flux in the 5.0 to 20 MeV total electron energy region is 2.32±0.04(stat) ±0.05(sys)×106cm-2sec-1 under the assumption of pure electron-flavor content, in agreement with previous measurements. A combined oscillation analysis is carried out using SK-I, II, and III data, and the results are also combined with the results of other solar neutrino experiments. The best-fit oscillation parameters are obtained to be sin2θ12=0.30-0.01+0.02(tan2θ 12=0.42-0.02+0.04) and Δm212=6.2-1.9+1.1×10 -5eV2. Combined with KamLAND results, the best-fit oscillation parameters are found to be sin2θ12=0.31±0. 01(tan2θ12=0.44±0.03) and Δm212=7.6±0.2×10-5eV2. The B8 neutrino flux obtained from global solar neutrino experiments is 5.3±0.2(stat+sys) ×106cm-2s-1, while the B8 flux becomes 5.1±0.1(stat+sys)×106cm-2s-1 by adding KamLAND results. In a three-flavor analysis combining all solar neutrino experiments, the upper limit of sin2θ13 is 0.060 at 95% C.L.. After combination with KamLAND results, the upper limit of sin2θ13 is found to be 0.059 at 95% C.L. © 2011 American Physical Society.

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  • Measurement of inclusive π0 production in the charged-current interactions of neutrinos in a 1.3-GeV wide band beam

    C. Mariani, A. Tornero-Lopez, J. L. Alcaraz, S. Andringa, S. Aoki, Y. Aoyama, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fujii, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, Y. Hayato, R. L. Helmer, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover Manas, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, Yu Kudenko, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, S. Matsuno, V. Matveev, K. McConnel Mahn, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya, S. Nakayama, T. Namba

    Physical Review D - Particles, Fields, Gravitation and Cosmology   83 ( 5 )  2011.03

     View Summary

    In this paper, we report on the measurement of the rate of inclusive π0 production induced by charged-current neutrino interactions in a C 8H8 target at a mean energy of 1.3 GeV in the K2K near detector. Out of a sample of 11606 charged-current neutrino interactions, we select 479 π0 events with two reconstructed photons. We find that the cross section for the inclusive π0 production relative to the charged-current quasielastic cross section is σCCπ0σCCQE=0. 426±0.032(stat)±0.035(syst). The energy-dependent cross section ratio is also measured. The results are consistent with previous experiments for exclusive channels on different targets. © 2011 American Physical Society.

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  • Atmospheric neutrino oscillation analysis with subleading effects in Super-Kamiokande I, II, and III

    R. Wendell, C. Ishihara, K. Abe, Y. Hayato, T. Iida, M. Ikeda, K. Iyogi, J. Kameda, K. Kobayashi, Y. Koshio, Y. Kozuma, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, T. Yokozawa, S. Hazama, H. Kaji, T. Kajita, K. Kaneyuki, T. McLachlan, K. Okumura, Y. Shimizu, N. Tanimoto, M. R. Vagins, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, J. Albert, M. Fechner, K. Scholberg, C. W. Walter, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, H. Nishino, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. Minamino, T. Nakaya, Y. Fukuda, Y. Itow, G. Mitsuka, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, C. Yanagisawa, N. Tamura, H. Ishino, A. Kibayashi, S. Mino, T. Mori, M. Sakuda, H. Toyota, Y. Kuno, M. Yoshida, S. B. Kim

    Physical Review D - Particles, Fields, Gravitation and Cosmology   81 ( 9 )  2010.05

     View Summary

    We present a search for nonzero θ13 and deviations of sin2θ23 from 0.5 in the oscillations of atmospheric neutrino data from Super-Kamiokande I, II, and III. No distortions of the neutrino flux consistent with nonzero θ13 are found and both neutrino mass hierarchy hypotheses are in agreement with the data. The data are best fit at Δm2=2.1×10-3eV2, sin2θ13=0.0, and sin2θ23=0.5. In the normal (inverted) hierarchy θ13 and Δm2 are constrained at the one-dimensional 90% C.L. to sin2θ13<0.04(0.09) and 1.9(1.7)×10 -3<Δm2<2.6(2.7)×10-3eV2. The atmospheric mixing angle is within 0.407≤sin2θ23≤0.583 at 90% C.L. © 2010 The American Physical Society.

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  • Kinematic reconstruction of atmospheric neutrino events in a large water Cherenkov detector with proton identification

    M. Fechner, K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, S. Hazama, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, N. Tanimoto, M. R. Vagins, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, S. Dazeley, R. Svoboda, K. Bayes, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. Wendell, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. Minamino, T. Nakaya, M. Yokoyama, Y. Fukuda, Y. Itow, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, R. Terri, C. Yanagisawa, N. Tamura, Y. Idehara, M. Sakuda, Y. Kuno, M. Yoshida, S. B. Kim, B. S. Yang, T. Ishizuka, H. Okazawa, Y. Choi, H. K. Seo, Y. Furuse

    Physical Review D - Particles, Fields, Gravitation and Cosmology   79 ( 11 )  2009.06

     View Summary

    We report the development of a proton identification method for the Super-Kamiokande (SK) detector. This new tool is applied to the search for events with a single proton track, a high purity neutral current sample of interest for sterile neutrino searches. After selection using a neural network, we observe 38 events in the combined SK-I and SK-II data corresponding to 2285.1 days of exposure, with an estimated signal-to-background ratio of 1.6 to 1. Proton identification was also applied to a direct search for charged-current quasielastic (CCQE) events, obtaining a high precision sample of fully kinematically reconstructed atmospheric neutrinos, which has not been previously reported in water Cherenkov detectors. The CCQE fraction of this sample is 55%, and its neutrino (as opposed to antineutrino) fraction is 91.7±3%. We selected 78μ-like and 47 e-like events in the SK-I and SK-II data set. With this data, a clear zenith angle distortion of the neutrino direction itself is reported in a sub-GeV sample of μ neutrinos where the lepton angular correlation to the incoming neutrino is weak. Our fit to νμ→ντ oscillations using the neutrino LE distribution of the CCQE sample alone yields a wide acceptance region compatible with our previous results and excludes the no-oscillation hypothesis at 3-sigma. © 2009 The American Physical Society.

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  • First study of neutron tagging with a water Cherenkov detector

    H. Watanabe, H. Zhang, K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, S. Yamada, S. Hazama, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, N. Tanimoto, S. Clark, S. Desai, F. Dufour, E. Kearns, S. Likhoded, M. Litos, J. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, J. Dunmore, J. Griskevich, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeong, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, C. W. Walter, R. Wendel, S. Tasaka, G. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. K. Ichikawa, A. Minamino, T. Nakaya, M. Yokoyama, T. J. Haines, S. Dazeley, R. Svoboda, R. Gran, A. Habig, Y. Fukuda, Y. Itow, T. Tanaka, C. K. Jung, C. McGrew, A. Sarrat, R. Terri

    Astroparticle Physics   31 ( 4 ) 320 - 328  2009.05

     View Summary

    A first study of neutron tagging is conducted in Super-Kamiokande, a 50,000 ton water Cherenkov detector. The tagging efficiencies of thermal neutrons are evaluated in a 0.2% GdCl3-water solution and pure water. They are determined to be, respectively, 66.7% for events above 3 MeV and 20% with corresponding background probabilities of 2 × 10- 4 and 3 × 10- 2. This newly developed technique may enable water Cherenkov detectors to identify over(ν, ̄)e's from astrophysical sources as well as those produced by commercial reactors via the delayed coincidence scheme. © 2009 Elsevier B.V.

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  • Direct proton decay of the isoscalar giant dipole resonance in 208Pb

    B. K. Nayak, U. Garg, M. Koss, T. Li, E. Martis, H. Fujimura, M. Fujiwara, K. Hara, K. Kawase, K. Nakanishi, E. Obayashi, H. P. Yoshida, M. Itoh, S. Kishi, H. Sakaguchi, H. Takeda, M. Uchida, Y. Yasuda, M. Yosoi, R. G.T. Zegers, H. Akimune, M. N. Harakeh, M. Hunyadi

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   674 ( 4-5 ) 281 - 285  2009.04  [Refereed]

     View Summary

    The excitation and subsequent proton decay of the isoscalar giant dipole resonance (ISGDR) in 208Pb have been investigated via the 208Pb (α, α′ p) 207Tl reaction at 400 MeV. Excitation of the ISGDR has been identified by the difference-of-spectra method. The enhancement of the ISGDR strength at high excitation energies observed in the multipole-decomposition-analysis of the singles 208Pb (α, α′) spectra is not present in the excitation energy spectrum obtained in coincidence measurement. The partial branching ratios for direct proton decay of ISGDR to low-lying states of 207Tl have been determined and the results are compared with predictions of continuum random-phase-approximation (CRPA) calculations. © 2009 Elsevier B.V. All rights reserved.

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  • Search for proton decay via p→e+π0 and p→μ+π0 in a large water cherenkov detector

    H. Nishino, S. Clark, K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, S. Hazama, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, K. Okumura, N. Tanimoto, M. R. Vagins, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, S. Dazeley, R. Svoboda, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, C. W. Walter, R. Wendell, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. Minamino, T. Nakaya, M. Yokoyama, Y. Fukuda, Y. Itow, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, R. Terri, C. Yanagisawa, N. Tamura, Y. Idehara, M. Sakuda, Y. Kuno, M. Yoshida, S. B. Kim, B. S. Yang, T. Ishizuka, H. Okazawa, Y. Choi, H. K. Seo

    Physical Review Letters   102 ( 14 )  2009.04

     View Summary

    We have searched for proton decays via p→e+π0 and p→μ+π0 using data from a 91.7kt•yr exposure of Super-Kamiokande-I and a 49.2kt•yr exposure of Super-Kamiokande-II. No candidate events were observed with expected backgrounds induced by atmospheric neutrinos of 0.3 events for each decay mode. From these results, we set lower limits on the partial lifetime of 8.2×1033 and 6.6×1033 years at 90% confidence level for p→e+π0 and p→μ+π0 modes, respectively. © 2009 The American Physical Society.

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  • Search for neutrinos from GRB 080319B at super-kamiokande

    E. Thrane, K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, M. R. Vagins, S. Hazama, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, N. Tanimoto, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeong, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, C. W. Walter, R. Wendell, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. K. Ichikawa, A. Minamino, T. Nakaya, M. Yokoyama, S. Dazeley, R. Svoboda, A. Habig, Y. Fukuda, Y. Itow, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, C. Yanagisawa, N. Tamura, Y. Idehara, H. Ishino, A. Kibayashi, M. Sakuda, Y. Kuno, M. Yoshida, S. B. Kim, B. S. Yang, T. Ishizuka

    Astrophysical Journal   697 ( 1 ) 730 - 734  2009

     View Summary

    We perform a search for neutrinos coincident with GRB 080319B - the brightest GRB observed to date - in a 1000 s window. No statistically significant coincidences were observed and we thereby obtain an upper limit on the fluence of neutrino-induced muons from this source. From this we apply reasonable assumptions to derive a limit on neutrino fluence from the GRB. © 2009. The American Astronomical Society. All rights reserved.

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  • Search for astrophysical neutrino point sources at super-kamiokande

    E. Thrane, K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takenaga, Y. Takeuchi, K. Ueno, K. Ueshima, H. Watanabe, S. Yamada, M. R. Vagins, S. Hazama, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, N. Tanimoto, F. Dufour, E. Kearns, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, M. Goldhaber, K. Bays, D. Casper, J. P. Cravens, W. R. Kropp, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeong, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, C. W. Walter, R. Wendell, S. Tasaka, J. G. Learned, S. Matsuno, Y. Watanabe, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, K. Sakashita, T. Sekiguchi, T. Tsukamoto, A. T. Suzuki, A. K. Ichikawa, A. Minamino, T. Nakaya, M. Yokoyama, S. Dazeley, R. Svoboda, A. Habig, Y. Fukuda, Y. Itow, T. Tanaka, C. K. Jung, G. Lopez, C. McGrew, C. Yanagisawa, N. Tamura, Y. Idehara, H. Ishino, A. Kibayashi, M. Sakuda, Y. Kuno, M. Yoshida, S. B. Kim, B. S. Yang, T. Ishizuka

    Astrophysical Journal   704 ( 1 ) 503 - 512  2009

     View Summary

    It has been hypothesized that large fluxes of neutrinos may be created in astrophysical "cosmic accelerators." The primary background for a search for astrophysical neutrinos comes from atmospheric neutrinos, which do not exhibit the pointlike directional clustering that characterizes a distant astrophysical signal. We perform a search for neutrino point sources using the upward-going muon data from three phases of operation (SK-I, SK-II, and SK-III) spanning 2623 days of live time taken from 1996 April 1 to 2007 August 11. The search looks for signals from suspected galactic and extragalactic sources, transient sources, and uncataloged sources. While we find interesting signatures from two objects - RX J1713.7-3946 (97.5% CL) and GRB 991004D (95.3% CL) - these signatures lack compelling statistical significance given trial factors. We set limits on the flux and fluence of neutrino point sources above energies of 1.6 GeV. © 2009 The American Astronomical Society. All rights reserved.

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  • Measurement of single charged pion production in the charged-current interactions of neutrinos in a 1.3GeV wide band beam

    A. Rodriguez, L. Whitehead, J. L. Alcaraz, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fujii, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, Y. Hayato, R. L. Helmer, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, Yu Kudenko, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, S. Matsuno, V. Matveev, K. McConnel, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya, S. Nakayama, T. Namba

    Physical Review D - Particles, Fields, Gravitation and Cosmology   78 ( 3 )  2008.08

     View Summary

    Single charged pion production in charged-current muon neutrino interactions with carbon is studied using data collected in the K2K long-baseline neutrino experiment. The mean energy of the incident muon neutrinos is 1.3 GeV. The data used in this analysis are mainly from a fully active scintillator detector, SciBar. The cross section for single π+ production in the resonance region (W<2GeV/c2) relative to the charged-current quasielastic cross section is found to be 0.734-0.153+0.140. The energy-dependent cross section ratio is also measured. The results are consistent with a previous experiment and the prediction of our model. © 2008 The American Physical Society.

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  • Solar neutrino measurements in Super-Kamiokande-II

    J. P. Cravens, K. Abe, T. Iida, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, H. Watanabe, S. Yamada, I. Higuchi, C. Ishihara, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, F. Dufour, E. Kearns, S. Likhoded, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. Dunmore, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, N. Tanimoto, C. W. Walter, R. Wendell, R. W. Ellsworth, S. Tasaka, G. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, Y. Watanabe, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hiraide, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, G. W. Sullivan, D. Turcan, A. Habig, Y. Fukuda

    Physical Review D - Particles, Fields, Gravitation and Cosmology   78 ( 3 )  2008.08

     View Summary

    The results of the second phase of the Super-Kamiokande solar neutrino measurement are presented and compared to the first phase. The solar neutrino flux spectrum and time variation as well as oscillation results are statistically consistent with the first phase and do not show spectral distortion. The time-dependent flux measurement of the combined first and second phases coincides with the full period of solar cycle 23 and shows no correlation with solar activity. The measured B8 total flux is (2.38±0.05(stat.)-0.15+0.16(sys.))×106cm-2s-1 and the day-night difference is found to be (-6.3±4.2(stat.)±3.7(sys.))%. There is no evidence of systematic tendencies between the first and second phases. © 2008 The American Physical Society.

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  • Search for matter-dependent atmospheric neutrino oscillations in Super-Kamiokande

    K. Abe, Y. Hayato, T. Iida, M. Ikeda, J. Kameda, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, H. Watanabe, S. Yamada, I. Higuchi, C. Ishihara, T. Kajita, K. Kaneyuki, G. Mitsuka, H. Nishino, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, F. Dufour, E. Kearns, S. Likhoded, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, J. Dunmore, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, B. Hartfield, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeong, J. Y. Kim, I. T. Lim, K. Scholberg, M. Fechner, N. Tanimoto, C. W. Walter, R. Wendell, S. Tasaka, G. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, T. Hasegawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nishikawa, Y. Oyama, Y. Totsuka, A. T. Suzuki, T. Nakaya, H. Tanaka, M. Yokoyama, T. J. Haines, S. Dazeley, R. Svoboda, A. Habig, Y. Fukuda, T. Sato, Y. Itow, T. Koike, T. Tanaka, C. K. Jung, T. Kato, K. Kobayashi, C. McGrew, A. Sarrat, R. Terri, C. Yanagisawa, N. Tamura, Y. Idehara

    Physical Review D - Particles, Fields, Gravitation and Cosmology   77 ( 5 )  2008.03

     View Summary

    We consider νμ→ντ oscillations in the context of the mass varying neutrino (MaVaN) model, where the neutrino mass can vary depending on the electron density along the flight path of the neutrino. Our analysis assumes a mechanism with dependence only upon the electron density, hence ordinary matter density, of the medium through which the neutrino travels. Fully-contained, partially-contained and upward-going muon atmospheric neutrino data from the Super-Kamiokande detector, taken from the entire SK-I period of 1489 live days, are compared to MaVaN model predictions. We find that, for the case of 2-flavor oscillations, and for the specific models tested, oscillation independent of electron density is favored over density dependence. Assuming maximal mixing, the best-fit case and the density-independent case do not differ significantly. © 2008 The American Physical Society.

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  • Experimental study of the atmospheric neutrino backgrounds for p→e+π0 searches in water Cherenkov detectors

    S. Mine, J. L. Alcaraz, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fujii, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, Y. Hayato, R. L. Helmer, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, Yu Kudenko, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, S. Matsuno, V. Matveev, K. McConnel, C. McGrew, S. Mikheyev, A. Minamino, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya, S. Nakayama, T. Namba, R. Nambu, S. Nawang

    Physical Review D - Particles, Fields, Gravitation and Cosmology   77 ( 3 )  2008.02

     View Summary

    The atmospheric neutrino background for proton decay via p→e+π0 in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, 3.14×105 neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1000 ton water Cherenkov detector (KT). The KT charged-current single π0 production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained p→e+π0 background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is 1.63-0.33+0.42(stat)-0.51+0.45(syst)(megaton-year)- 1. This result is also relevant to possible future, megaton-scale water Cherenkov detectors. © 2008 The American Physical Society.

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  • Study of TeV neutrinos with upward showering muons in Super-Kamiokande

    S. Desai, K. Abe, Y. Hayato, K. Iida, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, Y. Obayashi, H. Ogawa, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, H. Watanabe, S. Yamada, I. Higuchi, C. Ishihara, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, K. Okumura, C. Saji, Y. Takenaga, S. T. Clark, F. Dufour, E. Kearns, S. Likhoded, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, J. Dunmore, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, B. Hartfiel, J. Hill, W. E. Keig, J. S. Jang, I. S. Jeong, J. Y. Kim, I. T. Lim, M. Fechner, K. Scholberg, N. Tanimoto, C. W. Walter, R. Wendell, S. Tasaka, G. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, A. K. Ichikawa, T. Ishida, T. Ishii, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hiraide, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, M. Swanson, A. Clough, R. Gran, A. Habig, Y. Fukuda, T. Sato, Y. Itow

    Astroparticle Physics   29 ( 1 ) 42 - 54  2008.02

     View Summary

    A subset of neutrino-induced upward through-going muons in the Super-Kamiokande detector consists of high-energy muons which lose energy through radiative processes such as bremsstrahlung, e+ e- pair production and photonuclear interactions. These "upward showering muons" comprise an event sample whose mean parent neutrino energy is approximately 1 TeV. We show that the zenith angle distribution of upward showering muons is consistent with negligible distortion due to neutrino oscillations, as expected of such a high-energy neutrino sample. We present astronomical searches using these high-energy events, such as those from WIMP annihilations in the Sun, Earth and Galactic Center, some suspected point sources, as well as searches for diffuse flux from the interstellar medium. © 2007 Elsevier B.V. All rights reserved.

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  • Observation of the anisotropy of 10 TeV primary cosmic ray nuclei flux with the Super-Kamiokande-I detector

    G. Guillian, J. Hosaka, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, Y. Obayashi, H. Ogawa, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, S. Yamada, I. Higuchi, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, A. Okada, K. Okumura, C. Saji, Y. Takenaga, S. Desai, E. Kearns, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, W. Gajewski, J. Griskevich, W. R. Kropp, D. W. Liu, S. Mine, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, K. Scholberg, C. W. Walter, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, A. Habig, Y. Fukuda, Y. Itow, M. Sakuda, M. Yoshida, S. B. Kim, J. Yoo, H. Okazawa, T. Ishizuka, C. K. Jung, T. Kato, K. Kobayashi, M. Malek, C. Mauger, C. McGrew, E. Sharkey, C. Yanagisawa

    Physical Review D - Particles, Fields, Gravitation and Cosmology   75 ( 6 )  2007.03

     View Summary

    The relative sidereal variation in the arrival direction of primary cosmic ray nuclei of median energy 10 TeV was measured using downward, through-going muons detected with the Super-Kamiokande-I detector. The projection of the anisotropy map onto the right ascension axis has a first harmonic amplitude of (6.64±0.98stat±0.55syst)×10-4 and a phase at maximum at (33.2°±8.2°stat±5.1°syst) right ascension. A sky map in equatorial coordinates indicates an excess region in the constellation of Taurus and a deficit region toward Virgo. The excess region is centered at (αT,δT)=(75°±7°,-5°±9°) with a half-opening angle χT=(39±7)°; the excess flux is (0.104±0.020)% above the isotropic expectation. The corresponding parameters for the deficit region are (αV,δV)= (205°±7°,5°±10°), χV=(54±7)°, and (-0.094±0.014)%. The data do not allow us to rule out a pure dipole form for the anisotropy (allowed at 13% confidence level); they are better described by the excess and deficit cones described above. We explored the implications under the assumption that the true anisotropy is not distorted too much by the analysis filter so that it is well-described by the observed excess and deficit cones. © 2007 The American Physical Society.

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  • Energy spectrum and arrival directions of high-energy electrons over 100 GeV observed with PPB-BETS

    K. Yoshida, S. Torii, T. Tamura, H. Kitamura, T. Yamagami, J. Chang, I. Iijima, A. Kadokura, K. Kasahara, Y. Katayose, T. Kobayashi, Y. Komori, Y. Matsuzaka, K. Mizutani, H. Murakami, M. Namiki, J. Nishimura, S. Ohta, Y. Saito, M. Shibata, N. Tateyama, H. Yamagishi, T. Yuda

    Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007   2 ( OG PART 1 ) 59 - 62  2007  [Refereed]

     View Summary

    We have observed cosmic-ray electrons from 10 GeV to 1 TeV with PPB-BETS by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. The geometrical factor of detector is about 600 cm2sr and the total thickness of lead absorber is 9 radiation lengths. We have collected 5.7103 events over 100 GeV including nearly 100 candidates of primary electrons. During the flight, sun aspect sensors and geomagnetic aspect sensors operated to determine the attitude of the instrument. The arrival directions of high-energy electrons over 100 GeV, together with the energy spectrum, are suggested to be a powerful probe to identify nearby cosmic- ray electron sources. In this paper, we present the energy spectrum and arrival directions of cosmic-ray electrons from 100 GeV to 1 TeV observed with PPB-BETS.

  • Study of the pionic enhancement in O-16(p, p ')O-16(0(-) ,T=1) at 295 MeV

    T Wakasa, GPA Berg, H Fujimura, K Fujita, K Hatanaka, M Ichimura, M Itoh, J Kamiya, T Kawabata, Y Kitamura, E Obayashi, H Sakaguchi, N Sakamoto, Y Sakemi, Y Shimizu, H Takeda, A Uchida, Y Yasuda, HP Yoshida, A Yosoi

    PHYSICS LETTERS B   632 ( 4 ) 485 - 489  2006.01  [Refereed]

     View Summary

    The cross section of the O-16(p, p') O-16(0(-), T = 1) scattering was measured at a bombarding energy of 295 MeV in the momentum transfer range of 1.0 fm(-1) &lt;= q(c.m.). &lt; 2.1 fm(-1). The isovector 0(-) state at E-x = 12.8 MeV is clearly separated from its neighboring states owing to the high energy resolution of about 30 keV. The cross section data were compared with distorted wave impulse approximation (DWIA) calculations employing shell-model wave functions. The observed cross sections around q(c.m.) similar or equal to 1.7 fm(-1) are significantly larger than obtained by these calculations, suggesting pionic enhancement as a precursor of pion condensation in nuclei. The data are well reproduced by DWIA calculations C C using random phase approximation response functions including the Delta isobar that predict pionic enhancement. (c) 2005 Elsevier B.V. All rights reserved.

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  • Measurement of atmospheric neutrino flux consistent with tau neutrino appearance

    K. Abe, Y. Hayato, T. Iida, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, Y. Obayashi, H. Ogawa, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, I. Higuchi, C. Ishihara, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, K. Okumura, C. Saji, Y. Takenaga, Y. Totsuka, S. Clark, S. Desai, F. Dufour, E. Kearns, S. Likhoded, M. Litos, J. L. Raaf, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, J. E. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, N. Tanimoto, C. W. Walter, R. Wendell, R. W. Ellsworth, S. Tasaka, E. Guillian, J. G. Learned, S. Matsuno, M. D. Messier, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, A. T. Suzuki, M. Hasegawa, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, G. W. Sullivan, A. Habig, R. Gran, Y. Fukuda, T. Sato, Y. Itow, T. Koike, C. K. Jung, T. Kato, K. Kobayashi, M. Malek

    Physical Review Letters   97 ( 17 )  2006

     View Summary

    A search for the appearance of tau neutrinos from νμ↔ντ oscillations in the atmospheric neutrinos has been performed using 1489.2 days of atmospheric neutrino data from the Super-Kamiokande-I experiment. A best fit tau neutrino appearance signal of 138±48(stat)-32+15(syst) events is obtained with an expectation of 78±26(syst). The hypothesis of no tau neutrino appearance is disfavored by 2.4 sigma. © 2006 The American Physical Society.

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  • Current status of solar neutrinos at super-kamiokande

    Parker Cravens, J. Hosaka, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, G. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, Y. Obayashi, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, S. Yamada, I. Higuchi, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, A. Okada, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. E. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. Wendell, R. W. Ellsworth, S. Tasaka, E. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayasln, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, J. Cooley, A. Habig, Y. Fukuda, T. Sato, Y. Itow, C. K. Jung, T. Kato, K. Kobayashi, M. Malek

    Annual Meeting of the Division of Particles and Fields of the American Physical Society, DPF 2006, and the Annual Fall Meeting of the Japan Particle Physics Community    2006

     View Summary

    • SK-III has been started and is taking data • SK-II data has been updated to its final 791d • Oscillation analysis with SK-I, SK-II data has been performed and shows consistency with final SK-I data set • SK-II shows consistency within the global analysis • Hope to see energy spectrum distortion in SK-III.

  • Improved search for Ivμ→ve oscillation in a long-baseline accelerator experiment

    S. Yamamoto, J. Zalipska, E. Aliu, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, R. L. Helmer, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Inagaki, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, D. Kerr, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, J. Kubota, Y. Kudenko, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, S. Matsuno, V. Matveev, K. McConnel, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, T. Morita, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura

    Physical Review Letters   96 ( 18 )  2006

     View Summary

    We performed an improved search for a†'Îe oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2ã-1019 protons on target. No evidence for a îe appearance signal was found, and we set bounds on the îa†Îe oscillation parameters. At Î"m2=2.8ã- 10-3eV2, the best-fit value of the K2K îÎdisappearance analysis, we set an upper limit of sina¡22iîe<0.13 at a 90% confidence level. © 2006 The American Physical Society.

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  • Solar neutrino measurements in Super-Kamiokande-I

    J. Hosaka, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, Y. Obayashi, N. Sakurai, A. Sarrat, M. Shiozawa, Y. Suzuki, Y. Takeuchi, S. Yamada, I. Higuchi, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, A. Okada, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. R. Kropp, D. W. Liu, S. Mine, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. W. Ellsworth, S. Tasaka, G. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, B. K. Kim, K. B. Lee, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, J. Cooley, A. Habig, Y. Fukuda, T. Sato, Y. Itow, C. K. Jung, T. Kato, K. Kobayashi, M. Malek

    Physical Review D - Particles, Fields, Gravitation and Cosmology   73 ( 11 )  2006

     View Summary

    The details of Super-Kamiokande-I's solar neutrino analysis are given. Solar neutrino measurement in Super-Kamiokande is a high statistics collection of B8 solar neutrinos via neutrino-electron scattering. The analysis method and results of the 1496 day data sample are presented. The final oscillation results for the data are presented also. © 2006 The American Physical Society.

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  • Three flavor neutrino oscillation analysis of atmospheric neutrinos in Super-Kamiokande

    J. Hosaka, K. Ishihara, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, Y. Obayashi, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, S. Yamada, I. Higuchi, M. Ishitsuka, T. Kajita, K. Kaneyuki, G. Mitsuka, S. Nakayama, H. Nishino, A. Okada, K. Okumura, C. Saji, Y. Takenaga, S. Clark, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. R. Kropp, D. W. Liu, S. Mine, C. Regis, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. E. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. Wendell, R. W. Ellsworth, S. Tasaka, E. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Nakadaira, K. Nakamura, K. Nitta, Y. Oyama, Y. Totsuka, A. T. Suzuki, M. Hasegawa, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, T. Sasaki, H. Sato, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, J. Cooley, A. Habig, Y. Fukuda, T. Sato, Y. Itow, C. K. Jung, T. Kato, K. Kobayashi, M. Malek, C. Mauger

    Physical Review D - Particles, Fields, Gravitation and Cosmology   74 ( 3 )  2006

     View Summary

    We report on the results of a three-flavor oscillation analysis using Super-Kamiokande I atmospheric neutrino data, with the assumption of one mass scale dominance (Δm122=0). No significant flux change due to matter effect, which occurs when neutrinos propagate inside the Earth for θ13≠0, has been seen either in a multi-GeV νe-rich sample or in a νμ-rich sample. Both normal and inverted mass hierarchy hypotheses are tested and both are consistent with observation. Using Super-Kamiokande data only, 2-dimensional 90% confidence allowed regions are obtained: mixing angles are constrained to sin 2θ13<0.14 and 0.37<sin 2θ23<0.65 for the normal mass hierarchy. Weaker constraints, sin 2θ13<0.27 and 0.37<sin 2θ23<0.69, are obtained for the inverted mass hierarchy case. © 2006 The American Physical Society.

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  • Measurement of the quasielastic axial vector mass in neutrino interactions on oxygen

    R. Gran, E. J. Jeon, E. Aliu, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fukuda, J. Gomez-Cadenas, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, R. L. Helmer, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Inagaki, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, D. Kerr, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, J. Kubota, Yu Kudenko, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, S. Matsuno, V. Matveev, K. B. McConnel Mahn, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, T. Morita, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya

    Physical Review D - Particles, Fields, Gravitation and Cosmology   74 ( 5 )  2006

     View Summary

    The weak nucleon axial-vector form factor for quasielastic interactions is determined using neutrino interaction data from the K2K Scintillating Fiber detector in the neutrino beam at KEK. More than 12000 events are analyzed, of which half are charged-current quasielastic interactions νμn→μ-p occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for oxygen and assume the form factor is approximately a dipole with one parameter, the axial-vector mass MA, and fit to the shape of the distribution of the square of the momentum transfer from the nucleon to the nucleus. Our best fit result for MA=1.20±0.12GeV. Furthermore, this analysis includes updated vector form factors from recent electron scattering experiments and a discussion of the effects of the nucleon momentum on the shape of the fitted distributions. © 2006 The American Physical Society.

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  • Measurement of neutrino oscillation by the K2K experiment

    M. H. Ahn, E. Aliu, S. Andringa, S. Aoki, Y. Aoyama, J. Argyriades, K. Asakura, R. Ashie, F. Berghaus, H. G. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, S. C. Boyd, J. Burguet-Castell, D. Casper, J. Catala, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, S. Echigo, X. Espinal, M. Fechner, E. Fernandez, K. Fujii, Y. Fujii, S. Fukuda, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, R. L. Helmer, I. Higuchi, J. Hill, K. Hiraide, E. Hirose, J. Hosaka, A. K. Ichikawa, M. Ieiri, M. Iinuma, A. Ikeda, T. Inagaki, T. Ishida, K. Ishihara, H. Ishii, T. Ishii, H. Ishino, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, J. S. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, B. H. Kang, I. Kato, Y. Kato, E. Kearns, D. Kerr, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, B. J. Kim, H. I. Kim, J. H. Kim, J. Y. Kim, S. B. Kim, M. Kitamura, P. Kitching, K. Kobayashi, T. Kobayashi, M. Kohama, A. Konaka, Y. Koshio, W. Kropp, J. Kubota, Yu Kudenko, G. Kume, Y. Kuno, Y. Kurimoto, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, S. H. Lim

    Physical Review D - Particles, Fields, Gravitation and Cosmology   74 ( 7 )  2006

     View Summary

    We present measurements of νμ disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One-hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of 158.1-8.6+9.2 events without oscillation. A distortion of the energy spectrum is also seen in 58 single-ring muonlike events with reconstructed energies. The probability that the observations are explained by the expectation for no neutrino oscillation is 0.0015% (4.3σ). In a two-flavor oscillation scenario, the allowed Δm2 region at sin 22θ=1 is between 1.9 and 3.5×10-3eV2 at the 90% C.L. with a best-fit value of 2.8×10-3eV2. © 2006 The American Physical Society.

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    719
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  • Search for coherent charged pion production in neutrino-carbon interactions

    M. Hasegawa, E. Aliu, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, C. Cavata, A. Cervera, S. M. Chen, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, T. Hasegawa, K. Hayashi, Y. Hayato, R. L. Helmer, J. Hill, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Inagaki, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, D. Kerr, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. B. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, J. Kubota, Y. Kudenko, Y. Kuno, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, T. Maruyama, S. Matsuno, V. Matveev, C. Mauger, K. McConnel, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, T. Morita, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya

    Physical Review Letters   95 ( 25 )  2005.12

     View Summary

    We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of 0.60×10-2 is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV. © 2005 The American Physical Society.

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  • Design, construction, and initial performance of SciBar detector in K2K experiment

    S. Yamamoto, S. Andringa, S. Aoki, S. Choi, U. Dore, X. Espinal, J. J. Gomez-Cadenas, R. Gran, M. Hasegawa, K. Hayashi, K. Hayashi, Y. Hayato, K. Hiraide, A. K. Ichikawa, M. Iinuma, J. S. Jang, E. J. Jeon, K. K. Joo, G. Jover-Mañas, C. K. Jung, I. Kato, D. Kerr, J. Y. Kim, S. B. Kim, K. Kobayashi, A. Kohara, J. Kubota, Yu Kudenko, Y. Kuno, M. J. Lee, E. Lessac-Chenin, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, C. Mariani, C. McGrew, O. Mineev, T. Morita, T. Murakami, Y. Nakanishi, T. Nakaya, S. Nawang, K. Nishikawa, K. Nitta, F. Nova, M. Y. Pac, E. J. Rhee, A. Rodriguez, F. Sanchez, T. Sasaki, K. K. Shiraishi, A. Suzuki, T. Takahashi, Y. Takubo, M. Tanaka, R. Terri, A. Tornero-Lopez, S. Ueda, L. Whitehead, R. J. Wilkes, M. Yokoyama, M. Yoshida

    IEEE Transactions on Nuclear Science   52 ( 6 ) 2992 - 2997  2005.12

     View Summary

    A new near detector for the K2K long baseline neutrino experiment, the SciBar, was constructed and started data taking to study neutrino interactions. In K2K, neutrino oscillation is studied by comparing the number of neutrino interactions and energy spectrum between near and far detectors. In order to study neutrino oscillations more precisely, it is necessary to improve the measurement of neutrino spectrum and interactions below 1 GeV, where the latest K2K results suggest maximum oscillation. For that purpose, SciBar is designed to be fully active with fine segmentation. We present the design and basic performance. All detector components have been working as expected. Also presented are the measurements of charged current interactions which are used in the latest K2K oscillation analysis. © 2005 IEEE.

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    10
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  • Search for nucleon decay via modes favored by supersymmetric grand unification models in Super-Kamiokande-I

    K. Kobayashi, M. Earl, Y. Ashie, J. Hosaka, K. Ishihara, Y. Itow, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, M. Shiozawa, Y. Suzuki, Y. Takeuchi, K. Taki, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, K. Okumura, T. Ooyabu, C. Saji, Y. Takenaga, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. Gajewski, W. R. Kropp, D. W. Liu, S. Mine, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. E. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. W. Ellsworth, S. Tasaka, G. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hayashi, I. Kato, H. Maesaka, T. Morita, T. Nakadaira, T. Nakaya, K. Nishikawa, T. Sasaki, S. Ueda, S. Yamamoto, M. Yokoyama, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, A. Habig, Y. Fukuda, C. K. Jung, T. Kato

    Physical Review D - Particles, Fields, Gravitation and Cosmology   72 ( 5 )  2005.09

     View Summary

    We report the results for nucleon decay searches via modes favored by supersymmetric grand unified models in Super-Kamiokande. Using 1489 days of full Super-Kamiokande-I data, we searched for p→ν̄K+, n→ν̄K0, p→μ+K0, and p→e+K0 modes. We found no evidence for nucleon decay in any of these modes. We set lower limits of partial nucleon lifetime 2.3×1033, 1.3×1032, 1.3×1033, and 1.0×1033years at 90% confidence level for p→ν̄K+, n→ν̄K0, p→μ+K0, and p→e+K0 modes, respectively. These results give a strong constraint on supersymmetric grand unification models. © 2005 The American Physical Society.

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    115
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  • Measurement of single π0 production in neutral current neutrino interactions with water by a 1.3 GeV wide band muon neutrino beam

    S. Nakayama, C. Mauger, M. H. Ahn, S. Aoki, Y. Ashie, H. Bhang, S. Boyd, D. Casper, J. H. Choi, S. Fukuda, Y. Fukuda, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, J. Hill, A. K. Ichikawa, A. Ikeda, T. Inagaki, T. Ishida, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, J. S. Jang, E. J. Jeon, K. K. Joo, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, A. Kibayashi, D. Kielczewska, B. J. Kim, C. O. Kim, J. Y. Kim, S. B. Kim, K. Kobayashi, T. Kobayashi, Y. Koshio, W. R. Kropp, J. G. Learned, S. H. Lim, I. T. Lim, H. Maesaka, T. Maruyama, S. Matsuno, C. McGrew, A. Minamino, S. Mine, M. Miura, K. Miyano, T. Morita, S. Moriyama, M. Nakahata, K. Nakamura, I. Nakano, F. Nakata, T. Nakaya, T. Namba, R. Nambu, K. Nishikawa, S. Nishiyama, K. Nitta, S. Noda, Y. Obayashi, A. Okada, Y. Oyama, M. Y. Pac, H. Park, C. Saji, M. Sakuda, A. Sarrat, T. Sasaki, N. Sasao, K. Scholberg, M. Sekiguchi, E. Sharkey, M. Shiozawa, K. K. Shiraishi, M. Smy, H. W. Sobel, J. L. Stone, Y. Suga, L. R. Sulak, A. Suzuki, Y. Suzuki, Y. Takeuchi, N. Tamura, M. Tanaka, Y. Totsuka, S. Ueda, M. R. Vagins, C. W. Walter, W. Wang

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   619 ( 3-4 ) 255 - 262  2005.07

     View Summary

    Neutral current single π0 production induced by neutrinos with a mean energy of 1.3 GeV is measured using a 1000 ton water Cherenkov detector in the K2K long baseline neutrino experiment. The cross section for this process relative to the total charged current cross section is measured to be 0.064±0.001(stat.)±0.007(sys.). The momentum distribution of neutral current π0s from a water target is measured with high statistics for the first time. © 2005 Elsevier B.V. All rights reserved.

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    74
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  • Measurement of atmospheric neutrino oscillation parameters by Super-Kamiokande I

    Y. Ashie, J. Hosaka, K. Ishihara, Y. Itow, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, M. Shiozawa, Y. Suzuki, Y. Takeuchi, K. Taki, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, K. Okumura, C. Saji, Y. Takenaga, S. T. Clark, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. Gajewski, W. R. Kropp, D. W. Liu, S. Mine, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, K. Scholberg, C. W. Walter, R. W. Ellsworth, S. Tasaka, G. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hayashi, I. Kato, H. Maesaka, T. Morita, T. Nakaya, K. Nishikawa, T. Sasaki, S. Ueda, S. Yamamoto, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, A. Habig, Y. Fukuda, C. K. Jung, T. Kato, K. Kobayashi, M. Malek, C. Mauger, C. McGrew

    Physical Review D - Particles, Fields, Gravitation and Cosmology   71 ( 11 )  2005.06

     View Summary

    We present a combined analysis of fully-contained, partially-contained and upward-going muon atmospheric neutrino data from a 1489d exposure of the Super-Kamiokande detector. The data samples span roughly five decades in neutrino energy, from 100MeV to 10eV. A detailed Monte Carlo comparison is described and presented. The data is fit to the Monte Carlo expectation, and is found to be consistent with neutrino oscillations of νμντ with sin22θ>0.92 and 1.5×10-3<Δm2<3.4×10-3eV2 at 90% confidence level. © 2005 The American Physical Society.

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  • Evidence for muon neutrino oscillation in an accelerator-based experiment

    E. Aliu, S. Andringa, S. Aoki, J. Argyriades, K. Asakura, R. Ashie, H. Berns, H. Bhang, A. Blondel, S. Borghi, J. Bouchez, J. Burguet-Castell, D. Casper, C. Cavata, A. Cervera, K. O. Cho, J. H. Choi, U. Dore, X. Espinal, M. Fechner, E. Fernandez, Y. Fukuda, J. Gomez-Cadenas, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, R. L. Helmer, J. Hill, K. Hiraide, J. Hosaka, A. K. Ichikawa, M. Iinuma, A. Ikeda, T. Inagaki, T. Ishida, K. Ishihara, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, E. J. Jeon, I. S. Jeong, K. Joo, G. Jover, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, D. Kerr, C. O. Kim, M. Khabibullin, A. Khotjantsev, D. Kielczewska, J. Y. Kim, S. Kim, P. Kitching, K. Kobayashi, T. Kobayashi, A. Konaka, Y. Koshio, W. Kropp, J. Kubota, Y. Kudenko, Y. Kuno, T. Kutter, J. Learned, S. Likhoded, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, J. Mallet, C. Mariani, T. Maruyama, S. Matsuno, V. Matveev, C. Mauger, K. McConnel, C. McGrew, S. Mikheyev, A. Minamino, S. Mine, O. Mineev, C. Mitsuda, M. Miura, Y. Moriguchi, T. Morita, S. Moriyama, T. Nakadaira, M. Nakahata, K. Nakamura, I. Nakano, T. Nakaya, S. Nakayama

    Physical Review Letters   94 ( 8 )  2005.03

     View Summary

    We present results for νμ oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced νμ beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of vmu;, which we presume have oscillated to ντ. The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0σ). © 2005 The American Physical Society.

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    417
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  • Detection of nuclear de-excitation gamma-rays in water Cherenkov detector

    K. Kobayashi, Y. Itow, M. Shiozawa, M. Yosoi, H. Toyokawa, H. Akimune, H. Ejiri, H. Fujimura, M. Fujiwara, K. Hara, K. Y. Hara, T. Ishikawa, M. Itoh, T. Kawabata, M. Nakamura, H. Sakaguchi, Y. Sakemi, H. Takeda, M. Uchida, T. Yamada, Y. Yasuda, H. P. Yoshida, R. G.T. Zegers

    Nuclear Physics B - Proceedings Supplements   139 ( 1-3 SPEC. ISS. ) 72 - 76  2005.02

     View Summary

    We measured de-excitation gamma-rays from 15N* s-hole state via the 16O(p,2p)15N reaction. The emission probabilities for more than 6 MeV and 3-6 MeV gamma-rays are estimated to be 3% and 5% respectively. This result is useful for tagging nucleon decay via p → ν̄K+ in Super-Kamiokande and neutrino neutral current interaction study. © 2004 Elsevier B.V. All rights reserved.

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    5
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  • The K2K SciBar detector

    K. Nitta, E. Aliu, S. Andringa, S. Aoki, S. Choi, U. Dore, X. Espinal, J. J. Gomez-Cadenas, R. Gran, M. Hasegawa, K. Hayashi, K. Hayashi, Y. Hayato, K. Hiraide, A. K. Ichikawa, M. Iinuma, J. S. Jang, E. J. Jeon, K. K. Joo, C. K. Jung, I. Kato, D. Kerr, J. Y. Kim, S. B. Kim, K. Kobayashi, A. Kohara, J. Kubota, Yu Kudenko, Y. Kuno, M. J. Lee, E. Lessac-Chenin, I. T. Lim, P. F. Loverre, L. Ludovici, H. Maesaka, C. Mariani, C. McGrew, O. Mineev, T. Morita, T. Murakami, Y. Nakanishi, T. Nakaya, S. Nawang, K. Nishikawa, M. Y. Pac, E. J. Rhee, A. Rodríguez, F. Sanchez, T. Sasaki, K. K. Shiraishi, A. Suzuki, T. Takahashi, Y. Takubo, M. Tanaka, R. Terri, A. Tornero-Lopez, S. Ueda, R. J. Wilkes, S. Yamamoto, M. Yokoyama, M. Yoshida

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   535 ( 1-2 ) 147 - 151  2004.12

     View Summary

    A new near detector, Scintillator Bar (SciBar), for the K2K long-baseline neutrino oscillation experiment was installed to improve the measurement of the neutrino energy spectrum and to study neutrino interactions in the energy region around 1 GeV. SciBar is a 'fully active' tracking detector with fine segmentation consisting of plastic scintillator bars. The detector was constructed in the summer of 2003 and is taking data since October 2003. The basic design and initial performance are presented. © 2004 Published by Elsevier B.V.

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    78
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  • Structures and decay of deep-hole states in light nuclei populated by the (p, 2p) reactions

    M. Yosoi, H. Akimune, I. Daito, H. Ejiri, H. Fujimura, M. Fujiwara, K. Hara, K. Y. Hara, T. Ishikawa, M. Itoh, Y. Itow, T. Kawabata, K. Kobayashi, M. Nakamura, T. Noro, E. Obayashi, H. Sakaguchi, Y. Sakemi, M. Shiozawa, H. Takeda, T. Taki, A. Tamii, H. Toyokawa, N. Tsukahara, M. Uchida, T. Yamada, Y. Yasuda, H. P. Yoshida, R. G.T. Zegers

    Physics of Atomic Nuclei   67 ( 10 ) 1810 - 1817  2004.10

     View Summary

    Decay particles from the s-hole states in 11B and 15N have been measured in coincidence with the quasifree 12C(p, 2p) and 16O(p, 2p) reactions at Ep = 392 MeV. Triton decay is found to be dominant for the 11B(s-hole) state and also found to be larger than α decay for the 15N(s-hole) state despite its smaller Q value compared to α decay. Measured decay branching ratios are discussed in comparison with the results of statistical-model, SU(3)-model, and shell-model calculations. The energy spectra around the s-hole states in both 11B and 15N exhibit some bumplike structures, which can be qualitatively explained by recent shell-model calculations for both nuclei. © 2004 MAIK "Nauka/Interperiodica".

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    2
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  • Evidence for an oscillatory signature in atmospheric neutrino oscillations

    Y. Ashie, J. Hosaka, K. Ishihara, Y. Itow, J. Kameda, Y. Koshio, A. Minamino, C. Mitsuda, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, M. Shiozawa, Y. Suzuki, Y. Takeuchi, K. Taki, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, K. Okumura, T. Ooyabu, C. Saji, Y. Takenaga, S. Desai, E. Kearns, S. Likhoded, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, M. Goldhaber, D. Casper, J. P. Cravens, W. Gajewski, W. R. Kropp, D. W. Liu, S. Mine, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. S. Jang, J. Y. Kim, I. T. Lim, R. W. Ellsworth, S. Tasaka, G. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hayashi, T. Inagaki, I. Kato, H. Maesaka, T. Morita, T. Nakaya, K. Nishikawa, T. Sasaki, S. Ueda, S. Yamamoto, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, Y. Fukuda, C. K. Jung, T. Kato, K. Kobayashi, M. Malek, C. Mauger

    Physical Review Letters   93 ( 10 )  2004.09

     View Summary

    The survival probability of muon neutrinos was analyzed as a function of L/E using atmospheric neutrino events observed in Super-Kamiokande. Alternative models that could explain the zenith angle and energy dependent deficit of the atmospheric muon neutrinos were disfavored. The neutrino energy was estimated from the total energy of charged particles observed in the inner detector (ID). It was concluded that the observed L/E distribution gives the first direct evidence that the neutrino survival probability obeys the sinusoidal function as predicted by neutrino flavor oscillations.

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    670
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  • Search for electron neutrino appearance in a 250 km long-baseline experiment

    M. H. Ahn, S. Aoki, Y. Ashie, H. Bhang, S. Boyd, D. Casper, J. H. Choi, S. Fukuda, Y. Fukuda, R. Gran, T. Hara, M. Hasegawa, T. Hasegawa, K. Hayashi, Y. Hayato, J. Hill, A. K. Ichikawa, A. Ikeda, T. Inagaki, T. Ishida, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, J. S. Jang, E. J. Jeon, K. K. Joo, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, A. Kibayashi, D. Kielczewska, B. J. Kim, C. O. Kim, J. Y. Kim, S. B. Kim, K. Kobayashi, T. Kobayashi, Y. Koshio, W. R. Kropp, J. G. Learned, S. H. Lim, I. T. Lim, H. Maesaka, T. Maruyama, S. Matsuno, C. Mauger, C. Mcgrew, A. Minamino, S. Mine, M. Miura, K. Miyano, T. Morita, S. Moriyama, M. Nakahata, K. Nakamura, I. Nakano, F. Nakata, T. Nakaya, S. Nakayama, T. Namba, R. Nambu, K. Nishikawa, S. Nishiyama, S. Noda, Y. Obayashi, A. Okada, Y. Oyama, M. Y. Pac, H. Park, C. Saji, M. Sakuda, A. Sarrat, T. Sasaki, N. Sasao, K. Scholberg, M. Sekiguchi, E. Sharkey, M. Shiozawa, K. K. Shiraishi, M. Smy, H. W. Sobel, J. L. Stone, Y. Suga, L. R. Sulak, A. Suzuki, Y. Suzuki, Y. Takeuchi, N. Tamura, M. Tanaka, Y. Totsuka, S. Ueda, M. R. Vagins, C. W. Walter, W. Wang, R. J. Wilkes

    Physical Review Letters   93 ( 5 )  2004.07

     View Summary

    The search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K 250 km long-baseline neutrino experiment was described. It was observed that one electron event was found in the data corresponding to an exposure of 4.8 × 1019 protons on target. The number of expected background neutrino events in the absence of neutrino oscillations was found to be 2.4±0.6 events and was found to be dominated by misidentification of events from neutral current production. The probability density function of the expected number of electron events was evaluated from the the Poisson distribution, which was convoluted with systematic uncertainty.

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  • Limits on the neutrino magnetic moment using 1496 days of Super-Kamiokande-I solar neutrino data

    D. W. Liu, Y. Ashie, S. Fukuda, Y. Fukuda, K. Ishihara, Y. Itow, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, T. Ooyabu, C. Saji, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, T. Barszczak, D. Casper, J. P. Cravens, W. Gajewski, W. R. Kropp, S. Mine, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. Y. Kim, I. T. Lim, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, J. Kameda, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hayashi, T. Inagaki, I. Kato, H. Maesaka, T. Morita, T. Nakaya, K. Nishikawa, T. Sasaki, S. Ueda, S. Yamamoto, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, C. K. Jung, T. Kato, K. Kobayashi, K. Martens, M. Malek, C. Mauger, C. McGrew

    Physical Review Letters   93 ( 2 )  2004.07

     View Summary

    A study on neutrino magnetic movement was presented using solar neutrino data obtained from Super Kamiokandel (SK). The distortions to the energy spectrum of recoil electrons from magnetic scattering by nonzero neutrino magnetic movement were also studied. The systematic uncertainty of the reconstructed energy of electrons between 5 and 20 MeV was found to be less than 0.64%. The limits on the neutrino magnetic moment were also obtained by analyzing the SK day-night energy spectra.

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  • Cluster fragmentations of deep(1s)-hole states in light nuclei

    M. Yosoi, H. Akimune, I. Daito, H. Ejiri, H. Fujimura, M. Fujiwara, K. Fushimi, K. Hara, K. Y. Hara, H. Hashimoto, T. Ishikawa, M. Itoh, Y. Itow, S. Kishi, T. Kawabata, K. Kawase, M. Kinoshita, K. Kobayashi, M. Nakamura, K. Nakanishi, Y. Nakatsugawa, S. Nakayama, T. Noro, E. Obayashi, S. Okumura, H. Sakaguchi, Y. Sakemi, M. Shiozawa, H. Takeda, T. Taki, A. Tamii, M. Tanaka, S. Terashima, H. Toyokawa, N. Tsukahara, M. Uchida, T. Yamada, T. Yamagata, Y. Yasuda, H. P. Yoshida, R. G.T. Zegers, J. Zenihiro

    Nuclear Physics A   738 ( 1-4 SUPPL. ) 451 - 454  2004.06

     View Summary

    Decay particles from the s-hole states in 11B, 15N and 6He have been measured in coincidence with the quasifree 12C(p, 2p), 16O(p, 2p) and 7Li(p, 2p) reactions at 392 MeV incident energy. Triton-decay is found to be larger than α-decay for both s-hole states in 11B and 15N despite its smaller Q-value than that, of α-decay. This supports the selection rule predicted by the microscopic SU(3 -model calculations. The relation between the 6He(s-hole) state and the di-triton cluster structure recently found from the charge exchange reaction is briefly discussed. © 2004 Published by Elsevier B.V.

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  • Search for dark matter WIMPs using upward through-going muons in Super-Kamiokande

    S. Desai, Y. Ashie, S. Fukuda, Y. Fukuda, K. Ishihara, Y. Itow, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, T. Ooyabu, C. Saji, M. Earl, E. Kearns, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, M. Goldhaber, T. Barszczak, D. Casper, J. P. Cravens, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, C. W. Sterner, M. R. Vagins, K. S. Ganezer, J. Hill, W. E. Keig, J. Y. Kim, I. T. Lim, R. W. Ellsworth, S. Tasaka, G. Guillian, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, M. D. Messier, Y. Hayato, A. K. Ichikawa, T. Ishida, T. Ishii, T. Iwashita, J. Kameda, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, A. T. Suzuki, M. Hasegawa, K. Hayashi, T. Inagaki, I. Kato, H. Maesaka, T. Morita, T. Nakaya, K. Nishikawa, T. Sasaki, S. Ueda, S. Yamamoto, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, C. K. Jung, T. Kato, K. Kobayashi, M. Malek, C. Mauger, C. McGrew, A. Sarrat

    Physical Review D - Particles, Fields, Gravitation and Cosmology   70 ( 8 )  2004

     View Summary

    We present the results of indirect searches for Weakly Interacting Massive Particles (WIMPs), with 1679.6 live days of data from the Super-Kamiokande detector using neutrino-induced upward through-going muons. The search is performed by looking for an excess of high energy muon neutrinos from WIMP annihilations in the Sun, the core of the Earth, and the Galactic Center, as compared to the number expected from the atmospheric neutrino background. No statistically significant excess was seen. We calculate the flux limits in various angular cones around each of the above celestial objects. We obtain conservative model-independent upper limits on the WIMP-nucleon cross section as a function of WIMP mass, and compare these results with the corresponding results from direct dark matter detection experiments. © 2004 The American Physical Society.

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  • Precise measurement of the solar neutrino day-night and seasonal variation in Super-Kamiokande-I

    M. B. Smy, Y. Ashie, S. Fukuda, Y. Fukuda, K. Ishihara, Y. Itow, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, T. Ooyabu, C. Saji, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, J. Hill, W. E. Keig, J. Y. Kim, I. T. Lim, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, A. K. Ichikawa, T. Ishii, J. Kameda, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, M. Yoshida, T. Iwashita, A. T. Suzuki, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, C. K. Jung, T. Kato, K. Kobayashi, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito, C. Mitsuda, K. Miyano, T. Shibata

    Physical Review D - Particles, Fields, Gravitation and Cosmology   69 ( 1 )  2004

     View Summary

    The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kamiokande-I was fit to the variations expected from active two-neutrino oscillations. The best fit in the large mixing angle solution has a mixing angle of [Formula Presented] and a mass squared difference of [Formula Presented] between the two neutrino mass eigenstates. The fitted day-night asymmetry of [Formula Presented] has improved statistical precision over previous measurements and agrees well with the expected asymmetry of [Formula Presented] © 2004 The American Physical Society.

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  • Search for v̄<inf>e</inf> from the Sun at Super-Kamiokande-I

    Y. Gando, S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, T. Namba, Y. Obayashi, A. Okada, T. Ooyabu, C. Saji, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, J. Hill, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, A. K. Ichikawa, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Oyama, M. Sakuda, M. Yoshida, M. Kohama, T. Iwashita, A. T. Suzuki, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, M. L. Chen, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito, C. Mitsuda, K. Miyano, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, H. I. Kim, S. B. Kim

    Physical Review Letters   90 ( 17 )  2003.05

     View Summary

    A search for v̄e flux from the Sun was performed using all 1496 live days of solar neutrino data from Super-Kamiokande-I. Using the 8B and monochromatic energy spectra, 90% C.L. upper limits were set for the v̄e flux. For the 8B spectrum dependent analysis, the upper limit to the flux was 0.8% of the SSM ve flux prediction for E=8.0-20.0 MeV.

  • The Super-Kamiokande detector

    S. Fukuda, Y. Fukuda, T. Hayakawa, E. Ichihara, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, T. Namba, Y. Obayashi, A. Okada, M. Oketa, K. Okumura, T. Oyabu, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, S. Desai, M. Earl, J. T. Hong, E. Kearns, M. Masuzawa, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, K. Scholberg, T. Barszczak, D. Casper, D. W. Liu, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, S. Mine, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, Y. Hayato, T. Ishii, A. Ichikawa, J. Kanzaki, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, T. Iwashita, M. Kohama, A. T. Suzuki, M. Hasegawa, T. Inagaki, I. Kato, H. Maesaka, T. Nakaya, K. Nishikawa, S. Yamamoto, T. J. Haines, B. K. Kim, R. Sanford, R. Svoboda, E. Blaufuss, M. L. Chen, Z. Conner, J. A. Goodman, E. Guillian, G. W. Sullivan, D. Turcan, A. Habig, M. Ackerman, F. Goebel, J. Hill

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   501 ( 2-3 ) 418 - 462  2003.04

     View Summary

    Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons. During the period April, 1996 to July, 2001, Super-Kamiokande I collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency. These data provided crucial information for our current understanding of neutrino oscillations, as well as setting stringent limits on nucleon decay. In this paper, we describe the detector in detail, including its site, configuration, data acquisition equipment, online and offline software, and calibration systems which were used during Super-Kamiokande I. © 2003 Elsevier Science B.V. All rights reserved.

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  • Tracking performance of the scintillating fiber detector in the K2K experiment

    BJ Kim, T Iwashita, T Ishida, EJ Jeon, H Yokoyama, S Aoki, HG Berns, HC Bhang, S Boyd, K Fujii, T Hara, Y Hayato, J Hill, T Ishii, H Ishino, CK Jung, E Kearns, HI Kim, JH Kim, JY Kim, SB Kim, T Kobayashi, G Kume, S Matsuno, S Mine, K Nakamura, M Nakamura, K Nishikawa, M Onchi, T Otaki, Y Oyama, H Park, M Sakuda, K Sato, K Scholberg, E Sharkey, JL Stone, A Suzuki, K Takenaka, N Tamura, Y Tanaka, M Takatsuki, CW Walter, J Wilkes, J Yoo, M Yoshida

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   497 ( 2-3 ) 450 - 466  2003.02  [Refereed]

     View Summary

    The K2K long-baseline neutrino oscillation experiment uses a Scintillating Fiber Detector (SciFi) to reconstruct charged particles produced in neutrino interactions in the near detector. We describe the track reconstruction algorithm and the performance of the SciFi after 3 years of operation. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Polarization transfer in the O-16(p, p ') reaction at forward angles and structure of the spin-dipole resonances

    T Kawabata, H Akimune, GPA Berg, BA Brown, H Fujimura, H Fujita, Y Fujita, M Fujiwara, K Hara, K Hatanaka, K Hosono, T Ishikawa, A Itoh, J Kamiya, A Nakamura, T Noro, E Obayashi, H Sakaguchi, Y Shimbara, H Takeda, T Taki, A Tamii, H Toyokawa, A Uchida, H Ueno, T Wakasa, K Yamasaki, Y Yasuda, HP Yoshida, M Yosoi

    SPIN 2002   675   681 - 685  2003  [Refereed]

     View Summary

    Cross sections and polarization transfer observables in the O-16(p,p') reactions at 392 MeV were measured at forward angles including 0degrees. The non-spin-flip (DeltaS = 0) and spin-flip (DeltaS = 1) strengths in transitions to several discrete states and broad resonances in O-16 were extracted using a model-independent method. The giant resonances in the energy region of E-x = 19-27 MeV were found to be predominantly excited by DeltaL = 1 transitions. The strength distribution of spin-dipole transitions with DeltaS = 1 and DeltaL = 1 were deduced. The obtained distribution was compared with a recent shell model calculation. Experimental results are reasonably explained by distorted-wave impulse-approximation calculations with the shell model wave functions.

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  • Study of the spin dependent He-3-nucleus interaction at 450 MeV

    J Kamiya, K Hatanaka, Y Sakemi, T Wakasa, HP Yoshida, E Obayashi, K Hara, Y Kitamura, Y Shimizu, K Fujita, N Sakamoto, H Sakaguchi, M Yosoi, M Uchida, Y Yasuda, Y Shimbara, T Adachi, T Noro, T Kawabata

    SPIN 2002   675   691 - 695  2003  [Refereed]

     View Summary

    The cross sections and analyzing powers were measured for He-3+C-12, Ni-58, and Zr-90 elastic scattering at T-3He=450 MeV. The incident energy dependence of the volume integral per nucleon for He-3 shows the similar behavior to that of protons if the spin-orbit potential is taken into account. This result supports the assumption that interactions between He-3 and nucleus are dominated by the interactions between constituent nucleons of He-3 and target nucleus in the intermediate energy region. The results of the single folding calculation suggest the interaction between point nucleon and target nucleus is modified in the He-3+nucleus elastic scattering.

  • Extraction of neutron density distributions from proton elastic scattering at intermediate energies

    H Takeda, H Sakaguchi, S Terashima, T Taki, A Yosoi, M Itoh, T Kawabata, T Ishikawa, M Uchida, N Tsukahara, Y Yasuda, T Noro, M Yoshimura, H Fujimura, HP Yoshida, E Obayashi, A Tamii, H Akimune

    SPIN 2002   675   720 - 724  2003  [Refereed]

     View Summary

    Cross sections, analyzing powers and spin rotation parameters of proton elastic scattering front Ni-58 and Sn-120 have been measured at intermediate energies. Obtained data have been analyzed in the framework of relativistic impulse approximations. In order to explain the Ni-58 data, it was necessary to modify NN interactions in the nuclear medium by changing coupling constants and masses of sigma and omega mesons. For Sn-120, by assuming the same modification of NN interactions and by using proton densities deduced from charge densities, the neutron density distribution was searched so as to reproduce Sn-120 data at 300 MeV.

  • High resolution study of pionic 0(-) state in O-16

    T Wakasa, GPA Berg, H Fujimura, K Fujita, K Hatanaka, M Itoh, J Kamiya, T Kawabata, Y Kitamura, E Obayashi, H Sakaguchi, N Sakamoto, Y Sakemi, Y Shimizu, H Takeda, M Uchida, Y Yasuda, HP Yoshida, M Yosoi

    SPIN 2002   675   676 - 680  2003  [Refereed]

     View Summary

    The cross sections and analyzing powers of the O-16(p,p')O-16(0(-),T = 1) scattering were measured at a bombarding energy of 295 MeV and an angular range of 14degrees less than or equal to theta(lab) less than or equal to 30degrees. The isovector 0(-) state at E-x = 12.80 MeV is clearly separated from the neighboring states with an energy resolution of DeltaE similar or equal to 30 keV. The data have been compared with distorted wave impulse approximation (DWIA) calculations. The analyzing powers are sensitve to the effective nucleon-nucleon (NN) interaction used in DWIA calculations, and our data support the medium modification of the NN interaction in nuclei. The DWIA calculation employing a random phase approximation (RPA) response function predicts an enhancement of the cross sections around a momentum transfer of q similar or equal to 1.7 fm(-1), and it gives a reasonable agreement with the data.

  • Search for [Formula presented] from the Sun at Super-Kamiokande-I

    Y. Gando, S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, T. Namba, Y. Obayashi, A. Okada, T. Ooyabu, C. Saji, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, J. Hill, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, A. K. Ichikawa, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Oyama, M. Sakuda, M. Yoshida, M. Kohama, T. Iwashita, A. T. Suzuki, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, M. L. Chen, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito, C. Mitsuda, K. Miyano, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, H. I. Kim, S. B. Kim

    Physical Review Letters   90 ( 17 ) 5  2003

     View Summary

    We present the results of a search for low energy [Formula presented] from the Sun using 1496 days of data from Super-Kamiokande-I. We observe no significant excess of events and set an upper limit for the conversion probability to [Formula presented] of the [Formula presented] solar neutrino. This conversion limit is [Formula presented] ([Formula presented] C.L.) of the standard solar model’s neutrino flux for total [Formula presented]. We also set a flux limit for monochromatic [Formula presented] for [Formula presented]. © 2003 The American Physical Society.

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  • Indications of Neutrino Oscillation in a 250 km Long-Baseline Experiment

    M. H. Ahn, S. Aoki, H. Bhang, S. Boyd, D. Casper, J. H. Choi, S. Fukuda, Y. Fukuda, W. Gajewski, T. Hara, M. Hasegawa, T. Hasegawa, Y. Hayato, J. Hill, A. K. Ichikawa, A. Ikeda, T. Inagaki, T. Ishida, T. Ishii, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, J. S. Jang, E. J. Jeon, C. K. Jung, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, E. Kearns, A. Kibayashi, D. Kielczewska, K. Kobayashi, B. J. Kim, C. O. Kim, J. Y. Kim, S. B. Kim, T. Kobayashi, M. Kohama, Y. Koshio, W. R. Kropp, J. G. Learned, S. H. Lim, I. T. Lim, H. Maesaka, K. Martens, T. Maruyama, S. Matsuno, C. Mauger, C. McGrew, S. Mine, M. Miura, K. Miyano, S. Moriyama, M. Nakahata, K. Nakamura, I. Nakano, F. Nakata, T. Nakaya, S. Nakayama, T. Namba, K. Nishikawa, S. Nishiyama, S. Noda, A. Obayashi, A. Okada, T. Ooyabu, Y. Oyama, M. Y. Pac, H. Park, M. Sakuda, N. Sakurai, N. Sasao, K. Scholberg, E. Sharkey, M. Shiozawa, H. So, H. W. Sobel, A. Stachyra, J. L. Stone, Y. Suga, L. R. Sulak, A. Suzuki, Y. Suzuki, Y. Takeuchi, N. Tamura, T. Toshito, Y. Totsuka, M. R. Vagins, C. W. Walter, R. J. Wilkes, S. Yamada, S. Yamamoto, C. Yanagisawa, H. Yokoyama, J. Yoo, M. Yoshida, J. Zalipska

    Physical Review Letters   90 ( 4 ) 5 - 418015  2003

     View Summary

    The K2K experiment observes indications of neutrino oscillation: a reduction of [Formula presented] flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of [Formula presented]. Twenty-nine one ring [Formula presented]-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%. © 2003 The American Physical Society.

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  • Search for Supernova Relic Neutrinos at Super-Kamiokande

    M. Malek, M. Morii, S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, T. Namba, A. Okada, T. Ooyabu, C. Saji, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Obayashi, Y. Oyama, M. Sakuda, M. Yoshida, M. Kohama, T. Iwashita, A. T. Suzuki, A. Ichikawa, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito, C. Mitsuda, K. Miyano, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, H. I. Kim, S. B. Kim, J. Yoo

    Physical Review Letters   90 ( 6 ) 5  2003

     View Summary

    A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to [Formula presented]. Additionally, an upper bound of [Formula presented] was set for the supernova relic neutrino flux in the energy region [Formula presented]. © 2003 The American Physical Society.

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  • Search for periodic modulations of the solar neutrino flux in Super-Kamiokande-I

    J. Yoo, Y. Ashie, S. Fukuda, Y. Fukuda, K. Ishihara, Y. Itow, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, T. Namba, R. Nambu, Y. Obayashi, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, S. Yamada, M. Ishitsuka, T. Kajita, K. Kaneyuki, S. Nakayama, A. Okada, T. Ooyabu, C. Saji, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, J. Hill, W. E. Keig, J. Y. Kim, I. T. Lim, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, A. K. Ichikawa, T. Ishii, J. Kameda, T. Kobayashi, T. Maruyama, K. Nakamura, K. Nitta, Y. Oyama, M. Sakuda, Y. Totsuka, M. Yoshida, M. Kohama, T. Iwashita, A. T. Suzuki, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, M. L. Chen, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, M. Ackermann, C. K. Jung, T. Kalo, K. Kobayashi, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito

    Physical Review D   68 ( 9 )  2003

     View Summary

    A search for periodic modulations of the solar neutrino flux was performed using the Super-Kamiokande-I data taken from 31 May 1996 to 15 July 2001. The detector's capability of measuring the exact time of events, combined with a relatively high yield of solar neutrino events, allows a search for short-time variations in the observed flux. We employed the Lomb test to look for periodic modulations of the observed solar neutrino flux. The obtained periodogram is consistent with statistical fluctuation and no significant periodicity was found. © 2003 The American Physical Society.

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  • Search for neutrinos from gamma-ray bursts using Super-Kamiokande

    S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, S. Desai, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, W. Wang, M. Goldhaber, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, Y. Hayato, A. Ichikawa, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Obayashi, Y. Oyama, M. Sakuda, M. Yoshida, T. Iwashita, M. Kohama, A. T. Suzuki, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, R. Svoboda, E. Blaufuss, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, K. Scholberg, A. Habig, J. Hill, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, C. Mitsuda, K. Miyano, C. Saji, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, H. I. Kim, S. B. Kim, J. Yoo, H. Okazawa, T. Ishizuka, M. Etoh, Y. Gando, T. Hasegawa, K. Inoue, K. Ishihara, I. Nishiyama

    Astrophysical Journal   578 ( 1 I ) 317 - 324  2002.10

     View Summary

    Using the Super-Kamiokande neutrino observatory, a search was conducted for neutrinos produced in coincidence with gamma-ray bursts observed by the Burst and Transient Source Experiment detector. Super-Kamiokande data in the neutrino energy range of 7 MeV ∼ 100 TeV were analyzed. For gamma-ray bursts that occurred between 1996 April and 2000 May, no statistically significant signal in excess of the background levels was detected. Implied upper limits on associated gamma-ray burst neutrino production are presented.

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  • Determination of solar neutrino oscillation parameters using 1496 days of Super-Kamiokande-I data

    S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, T. Namba, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, M. B. Smy, H. W. Sobel, M. R. Vagins, A. Gago, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, T. Maruyama, K. Nakamura, Y. Obayashi, Y. Oyama, M. Sakuda, M. Yoshida, M. Kohama, T. Iwashita, A. T. Suzuki, A. Ichikawa, T. Inagaki, I. Kato, T. Nakaya, K. Nishikawa, T. J. Haines, S. Dazeley, S. Hatakeyama, R. Svoboda, E. Blaufuss, M. L. Chen, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turčan, K. Scholberg, A. Habig, M. Ackermann, J. Hill, C. K. Jung, M. Malek, K. Martens, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, T. Toshito, C. Mitsuda, K. Miyano, C. Saji, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takitat, H. I. Kim, S. B. Kim, J. Yoo, H. Okazawa

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   539 ( 3-4 ) 179 - 187  2002.07

     View Summary

    A number of different fits to solar neutrino mixing and mass square difference were performed using 1496 days of Super-Kamiokande-I's solar neutrino data. These data select two allowed areas at large neutrino mixing when combined with either the solar 8B flux prediction of the standard solar model or the SNO interaction rate measurements. A global fit combining SK data with the solar neutrino interaction rates measured by Homestake, SNO, Gallex/GNO and SAGE prefers a single allowed area, the Large Mixing Angle solution, at the 98.9% confidence level. The mass square difference Δm2 between the two mass eigenstates ranges from about 3 to 19 × 10-5 eV2, while the mixing angle θ is in the range of tan2θ ≈ 0.25-0.65. © 2002 Elsevier Science B.V. All rights reserved.

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  • The isoscalar giant dipole resonance in Pb-208 and the nuclear incompressibility

    M Hedden, U Garg, B Kharraja, S Zhu, M Uchida, H Sakaguchi, T Murakami, M Yosoi, H Takeda, M Itoh, T Kawabata, T Taki, T Ishikawa, N Tsukuhara, Y Yasuda, M Fujiwara, H Fujimura, HP Yoshida, E Obayashi, K Hara, H Akimune, MN Harakeh, M Volkerts

    NUCLEAR PHYSICS IN THE 21ST CENTURY   610   880 - 884  2002  [Invited]

     View Summary

    The isoscalar giant dipole resonnace (ISGDR) has been investigated in Pb-208 using inelastic scattering of 400 MeV alpha particles at extremely forward angles, including 0degrees. Using the superior capabilities of the Grand Raiden spectrometer, it has been possible to obtain inelastic spectra devoid of any "instrumental" background. The ISGDR strength distribution has been extracted from a multipole-decomposition of the observed spectra. The implications of these results on the experimental value of nuclear incompressibility are discussed.

  • Atmospheric gamma-ray observation with the BETS detector for calibrating atmospheric neutrino flux calculations

    K. Kasahara, E. Mochizuki, S. Torii, T. Tamura, N. Tateyama, K. Yoshida, T. Yamagami, Y. Saito, J. Nishimura, H. Murakami, T. Kobayashi, Y. Komori, M. Honda, T. Ohuchi, S. Midorikawa, T. Yuda

    Physical Review D - Particles, Fields, Gravitation and Cosmology   66 ( 5 )  2002  [Refereed]

     View Summary

    We observed atmospheric gamma rays around 10 GeV at balloon altitudes (15–25 km) and at a mountain (2770 m a.s.l). The observed results were compared with Monte Carlo calculations to find that an interaction model (Lund FRITIOF1.6) used in an old neutrino flux calculation was not good enough for describing the observed values. Instead, we found that two other nuclear interaction models, Lund FRITIOF7.02 and DPMJET3.03, gave much better agreement with the observations. Our data will serve for examining nuclear interaction models and for deriving a reliable absolute atmospheric neutrino flux in the GeV region. © 2002 The American Physical Society.

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  • Extraction of neutron density distributions from proton elastic scattering at intermediate energies

    H Takeda, H Sakaguchi, T Taki, M Yosoi, M Itoh, T Kawabata, T Ishikawa, M Uchida, N Tsukahara, T Noro, M Yoshimura, H Fujimura, HP Yoshida, E Obayashi, A Tamii, H Akimune

    NUCLEAR PHYSICS IN THE 21ST CENTURY   610   648 - 652  2002  [Refereed]

     View Summary

    Cross sections, analyzing powers and spin rotation parameters of proton elastic scattering from Ni-58 and Sn-120 have been measured at intermediate energies. In order to explain the Ni-58 data, it was necessary to use experimental density distributions deduced from charge distributions and to modify coupling constants and masses of sigma and omega mesons. For Sn-120, assuming the same modification and using proton densities deduced from charge densities, neutron density distribution was searched so as to reproduce Sn-120 data. Effects of rho meson modifications are also discussed.

  • Detection of accelerator-produced neutrinos at a distance of 250 km

    S. H. Ahn, S. An, S. Aoki, H. G. Berns, H. C. Bhang, S. Boyd, D. Casper, T. Chikamatsu, J. H. Choi, S. Echigo, M. Etoh, K. Fujii, S. Fukuda, Y. Fukuda, W. Gajewski, U. Golebiewska, T. Hara, T. Hasegawa, Y. Hayato, J. Hill, S. J. Hong, M. Ieiri, T. Inada, T. Inagaki, T. Ishida, H. Ishii, T. Ishii, H. Ishino, M. Ishitsuka, Y. Itow, T. Iwashita, H. I. Jang, J. S. Jang, E. J. Jeon, E. M. Jeong, C. K. Jung, T. Kadowaki, T. Kajita, J. Kameda, K. Kaneyuki, I. Kato, Y. Kato, E. Kearns, S. Kenmochi, B. H. Khang, A. Kibayashi, D. Kielczewska, B. J. Kim, C. O. Kim, H. I. Kim, J. H. Kim, J. Y. Kim, S. B. Kim, S. Kishi, M. Kitamura, K. Kobayashi, T. Kobayashi, Y. Kobayashi, M. Kohama, D. G. Koo, Y. Koshio, W. Kropp, G. Kume, E. Kusano, J. G. Learned, H. K. Lee, J. W. Lee, S. B. Lee, I. T. Lim, S. H. Lim, H. Maesaka, K. Martens, T. Maruyama, S. Matsuno, C. Mauger, C. McGrew, M. Minakawa, S. Mine, M. Miura, S. Miyamoto, K. Miyano, S. Moriyama, S. Mukai, M. Nakahata, K. Nakamura, M. Nakamura, I. Nakano, T. Nakaya, S. Nakayama, K. Nakayoshi, K. Nishijima, K. Nishikawa, S. Nishiyama, S. Noda, H. Noumi, Y. Obayashi, J. K. Oh, A. Okada, M. Onchi, T. Otaki

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   511 ( 2-4 ) 178 - 184  2001.07

     View Summary

    The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time of the beam in the 22.5 kt fiducial volume of Super-Kamiokande, the far detector at 250 km distance. The expectation is 37.8-3.8+3.5, derived using measurements of neutrino interactions in a near detector and extrapolation using a beam simulation validated by a measurement of pion kinematics after production and focusing. The background is of order 10-3 events. © 2001 Elsevier Science B.V.

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  • Constraints on neutrino oscillations using 1258 days of super-kamiokande solar neutrino data

    S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, L. R. Price, M. B. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, K. Nakamura, Y. Obayashi, Y. Oyama, A. Sakai, M. Sakuda, M. Kohama, A. T. Suzuki, T. Inagaki, T. Nakaya, K. Nishikawa, T. J. Haines, E. Blaufuss, S. Dazeley, K. B. Lee, R. Svoboda, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, A. Habig, J. Hill, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, C. Mitsuda, K. Miyano, C. Saji, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, M. Yoshida, H. I. Kim, S. B. Kim, J. Yoo, H. Okazawa, T. Ishizuka, M. Etoh, Y. Gando, T. Hasegawa, K. Inoue, K. Ishihara

    Physical Review Letters   86 ( 25 ) 5656 - 5660  2001.06

     View Summary

    The neutrino oscillations of the recoil electron energy spectrum and zenith angle variations of the solar neutrino flux were presented using precise measurements from 1258 days of neutrino-electron scattering data in Super-Kamiokande. A strong constraint on neutrino mixing and mass difference in a flux-independent way was obtained due to the absence of zenith angle variation and spectrum distortion. It was shown that two allowed regions at large mixing were obtained using the Super-Kamiokande flux measurement.

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  • Solar 8b and hep neutrino measurements from 1258 days of super-kamiokande data

    Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, S. Desai, M. Earl, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, D. W. Liu, L. R. Price, M. B. Smy, H. W. Sobel, M. R. Vagins, T. J. Haines, D. Kielczewska, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, K. Nakamura, Y. Obayashi, Y. Oyama, A. Sakai, M. Sakuda, M. Kohama, A. T. Suzuki, T. Inagaki, T. Nakaya, K. Nishikawa, T. J. Haines, E. Blaufuss, S. Dazeley, R. Svoboda, E. Blaufuss, J. A. Goodman, G. Guillian, G. W. Sullivan, D. Turcan, A. Habig, J. Hill, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, C. Mitsuda, K. Miyano, C. Saji, T. Shibata, Y. Kajiyama, Y. Nagashima, K. Nitta, M. Takita, M. Yoshida, H. I. Kim, S. B. Kim, J. Yoo, H. Okazawa, T. Ishizuka, M. Etoh, Y. Gando, T. Hasegawa, K. Inoue

    Physical Review Letters   86 ( 25 ) 5651 - 5655  2001.06

     View Summary

    Solar neutrino measurements were presented from 1258 days of Super-Kamiokande detector data. The measurements based on recoil electrons in the energy range 5.0-20.0 MeV were performed. The recoil electron energy spectrum was found to be consistent with no spectral distortion. A stringent limit on the hep neutrino flux was obtained, which was found to be 4.3 times the predicted value from BP2000.

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  • 16N as a calibration source for Super-Kamiokande

    E. Blaufuss, G. Guillian, Y. Fukuda, S. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, K. Nakamura, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. Inagaki, K. Nishikawa, T. J. Haines, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, M. Kirisawa, S. Inaba, C. Mitsuda, K. Miyano, H. Okazawa, C. Saji, M. Takahashi, M. Takahata, Y. Nagashima, K. Nitta, M. Takita, M. Yoshida, S. B. Kim, M. Etoh, Y. Gando, T. Hasegawa, K. Inoue

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   458 ( 3 ) 638 - 649  2001.02

     View Summary

    The decay of 16N is used to cross check the absolute energy scale calibration for solar neutrinos established by the electron linear accelerator (LINAC). A deuterium-tritium neutron generator was employed to create 16N via the (n,p) reaction on 16O in the water of the detector. This technique is isotropic and has different systematic uncertainties than the LINAC. The results from this high-statistics data sample agree with the absolute energy scale of the LINAC to better than 1%. A natural source of 16N from the capture of μ- on 16O, which is collected as a background to the solar neutrino analysis, is also discussed.

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  • Calorimetric electron telescope (calet) for the Japanese exposure facility on the ISS

    K. Yoshida, S. Torii, N. Tateyama, T. Tamura, T. Ouchi, T. Kashiwagi, K. Hibino, J. Nishimura, T. Yamagami, Y. Saito, H. Murakami, T. Kobayashi, Y. Komori, K. Kasahara, T. Yuda, M. Ohnishi, M. Shibata, F. Makino

    Advances in Space Research   27 ( 4 ) 681 - 686  2001  [Refereed]

     View Summary

    The CALET (CALorimetric Electron Telescope) instrument is proposed for the observation of TeV electrons at the Japanese Experiment Module Exposure Facility (JEM/EF) on the ISS, which is composed of an imaging calorimeter with scintillating fibers and lead plates, and a total absorption calorimeter with BGO logs. Since TeV electrons could reach only from the nearby sources within a distance less than 1 kpc, we can expect that the energy spectrum has a structural component and the arrival directions show an anisotropy. Therefore, we should be able to localize and identify the nearby cosmic-ray sources by the TeV electron observation. We report the status of development of the CALET instrument, which has a capability to observe electrons up to 10 TeV and a proton rejection power of ~ 10 6 . We expect to observe ~ 10 3 events over 1 TeV during the 3 years observation. By using the excellent imaging capability of the CALET, gamma-rays over the GeV region and the nuclear components up to 10 15 eV might also be observed. © 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

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  • Instrumentation for the polarization transfer experiment in proton inelastic scattering at 0 degrees

    M Yosoi, H Akimune, Daito, I, H Fujimura, Y Fujita, M Fujiwara, K Hatanaka, K Hosono, T Inomata, T Ishikawa, M Itoh, M Kawabata, T Kawabata, M Nakamura, T Noro, E Obayashi, H Sakaguchi, H Takeda, T Taki, A Tamii, H Toyokawa, M Uchida, HP Yoshida, M Yoshimura

    SPIN 2000   570   765 - 769  2001  [Refereed]

     View Summary

    We have constructed an experimental ensemble to measure polarization transfer observables in proton inelastic scattering at zero degrees. Excited states can simultaneously be measured for the excitation energy from 5 MeV to 35 MeV at E-p=400 MeV. A fast data acquisition system has been developed to endure the large background event rate originated by the primary beam itself. We have found the effective analyzing power of the focal plane polarimeter slightly depends on the treatment of two-ray events.

  • Spin-dependent effective interaction studied by the C-12, Si-28((p)over-right-arrow, (p)over-right-arrow ') reactions at zero degrees

    A Tamii, T Kawabata, H Akimune, Daito, I, Y Fujita, M Fujiwara, K Hatanaka, K Hosono, F Ihara, T Inomata, T Ishikawa, M Itoh, M Kawabata, M Nakamura, T Noro, E Obayashi, H Sakaguchi, H Takeda, T Taki, H Toyokawa, HP Yoshida, M Yoshimura, R Yosoi

    SPIN 2000   570   639 - 643  2001  [Refereed]

     View Summary

    Polarization transfer (PT) coefficients in the C-12, Si-28(p,p ') reactions at a scattering angle of 0 degrees are measured at E-p = 392 MeV. The strength of the isoscalar central spin-dependent part (V-sigma) of the effective nucleon-nucleon interaction is studied by using the sensitivity of the PT coefficients for the excitation of the 1(+), T=0 state in C-12 to the V-sigma strength. It is found that distorted wave impulse approximation (DWIA) calculations employing the Franey and Love effective interaction well reproduce the measured PT coefficients.

  • Neutron densities in Sn-120 observed by polarized proton scattering

    H Sakaguchi, H Takeda, T Taki, M Yosoi, M Itoh, T Kawabata, T Ishikawa, M Uchida, N Tsukahara, T Noro, M Yoshimura, H Fujimura, H Yoshida, E Obayashi, A Tamii, H Akimune

    SPIN 2000   570   604 - 608  2001  [Refereed]

     View Summary

    Cross sections, analyzing powers and spin rotation parameters of proton elastic scattering from Ni-58 and Sn-120 have been measured at intermediate energies. By elastic scattering off N similar or equal toZ nulcei like 58Ni at intermediate energies we can study medium modification of the nucleon-nucleon (NN) interaction inside the nucleus, because proton distributions in target nuclei are constrained by charge distributions measured by electron scattering and neutron distributions can be assumed to be the same as proton's. In order to explain our experimental data of Ni-58 at large scattering angles, it was found to be necessary to use experimental densities deduced from charge densities measured by electron scattering and to modify the coupling constants and the masses of exchanged sigma and omega mesons in the RIA, assuming linear dependencies of meson propeties to nuclear densities. Parameters of the medium effect have been searched to reproduce the data.
    For N not equalZ nuclei, neutron density distribution can be extracted from the elastic scattering, assuming the same medium modifications fixed by the Ni-58 data and using proton distributions obtained from charge distributions. We have searched neutron density distribution so as to reproduce Sn-120 data at the proton incident energy of 300 MeV. Deduced neutron distribution has an increase at the nuclear center, which is consistent with the 3s(1/2) orbit wave function as expected in Sn-120. At energies other than 300 MeV, experimental data of Sn-120 have been also well reproduced by the neutron distribution obtained at 300 MeV.

  • Tau neutrinos favored over sterile neutrinos in atmospheric muon neutrino oscillations

    S. Fukuda, Y. Fukuda, M. Ishitsuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, T. Toshito, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, D. Takemori, Y. Hayato, T. Ishii, T. Kobayashi, K. Nakamura, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, M. Kohama, A. T. Suzuki, T. Inagaki, K. Nishikawa, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. Guillian, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, M. Malek, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, M. Kirisawa, S. Inaba, C. Mitsuda, K. Miyano, H. Okazawa, C. Saji, M. Takahashi, M. Takahata, Y. Nagashima, K. Nitta, M. Takita, M. Yoshida, S. B. Kim, T. Ishizuka, M. Etoh, Y. Gando, T. Hasegawa, K. Inoue, K. Ishihara, T. Maruyama

    Physical Review Letters   85 ( 19 ) 3999 - 4003  2000.11

     View Summary

    Three dependent data samples that discriminate between the oscillations to either tau neutrinos or sterile neutrinos in the region of mixing angle and Δm2 preferred by the majority of the Super-Kamiokande data are presented. Results show that two-flavor oscillation between muon neutrinos and sterile neutrinos fit the low energy charged current data, but do not fit the neutral current or high energy data. More complicated scenarios in which both νμ↔ντ and νμ↔νs oscillations that coexist with small mixing to sterile neutrinos or with much smaller mass differences for sterile neutrinos are considered.

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  • Design, construction, and operation of SciFi tracking detector for K2K experiment

    A. Suzuki, H. Park, S. Aoki, S. Echigo, K. Fujii, T. Hara, T. Iwashita, M. Kitamura, M. Kohama, G. Kume, M. Onchi, T. Otaki, K. Sato, M. Takatsuki, K. Takenaka, Y. Tanaka, K. Tashiro, T. Inagaki, I. Kato, S. Mukai, T. Nakaya, K. Nishikawa, N. Sasao, A. Shima, H. Yokoyama, T. Chikamatsu, Y. Hayato, T. Ishida, T. Ishii, H. Ishino, E. J. Jeon, T. Kobayashi, S. B. Lee, K. Nakamura, Y. Oyama, A. Sakai, M. Sakuda, V. Tumakov, S. Fukuda, Y. Fukuda, M. Ishizuka, Y. Itow, T. Kajita, J. Kameda, K. Kaneyuki, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, T. Toshito, S. Yamada, K. Miyano, M. Nakamura, N. Tamura, I. Nakano, M. Yoshida, T. Kadowaki, S. Kishi, H. Yokoyama, T. Maruyama, M. Etoh, K. Nishijima, H. C. Bhang, B. H. Khang, B. J. Kim, H. I. Kim, J. H. Kim, S. B. Kim, H. So, J. H. Yoo, J. H. Choi, H. I. Jang, J. S. Jang, J. Y. Kim, I. T. Lim, M. Y. Pac, E. Kearns, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, D. Casper, W. Gajewski, W. Kropp, S. Mine, H. Sobel, M. Vagins, S. Matsuno, J. Hill

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   453 ( 1-2 ) 165 - 176  2000.10

     View Summary

    We describe the construction and performance of a scintillating fiber detector used in the near detector for the K2K (KEK to Kamioka, KEK E362) long baseline neutrino oscillation experiment. The detector uses 3.7 m long and 0.692 mm diameter scintillating fiber coupled to image-intensifier tubes (IIT), and a CCD camera readout system. Fiber sheet production and detector construction began in 1997, and the detector was commissioned in March 1999. Results from the first K2K runs confirm good initial performance: position resolution is estimated to be about 0.8 mm, and track finding efficiency is 98±2% for long tracks (i.e., those which intersect more than 5 fiber planes). The hit efficiency was estimated to be 92±2% using cosmic-ray muons, after noise reduction at the offline stage. The possibility of using the detector for particle identification is also discussed.

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  • Neutron Density Distributions Observed by Proton Elastic Scattering

    H. Takeda, H. Sakaguchi, T. Taki, M. Yosoi, M. Itoh, T. Kawabata, T. Ishikawa, M. Uchida, N. Tsukahara, T. Noro, M. Yoshimura, H. Fujimura, H. Yoshida, E. Obayashi, A. Tamii, H. Akimune

    Proceedings of RCNP-TMU Symposium on Spins in Nuclear and Hadronic Reactions   102 ( 1 ) 35 - 41  2000

     View Summary

    Cross sections, analyzing powers and spin rotation parameters of proton elastic scattering from ^<58>Ni and ^<120>Sn have been measured at intermediate energies. In order to explain the ^<58>Ni data, it was necessary to use experimental density distributions deduced from charge distributions and to modify coupling constants and masses of σ and ω mesons. Assuming the same modification was also valid for ^<120>Sn and using proton densities deduced from charge densities, neutron density distribution was searched so as to reproduce ^<120>Sn data.

    DOI CiNii

  • Performance of the BETS detector for cosmic ray electrons

    T Tamura, S Torii, K Yoshida, T Yamagami, H Murakami, T Kobayashi, K Kasahara, T Yuda, J Nishimura

    SCIENTIFIC BALLOONING   26 ( 9 ) 1397 - 1400  2000  [Refereed]

     View Summary

    Performance of BETS detector as an electron imaging calorimeter was studied by electron and proton beams at CERN-SPS in 1996 and 1997. It is confirmed that the rejection power against proton backgrounds is better than 4x10(-4) in the energy range between 10 GeV and 100 GeV, the energy resolution ranges 15 similar to 18 %, and the angular resolution is 0 degrees.8 similar to 1 degrees.3. The balloon flights were carried out in 1995, 1997, and 1998 at the Sanriku Balloon Center in Japan. It is demonstrated in the flight data that the performance is adequate for observing electrons with reliable accuracy. (C) 2000 COSPAR. Published by Elsevier Science Ltd.

  • Calibration of Super-Kamiokande using an electron LINAC

    M. Nakahata, Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, K. Martens, M. Miura, S. Nakayama, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, S. Mine, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, K. Miyano, H. Okazawa, C. Saji, M. Takahata, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa, T. Hasegawa, S. Hatakeyama

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   421 ( 1-2 ) 113 - 129  1999.01

     View Summary

    In order to calibrate the Super-Kamiokande experiment for solar neutrino measurements, a linear accelerator (LINAC) for electrons was installed at the detector. LINAC data were taken at various positions in the detector volume, tracking the detector response in the variables relevant to solar neutrino analysis. In particular, the absolute energy scale is now known with less than 1% uncertainty. © 1999 Elsevier Science B.V. All rights reserved.

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  • Constraints on neutrino oscillation parameters from the measurement of day-night solar neutrino fluxes at super-kamiokande

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kerns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, S. Mine, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, K. Miyano, H. Okazawa, C. Saji, M. Takahata, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa, T. Hasagawa, S. Hatakeyama, T. Iwamoto

    Physical Review Letters   82 ( 9 ) 1810 - 1814  1999

     View Summary

    A search for day-night variations in the solar neutrino flux resulting from neutrino oscillations has been carried out using the 504 day sample of solar neutrino data obtained at Super-Kamiokande. The absence of a significant day-night variation has set an absolute flux independent exclusion region in the two neutrino oscillation parameter space. © 1999 The American Physical Society.

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  • Neutrino-induced upward stopping muons in Super-Kamiokande

    Y. Fukuda, K. Ishihara, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, H. Ishino, T. Kobayashi, K. Nakamura, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. Inagaki, K. Nishikawa, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, M. Kirisawa, S. Inaba, K. Miyano, H. Okazawa, C. Saji, M. Takahashi, M. Takahata, K. Higuchi, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, A. Hasegawa, T. Hasegawa, S. Hatakeyama, K. Inoue, T. Iwamoto, M. Koga, T. Maruyama

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   467 ( 3-4 ) 185 - 193  1999

     View Summary

    A total of 137 upward stopping muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 516 detector live days. The measured muon flux is 0.39 ± 0.04(stat.) ± 0.02(syst.) × 10-13 cm-2s-1sr-1 compared to an expected flux of 0.73 ± 0.16(theo.) × 10-13 cm-2s-1sr-1. Using our previously-published measurement of the upward through-going muon flux, we calculate the stopping/through-going flux ratio ℛ, which has less theoretical uncertainty. The measured value of ℛ = 0.22 ± 0.02(stat.) ± 0.01(syst.) is significantly smaller than the value 0.37-0.04+0.05(theo.) expected using the best theoretical information (the probability that the measured ℛ is a statistical fluctuation below the expected value is 0.39%). A simultaneous fitting to zenith angle distributions of upward stopping and through-going muons gives a result which is consistent with the hypothesis of neutrino oscillations with the parameters sin22θ > 0.7 and 1.5 × 10-3 < Δm2 < 1.5 × 10-2 eV2 at 90% confidence level, providing a confirmation of the observation of neutrino oscillations by Super-Kamiokande using the contained atmospheric neutrino events. © 1999 Published by Elsevier Science B.V. All rights reserved.

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  • Observation of the East-West anisotropy of the atmospheric neutrino flux

    T. Futagami, Y. Fukuda, T. Hayakawa, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, M. Kirisawa, S. Inaba, K. Miyano, H. Okazawa, C. Saji, M. Takahashi, M. Takahata, K. Higuchi, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto

    Physical Review Letters   82 ( 26 ) 5194 - 5197  1999

     View Summary

    The east-west anisotropy, caused by the deflection of primary cosmic rays in the Earth's magnetic field, is observed for the first time in the flux of atmospheric neutrinos. Using a 45 kt yr exposure of the Super-Kamiokande detector, 552 e-like and 633 μ-like horizontally going events are selected in the momentum range between 400 and 3000 MeV/c. The azimuthal distributions of e-like and μ-like events agree with the expectation from atmospheric neutrino flux calculations, verifying that the flux of atmospheric neutrinos in the GeV energy range is reasonably well modeled by calculations that account for the geomagnetic field. © 1999 The American Physical Society.

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  • Measurement of the flux and zenith-angle distribution of upward throughgoing muons by super-kamiokande

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, T. J. Haines, D. Kielczewska, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, S. Mine, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, K. Miyano, H. Okazawa, C. Saji, M. Takahata, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto, M. Koga

    Physical Review Letters   82 ( 13 ) 2644 - 2648  1999

     View Summary

    A total of 614 upward throughgoing muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is [1.74±0.07(stat)±0.02(sys)]×10-13cm-2s-1sr-1 compared to an expected flux of [1.97±0.44(theor)]×10-13cm-2s-1sr-1. The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the vμ⟷vτ oscillation hypothesis with sin22θ> 0.4 and 1×10-3Δm2<1×10-1eV2 at 90% confidence level. © 2000 The American Physical Society.

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  • Measurement of the solar neutrino energy spectrum using neutrino-electron scattering

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, S. Mine, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, K. Miyano, H. Okazawa, C. Saji, M. Takahata, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto

    Physical Review Letters   82 ( 12 ) 2430 - 2434  1999

     View Summary

    A measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super-Kamiokande detector is presented. The results shown here were obtained from 504 days of data taken between 31 May 1996 and 25 March 1998. The shape of the measured spectrum is compared with the expectation for solar 8B neutrinos. The comparison takes into account both kinematic and detector related effects in the measurement process. The spectral shape comparison between the observation and the expectation gives a χ2 of 25.3 with 15 degrees of freedom, corresponding to a 4.6% confidence level. © 1998 The American Physical Society.

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  • Search for proton decay through p → ¯νK+ in a large water cherenkov detector

    Y. Hayato, M. Earl, Y. Fukuda, T. Hayakawa, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Takeuchi, Y. Totsuka, S. Yamada, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, M. Kirisawa, S. Inaba, K. Miyano, H. Okazawa, C. Saji, M. Takahashi, M. Takahata, K. Higuchi, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto

    Physical Review Letters   83 ( 8 ) 1529 - 1533  1999

     View Summary

    We present results of a search for proton decays, p → ¯νK+, using data from a 33kt?yr exposure of the Super-Kamiokande detector. Two decay modes of the kaon, K+ → µ+νµ and K+ → π+π0, were studied. The data were consistent with the background expected from atmospheric neutrinos; therefore a lower limit on the partial lifetime of the proton τ/B(p → ¯νK+) was found to be 6.7 × 1032 years at 90% confidence level. © 1999 The American Physical Society.

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  • Measurement of radon concentrations at Super-Kamiokande

    Y. Takeuchi, K. Okumura, T. Kajita, S. Tasaka, M. Nemoto, Y. Fukuda, H. Okazawa, T. Hayakawa, K. Ishihara, H. Ishino, Y. Itow, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, Y. Obayashi, A. Okada, N. Sakurai, M. Shiozawa, Y. Suzuki, H. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, D. Casper, W. Gajewski, W. R. Kropp, S. Mine, L. R. Price, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, C. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, M. Kirisawa, S. Inaba, K. Miyano, C. Saji, M. Takahashi, M. Takahata, K. Higuchi, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, A. Hasegawa, T. Hasegawa, S. Hatakeyama, K. Inoue

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   452 ( 3-4 ) 418 - 424  1999

     View Summary

    Radioactivity from radon is a major background for observing solar neutrinos at Super-Kamiokande. In this paper, we describe the measurement of radon concentrations at Super-Kamiokande, the method of radon reduction, and the radon monitoring system. The measurement shows that the current low-energy event rate between 5.0 MeV and 6.5 MeV implies a radon concentration in the Super-Kamiokande water of less than 1.4 mBq/m3. © 1999 Published by Elsevier Science B.V. All rights reserved.

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  • Measurements of the solar neutrino flux from super-Kamiokande's first 300 days (vol 81, pg 1158, 1998)

    Y Fukuda, T Hayakawa, E Ichihara, K Inoue, K Ishihara, H Ishino, Y Itow, T Kajita, J Kameda, S Kasuga, K Kobayashi, Y Kobayashi, Y Koshio, K Martens, M Miura, M Nakahata, S Nakayama, A Okada, M Oketa, K Okumura, M Ota, N Sakurai, M Shiozawa, Y Suzuki, Y Takeuchi, Y Totsuka, S Yamada, M Earl, A Habig, JT Hong, E Kearns, SB Kim, M Masuzawa, MD Messier, K Scholberg, JL Stone, LR Sulak, CW Walter, M Goldhaber, T Barszczak, W Gajewski, PG Halverson, J Hsu, WR Kropp, LR Price, F Reines, HW Sobel, MR Vagins, KS Ganezer, WE Keig, RW Ellsworth, S Tasaka, JW Flanagan, A Kibayashi, JG Learned, S Matsuno, Stenger, V, D Takemori, T Ishii, J Kanzaki, T Kobayashi, K Nakamura, K Nishikawa, Y Oyama, A Sakai, M Sakuda, O Sasaki, S Echigo, M Kohama, AT Suzuki, TJ Haines, E Blaufuss, R Sanford, R Svoboda, ML Chen, Z Conner, JA Goodman, GW Sullivan, M Mori, J Hill, CK Jung, C Mauger, C McGrew, E Sharkey, B Viren, C Yanagisawa, W Doki, T Ishizuka, Y Kitaguchi, H Koga, K Miyano, H Okazawa, C Saji, M Takahata, A Kusano, Y Nagashima, M Takita, T Yamaguchi, M Yoshida, M Etoh, K Fujita, A Hasegawa, T Hasegawa, S Hatakeyama, T Iwamoto, T Kinebuchi, M Koga, T Maruyama, H Ogawa, A Suzuki, F Tsushima, M Koshiba, M Nemoto, K Nishijima, T Futagami, Y Hayato, Y Kanaya, K Kaneyuki, Y Watanabe, D Kielczewska, R Doyle, J George, A Stachyra, L Wai, J Wilkes, K Young

    PHYSICAL REVIEW LETTERS   81 ( 19 ) 4279 - 4279  1998.11  [Refereed]

    DOI

  • Study of the atmospheric neutrino flux in the multi-GeV energy range

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, K. Martens, M. Miura, M. Nakahata, S. Nakayama, A. Okada, M. Oketa, K. Okumura, M. Ota, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, S. B. Kim, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, Z. Conner, J. A. Goodman, G. W. Sullivan, M. Mori, J. Hill, C. K. Jung, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, T. Ishizuka, Y. Kitaguchi, H. Koga, K. Miyano, H. Okazawa, C. Saji, M. Takahata, A. Kusano, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, M. Etoh, K. Fujita, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   436 ( 1-2 ) 33 - 41  1998.09

     View Summary

    The flavor ratio of the atmospheric neutrino flux and its zenith angle dependence have been studied in the multi-GeV energy range using an exposure of 25.5 kiloton-years of the Super-Kamiokande detector. By comparing the data to a detailed Monte Carlo simulation, the ratio (μ/e)DATA/(μ/e)MC was measured to be 0.66 ± 0.06(stat.) ± 0.08(sys.). In addition, a strong distortion in the shape of the μ-like event zenith angle distribution was observed. The ratio of the number of upward to downward μ-like events was found to be 0.52+0.070.06(stat.) ± 0.01(sys.), with an expected value of 0.98 ± 0.03(stat.) ± 0.02(sys.), while the same ratio for the e-like events was consistent with unity. © 1998 Elsevier Science B.V. All rights reserved.

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  • Measurement of a small atmospheric ν<inf>μ</inf>/ν<inf>e</inf> ratio

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, K. Martens, M. Miura, M. Nakahata, S. Nakayama, A. Okada, M. Oketa, K. Okumura, M. Ota, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, J. T. Hong, E. Kearns, S. B. Kim, M. Masuzawa, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, M. Mori, F. Goebel, J. Hill, C. K. Jung, C. Mauger, C. McGrew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, T. Ishizuka, Y. Kitaguchi, H. Koga, K. Miyano, H. Okazawa, C. Saji, M. Takahata, A. Kusano, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   433 ( 1-2 ) 9 - 18  1998.08

     View Summary

    From an exposure of 25.5 kiloton-years of the Super-Kamiokande detector, 900 muon-like and 983 electron-like single-ring atmospheric neutrino interactions were detected with momentum pe > 100 MeV/c, pμ > 200 MeV/c, and with visible energy less than 1.33 GeV. Using a detailed Monte Carlo simulation, the ratio (μ/e)DATA/(μ/e)MC was measured to be 0.61 ± 0.03(stat.) ± 0.05(sys.), consistent with previous results from the Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from theoretical models of atmospheric neutrino production. © 1998 Published by Elsevier Science B.V. All rights reserved.

    DOI

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    567
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  • Spin excitations by C-12((p)over-right-arrow,(p)over-right-arrow(1)) reactions at theta=0 degrees

    A Tamii, T Ishikawa, M Itoh, T Kawabata, M Nakamura, H Sakaguchi, H Takeda, T Taki, M Yosoi, H Akimune, Daito, I, M Fujiwara, K Hatanaka, F Ihara, K Ishibashi, T Inomata, T Noro, E Obayashi, H Yoshida, M Yoshimura, Y Fujita, H Toyokawa, K Hosono, M Kawabata

    INTERNATIONAL SYMPOSIUM ON NEW FACET OF SPIN GIANT RESONANCES IN NUCLEI     424 - 433  1998  [Refereed]

     View Summary

    We measured a complete set of polarization transfer observables in C-12 ((p) over right arrow,(p) over right arrow') reactions at theta = 0 degrees. D-LL for the excitation of the 1(+), T = 0 state at 12.7 MeV resulted in a large value of 0.7. It is considered to be due to interference of the isovector tensor interaction and the isoscalar central spin-dependent interaction. Distorted wave impulse approximation (DWIA) calculations using the Franey and Love effective interaction predicts a large value for D-LL but it fails to reproduce both D-NN and D-LL simultaneously. For the 1(+), T = 1 state at 15.1 MeV they are reproduced simultaneously by reducing the strength of the isovector tensor interaction. Large D-LL values are also predicted for other isoscalar spin excitations and it was confirmed for prominent isoscalar strengths.

  • A Pb-SciFi imaging calorimeter for high energy cosmic electrons

    S Torii, N Tateyama, T Tamura, K Yoshida, T Yamagami, H Murakami, T Kobayashi, T Yuda, J Nishimura

    SCIFI 97: CONFERENCE ON SCINTILLATING FIBER DETECTORS   450   578 - 585  1998  [Refereed]

     View Summary

    The BETS (balloon-borne electron telescope with scintillating fiber) detector has been developed for high-altitude balloon flights to observe high-energy cosmic-electrons. The detector consists of an imaging calorimeter and a trigger system for particle identification and energy measurement. The calorimeter is composed of scintillating fibers and leads of a rotal thickness of similar to 8 r.l. Two sets of an image-intensifier and CCD camera system are adopted for read-out of 10,080 scintillating fibers. The accelerator tests were carried out to study performance of the detector by the CERN-SPS electron and proton beams. It is demonstrated in the flight data that a reliable identification of the electron component has been successfully achieved up to 100 GeV, and the energy spectrum has been measured.

  • Measurements of the solar neutrino flux from super-kamiokande’s first 300 days

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, K. Martens, M. Miura, M. Nakahata, S. Nakayama, A. Okada, M. Oketa, K. Okumura, M. Ota, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, J. T. Hong, E. Kearns, S. B. Kim, M. Masuzawa, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, M. Mori, J. Hill, C. K. Jung, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, T. Ishizuka, Y. Kitaguchi, H. Koga, K. Miyano, H. Okazawa, C. Saji, M. Takahata, A. Kusano, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, M. Etoh

    Physical Review Letters   81 ( 6 ) 1158 - 1162  1998

     View Summary

    The first results of the solar neutrino flux measurement from Super-Kamiokande are presented. The results shown here are obtained from data taken between 31 May 1996, and 23 June 1997. Using our measurement of recoil electrons with energies above 6.5 MeV, we infer the total flux of 8B solar neutrinos to be 2.42±0.06(stat)+0.10-0.07(syst)×106cm-2s-1. This result is consistent with the Kamiokande measurement and is 36% of the flux predicted by the BP95 solar model. The flux is also measured in 1.5 month subsets and shown to be consistent with a constant rate. © 1998 The American Physical Society.

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  • Evidence for oscillation of atmospheric neutrinos

    Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, A. Okada, K. Okumura, N. Sakurai, M. Shiozawa, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczxak, D. Casper, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, M. Smy, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. J. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, S. Mine, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, B. K. Kim, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, B. Viren, C. Yanagisawa, W. Doki, K. Miyano, H. Okazawa, C. Saji, M. Takahata, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa, T. Hasegawa, S. Hatakeyama, T. Iwamoto

    Physical Review Letters   81 ( 8 ) 1562 - 1567  1998

     View Summary

    We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor νμ↔ντ oscillations with sin22θ>0.82 and 5×10−4<Δm2<6×10−3eV2 at 90% confidence level. © 1998 The American Physical Society.

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    4578
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  • Search for proton decay via p→e+π0 in a large water cherenkov detector

    M. Shiozawa, B. Viren, Y. Fukuda, T. Hayakawa, E. Ichihara, K. Inoue, K. Ishihara, H. Ishino, Y. Itow, T. Kajita, J. Kameda, S. Kasuga, K. Kobayashi, Y. Kobayashi, Y. Koshio, M. Miura, M. Nakahata, S. Nakayama, A. Okada, M. Oketa, K. Okumura, M. Ota, N. Sakurai, Y. Suzuki, Y. Takeuchi, Y. Totsuka, S. Yamada, M. Earl, A. Habig, E. Kearns, M. D. Messier, K. Scholberg, J. L. Stone, L. R. Sulak, C. W. Walter, M. Goldhaber, T. Barszczak, W. Gajewski, P. G. Halverson, J. Hsu, W. R. Kropp, L. R. Price, F. Reines, H. W. Sobel, M. R. Vagins, K. S. Ganezer, W. E. Keig, R. W. Ellsworth, S. Tasaka, J. W. Flanagan, A. Kibayashi, J. G. Learned, S. Matsuno, V. Stenger, D. Takemori, T. Ishii, J. Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Y. Oyama, A. Sakai, M. Sakuda, O. Sasaki, S. Echigo, M. Kohama, A. T. Suzuki, T. J. Haines, E. Blaufuss, R. Sanford, R. Svoboda, M. L. Chen, Z. Conner, J. A. Goodman, G. W. Sullivan, M. Mori, J. Hill, C. K. Jung, K. Martens, C. Mauger, C. Mc Grew, E. Sharkey, C. Yanagisawa, W. Doki, T. Ishizuka, Y. Kitaguchi, H. Koga, K. Miyano, H. Okazawa, C. Saji, M. Takahata, A. Kusano, Y. Nagashima, M. Takita, T. Yamaguchi, M. Yoshida, S. B. Kim, M. Etoh, K. Fujita, A. Hasegawa

    Physical Review Letters   81 ( 16 ) 3319 - 3323  1998

     View Summary

    We have searched for proton decay via p→e+π0 using data from a 25.5ktonyr exposure of the Super-Kamiokande detector. We find no candidate events with an expected background induced by atmospheric neutrinos of 0.1 events. From these data, we set a lower limit on the partial lifetime of the proton τ/Bp→e+π0 to be 1.6×1033years at a 90% confidence level. © 1998 The American Physical Society.

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Research Projects

  • Development of new techniques for next generation of dark matter search detectors

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2017.04
    -
    2020.03
     

    Kobayashi Kazuyoshi

     View Summary

    Mechanism of 210Pb accumulation on surface of material was understood better and The prospect of an end to the survey was seen for no accumulation using area neutralization system. Also, the prospect of an end to the survey was seen for sensitivity improvement of radon concentration using the electrostatic collection type radon detector.

  • A large-scale darkmatter direct-detection experiment

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2014.07
    -
    2019.03
     

    KISHIMOTO Yasuhiro, ABE Ko, SUZUKI Yoichiro

     View Summary

    In order to address to one of the biggest mysteries in the universe, the dark matter, this research project has challenged two tasks: dark matter search with a large-scale experimental apparatus, and development and research of a next-generation dark matter search apparatus.
    As for the first subject, in this study, we searched for the seasonal modulation signal by dark matter, which the previous research (DAMA / LIBRA) claims, and denied the result. In addition, we searched for dark matter candidates called Bosonic-Super WIMPs, and for the first time published the conclusion that "the vector type cannot be the main component of dark matter". For the second issue, we developed and improved ultra-low background technology.

  • A Search for Dark Matter

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2012.04
    -
    2015.03
     

    SUZUKI Yoichiro, MORIYAMA Shigetaka, NAKAHATA Masayuki, KISHIMOTO Yasuhiro, YAMASHITA Masaki, MARTENS Kai, TAKEDA Atsushi, ABE Kou, SEKIYA Hiroyuki, OGAWA Hiroshi, KOBAYASHI Kazuyoshi, HIRAIDE Katsuki, LIU Jing, YANG Byeongsu, NAKAMURA Shogo, NISHIJIMA Kyoji, ITOW Yoshitaka, MASUDA Kimiaki, TAKEUCHI Yasuo, MIUCHI Kentaro, FUKUDA Yoshiyuki, TASAKA Shigeki

     View Summary

    We know that there exists unknown matter in the universe called dark matter that amounts 5 to 6 times more than the ordinary matter. However, we do not know what they are. There are varieties of candidates for dark matter. Some interact with the ordinary matter and kick out the nucleus and some emit gamma rays when they hit the target material of the detector. Our detector, using 835 kg of liquid xenon as a target material has a characteristics of having very low energy threshold and the ability to detect e/gamma events as well as nuclear recoils. Therefore we are able to make high sensitive searches for low mass dark matter and a new type of dark matter that emits gamma rays. After the observation lasted more than one year, we could not find dark matter, but set very stringent limits for those candidates. We have also demonstrated that we are able to make the detector bigger and be able to achieve much higher sensitive searches in future.

  • Study of Dark Matter

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2007
    -
    2011
     

    SUZUKI Yoichiro, MORIYAMA Shigetaka, NAKAHATA Masayuki, KOSHIO Yuusuke, NAKAMURA Syogo, TAKEUCHI Yasuo, KISIMOTO Yasuhiro, TAKEDA Atsushi, ABE Kou, SEKIYA Hiroyuki, YAMASHITA Masaki, OGAWA Hiroshi, KOBAYASHI Kazuyoshi, HIRAIDE Katsuki

     View Summary

    We have succeeded to construct the world largest liquid Xenon detector in order to make an observation of Dark Matter in the laboratory experiment. By the calibration data to understand the detector revealed that we have large light yields which shows the high sensitivity for the dark matter search. We have also succeeded to reduce the most serious background of Kr to the level of 2. 7 ppt which is the world lowest background level achieved. The most of the source of backgrounds are identified and we are ready to make an observation.

  • Development of scattering and absorption length monitor system in liquid xenon in dark matter experiment

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2008
    -
    2009
     

    KOBAYASHI Kazuyoshi

     View Summary

    In recent dark mater search experiments, liquid Xenon is being used. Because scintillation vacuum ultra violet light is used in the dark matter experiments, property of the light in the liquid xenon is getting important. In this research, monitoring system of scattering and absorption length in liquid xenon was developed.

Misc

  • Distillation of liquid xenon to remove krypton

    K. Abe, J. Hosaka, T. Iida, M. Ikeda, K. Kobayashi, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, Y. Nakajima, T. Namba, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, K. Ueshima, M. Yamashita, K. Kaneyuki, Y. Ebizuka, J. Kikuchi, A. Ota, S. Suzuki, T. Takahashi, H. Hagiwara, T. Kamei, K. Miyamoto, T. Nagase, S. Nakamura, Y. Ozaki, T. Sato, Y. Fukuda, T. Sato, K. Nishijima, M. Sakurai, T. Maruyama, D. Motoki, Y. Itow, H. Ohsumi, S. Tasaka, S. B. Kim, Y. D. Kim, J. I. Lee, S. H. Moon, Y. Urakawa, M. Uchino, Y. Kamioka

    ASTROPARTICLE PHYSICS   31 ( 4 ) 290 - 296  2009.05

     View Summary

    A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = similar to 3 x 10(-12) was achieved. This development is crucial in facilitating high-sensitivity low-background experiments such as the search for dark matter in the universe. (C) 2009 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Scintillation yield of liquid xenon at room temperature

    K. Ueshima, K. Abe, T. Iida, M. Ikeda, K. Kobayashi, Y. Koshio, A. Minamino, M. Miura, S. Moriyama, M. Nakahata, Y. Nakajima, H. Ogawa, H. Sekiya, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takeuchi, M. Yamashita, K. Kaneyuki, T. Doke, Y. Ebizuka, J. Kikuchi, A. Ota, S. Suzuki, T. Takahashi, H. Hagiwara, T. Kamei, K. Miyamoto, T. Nagase, S. Nakamura, Y. Ozaki, T. Sato, Y. Fukuda, T. Sato, K. Nishijima, M. Sakurai, T. Maruyama, D. Motoki, Y. Itow, H. Ohsumi, S. Tasaka, S. B. Kim, Y. D. Kim, J. I. Lee, S. H. Moon

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   594 ( 2 ) 148 - 154  2008.09

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    The intensity of scintillation light emission from liquid xenon at room temperature was measured. The scintillation light yield at 1 degrees C was measured to be 0.64 +/- 0.02 (stat.) +/- 0.06 (sys.) of that at -100 degrees C. Using the reported light yield at -100 degrees C (46 photons/keV), the measured light yield at 1 degrees C corresponds to 29 photons/keV. This result shows that liquid xenon scintillator provides high light yield even at room temperature. (C) 2008 Elsevier B.V. All rights reserved.

    DOI J-GLOBAL

  • Isoscalar giant dipole resonance in Pb-208 via inelastic alpha scattering at 400 MeV and nuclear incompressibility

    M Uchida, H Sakaguchi, M Itoh, M Yosoi, T Kawabata, H Takeda, Y Yasuda, T Murakami, T Ishikawa, T Taki, N Tsukahara, S Terashima, U Garg, M Hedden, B Kharraja, M Koss, BK Nayak, S Zhu, M Fujiwara, H Fujimura, K Hara, E Obayashi, HP Yoshida, H Akimune, MN Harakeh, M Volkerts

    PHYSICS LETTERS B   557 ( 1-2 ) 12 - 19  2003.03

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    The isoscalar giant dipole resonance (ISGDR) in Pb-208 has been investigated with inelastic a-scattering of 400 MeV at extremely forward angles, including 0degrees. Energy spectra, virtually free from instrumental background, have been obtained and the ISGDR strength distribution has been extracted using a multipole-decomposition analysis (MDA). A difference-of-spectra approach yields the same ISGDR centroid energy as with MDA. These results lead to a value for nuclear incompressibility that is consistent for both the isoscalar dipole and monopole modes. (C) 2003 Elsevier Science B.V All rights reserved.

    DOI

  • Structure and decay of the s-hole state in B-11 studied via the C-12(p, 2p)B-11* reaction

    M Yosoi, H Akimune, Daito, I, H Eijiri, H Fujimura, M Fujiwara, T Ishikawa, M Itoh, T Kawabata, M Nakamura, T Noro, E Obayashi, H Sakaguchi, H Takeda, T Taki, A Tami, H Toyokawa, N Tsukahara, M Uchida, T Yamada, HP Yoshida

    PHYSICS LETTERS B   551 ( 3-4 ) 255 - 261  2003.01

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    Charged particle decay of the s-hole state in B-11 was measured in coincidence with the quasifree C-12(p, 2p) reaction at 392 MeV incident energy. Triton-decay was found to be dominant despite its smaller Q-value than that of a-decay. The measured decay pattern is compared to the results of statistical model and microscopic SU(3)-cluster model calculations. The energy spectrum around the s-hole state exhibits three bump-like structures, which can be qualitatively explained by a recent shell-model calculation. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI

  • Polarization transfer in the O-16(p,p ') reaction at forward angles and structure of the spin-dipole resonances

    T Kawabata, T Ishikawa, M Itoh, M Nakamura, H Sakaguchi, H Takeda, T Taki, M Uchida, Y Yasuda, M Yosoi, H Akimune, K Yamasaki, GPA Berg, H Fujimura, K Hara, K Hatanaka, J Kamiya, T Noro, E Obayashi, T Wakasa, HP Yoshida, BA Brown, H Fujita, Y Fujita, Y Shimbara, H Ueno, M Fujiwara, K Hosono, A Tamii, H Toyokawa

    PHYSICAL REVIEW C   65 ( 6 )  2002.06

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    Cross sections and polarization transfer observables in the O-16(p,p') reactions at 392 MeV were measured at several angles between theta(lab)=0degrees and 14degrees. The non-spin-flip (DeltaS=0) and spin-flip (DeltaS=1) strengths in transitions to several discrete states and broad resonances in O-16 were extracted using a model-independent method. The giant resonances in the energy region of E-x=19-27 MeV were found to be predominantly excited by DeltaL=1 transitions. The strength distribution of spin-dipole transitions with DeltaS=1 and DeltaL=1 were deduced. The obtained distribution was compared with a recent shell model calculation. Experimental results are reasonably explained by distorted-wave impulse-approximation calculations with the shell model wave functions.

    DOI

  • Study of Giant Monopole Resonance in Ni-58 via the ((p)over-right-arrow, (p)over-right-arrow &apos;) reaction at 0 degrees

    T Ishikawa, H Akimune, Daito, I, H Fujimura, Y Fujita, M Fujiwara, K Hatanaka, K Hosono, F Ihara, M Itoh, T Kawabata, M Nakamura, T Noro, E Obayashi, H Sakaguchi, A Tamii, H Takeda, T Taki, H Toyokawa, HP Yoshida, M Yoshimura, M Yosoi

    NUCLEAR PHYSICS A   687 ( 1-2 ) 58C - 63C  2001.04

  • Giant monopole resonances in deformed nuclei

    M Itoh, H Sakaguchi, T Ishikawa, T Kawabata, T Murakami, H Takeda, T Taki, N Tukaharaa, M Uchida, Y Yasuda, H Fujimura, K Hara, T Noro, E Obayashi, HP Yoshida, M Yosoi, M Fujiwara, P Boutachkov, U Garg, B Kharraja, M Volkerts

    NUCLEAR PHYSICS A   687 ( 1-2 ) 52C - 57C  2001.04

  • Thin ice target for O-16(p,p ') experiment

    T Kawabata, H Akimune, H Fujimura, H Fujita, Y Fujita, M Fujiwara, K Hara, K Hatanaka, K Hosono, T Ishikawa, M Itoh, J Kamiya, M Nakamura, T Noro, E Obayashi, H Sakaguchi, Y Shimbara, H Takeda, T Taki, A Tamii, H Toyokawa, N Tsukahara, M Uchida, H Ueno, T Wakasa, K Yamasaki, Y Yasuda, HP Yoshida, M Yosoi

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   459 ( 1-2 ) 171 - 176  2001.02

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    A windowless and self-supporting ice target is described. An ice sheet with a thickness of 29.7 mg/cm(2) cooled by liquid nitrogen was placed at the target position of a magnetic spectrometer and worked stably in the O-16(p,p') experiment at E-p = 392 MeV. Background-free spectra were obtained. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI

  • Polarization transfer observables for proton inelastic scattering from 12C at 0°

    A. Tamii, H. Akimune, I. Daito, Y. Fujita, M. Fujiwara, K. Hatanaka, K. Hosono, F. Ihara, T. Inomata, T. Ishikawa, M. Itoh, M. Kawabata, T. Kawabata, M. Nakamura, T. Noro, E. Obayashi, H. Sakaguchi, H. Takeda, T. Taki, H. Toyokawa, H. P. Yoshida, M. Yoshimura, M. Yosoi

    Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics   459 ( 1-3 ) 61 - 66  1999

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    Polarization transfer (PT) observables in the 12C(p,p′) reaction at 0° for 392 MeV protons have been measured. The excitation strengths are decomposed into the spin-flip part and the non-spin-flip part by using the obtained PT observables. The PT observables for excitation of the 1+, T = 0 and 1+, T = 1 states are compared with distorted wave impulse approximation calculations. The strength ratios of the isoscalar spin-dependent term to the isovector tensor term and the isovector tensor term to the isovector spin-dependent term are reasonably consistent with the Franey and Love interaction. © 1999 Published by Elsevier Science B.V. All rights reserved.

    DOI

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