Updated on 2022/05/22

写真a

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

Education

  • 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

  • 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

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    <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

  • 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

  • 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

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    © 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.

    DOI

  • 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

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    © 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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  • 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

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    © 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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  • 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

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    © 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

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    © 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

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    © 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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  • 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

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    © 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

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    © 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

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    © 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

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    © 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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  • 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

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    © 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.

    DOI

  • Dark matter searches in XMASS

    Kazuyoshi Kobayashi

    Proceedings of Science   340  2019

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    © 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

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    © 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

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    © 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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  • 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

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    © 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 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

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    © 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

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    © 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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  • 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

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    © 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.

    DOI

  • 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

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    © 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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  • 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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  • 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

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    © 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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  • 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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  • 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.

    DOI

  • 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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  • 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.

    DOI

  • 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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  • 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

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    © 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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  • 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

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    © 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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  • 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.

    DOI

  • 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

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    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.

    DOI

  • 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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  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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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  • 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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  • 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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  • 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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  • 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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  • 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.

    DOI

  • 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.

    DOI

  • 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".

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    DOI

  • 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.

    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.

    DOI

  • 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

  • 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

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    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.

    DOI

  • 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

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    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.

    DOI

  • 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

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    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.

    DOI

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