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• Sensitivity of the Hyper-Kamiokande experiment to neutrino oscillation parameters using accelerator neutrinos

  Zsoldos S., Zito M., Zietara K., Ziembicki M., Zhu T., Zhong H., Zhao X., Zarnecki G., Zaremba K., Zalipska J., Zaldivar B., Yuriy O., Yu T., Yu I., Yousefnejad S., Yoshioka Y., Yoshimoto Y., Yoshida T., Yoo J., Yokoyama M., Yevarouskaya U., Yershov N., Yano T., Yang B.S., Yamauchi K., Yamashita M., Yamamoto K., Yamaguchi Y., Xie Z., Xia J., Wuethrich J., Wronka S., Wojciechowski M., Wilson S., Wilson J.R., Wendell R., Wark D., Wachala T., Vyalkov M., Vogelaar R., Vladisavljevic T., Vivolo D., Virginet U., Vinning B., Vasseur G., Vallmajó O., Valder S., Vagins M., Urquijo P., Urano S., Uchida Y., Tzanov M., Tsushima T., Tsukamoto T., Tsui K.M., Tsuchii R., Tseng J., Tran N., Tomiya T., Tomatani Sánchez A.K., Toledo Alarcón J.F., Tiwari D., Thrane E., Thiesse M., Terada K., Tashiro T., Tanigawa H., Tanaka M., Tanaka H.K.M., Tanaka H., Takhistov V., Takeuchi Y., Taketa A., Takemoto Y., Takeda A., Taghayor S., Tada M., Svirida D., Suzuki Y., Suzuki S.Y., Suzuki A., Suwa Y., Sunanda , Suchenek M., Suárez Gómez S.L., Studenikin A., Stowell P., Stawarz L., Stavropoulos D., Stankevich K., Spradlin P., Spisso B., Spina R., Sozzi M.S., Soler F.J.P., Sobel H.W., Sobczyk J., Smy M., Smithers B.R., Skwarczynski K.

  European Physical Journal C 86 （ 2 ）  2026年02月

  ISSN  14346044

  　概要を見る

  This paper presents the expected sensitivity to the neutrino oscillation parameters of the Hyper-Kamiokande long-baseline program. The Hyper-Kamiokande experiment, currently under construction in Japan, will measure the oscillations of accelerator-produced neutrinos with thousands of selected events per sample: this corresponds to an increase of statistics of a factor 25–100 with respect to recent results from the currently-running long-baseline neutrino oscillation experiment in Japan, T2K. In the most favorable scenario we will achieve the discovery of Charge-Parity (CP) violation in neutrino oscillation at 5σ C.L. in less than 3 years. With 10 years of data-taking, and assuming a neutrino : antineutrino beam running ratio of 1:3, a CP violation discovery at 5σ C.L. is possible for more than 60% of the actual values of the CP-violating phase, δCP. Moreover, we will measure δCP with a precision ranging from 20∘, in the case of maximal CP violation, to 6∘, in the case of CP conservation. We aim to achieve a 0.5% resolution on the Δm322 parameter, and a resolution between 3% and 0.5% on the sin2θ23 parameter, depending on its true value. These results are obtained by extending the analysis methods of T2K with dedicated tuning to take into account the Hyper-Kamiokande design: the larger far detector, the more powerful beam, the upgraded near detector ND280, and the planned additional Intermediate Water Cherenkov Detector.

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• Impact of external radiation on dark rate noise measurement for the Hyper-Kamiokande photomultiplier tube

  Mandokoro Y., Bronner C., Ishitsuka M., Tashiro T., Nishimura Y.

  Journal of Instrumentation 20 （ 5 ）  2025年05月

  　概要を見る

  The Hyper-Kamiokande (HK) is a next-generation water Cherenkov detector currently under construction in Japan as of 2025, and scheduled to begin operation in 2027. A new PMT has been developed for HK with improvements in detection efficiency, timing resolution, and pressure tolerance by a factor of two with respect to those used in the Super-Kamiokande detector. The HK detector will be instrumented with 20,000 photomultiplier tubes (PMT). Currently, the PMTs are produced, and the performance testing of the delivered PMTs is underway in parallel. In this test, it was observed that the dark rate values differed depending on the measurement location. The difference is considered due to environmental radiation, and we have conducted measurements of dark rate variations with radiation sources. We measured correlations between the irradiation of γ rays and dark noise rate and the evaluated intrinsic dark noise rate of HK PMT after subtracting the contribution due to environmental radiation.

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• Optimization of geomagnetic shielding based on detection efficiency

  Cabo S.R., Nishimura Y., Gómez S.L.S., Bonavera L., Sanchez M.L., Santos J.D., de Cos F.J.

  European Physical Journal Plus 140 （ 4 ）  2025年04月

  　概要を見る

  Due to the progressive increase in size of the latest Cherenkov-type detectors, it is becoming increasingly important to design a suitable compensation system based on coils of the Earth’s magnetic field to ensure the correct operation of the photomultipliers (PMTs). Until now, most studies have assessed the correct functioning of such a system by the proportion of PMTs experiencing more than 100 mG of magnetic field perpendicular to their axis. In the present study, we discuss whether this evaluation parameter is the most appropriate and propose the average residual perpendicular magnetic field <Bperp> as an alternative that more closely reflects the loss of detection efficiency of PMTs. A compensation system design is also proposed that offers good results as well as being economical to optimize this parameter.

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• First Joint Oscillation Analysis of Super-Kamiokande Atmospheric and T2K Accelerator Neutrino Data

  Abe K., Abe S., Bronner C., Hayato Y., Hiraide K., Hosokawa K., Ieki K., Ikeda M., Kameda J., Kanemura Y., Kaneshima R., Kashiwagi Y., Kataoka Y., Miki S., Mine S., Miura M., Moriyama S., Nakahata M., Nakano Y., Nakayama S., Noguchi Y., Sato K., Sekiya H., Shiba H., Shimizu K., Shiozawa M., Sonoda Y., Suzuki Y., Takeda A., Takemoto Y., Tanaka H., Yano T., Han S., Kajita T., Okumura K., Tashiro T., Tomiya T., Wang X., Yoshida S., Fernandez P., Labarga L., Ospina N., Zaldivar B., Pointon B.W., Kearns E., Mirabito J., Raaf J.L., Wan L., Wester T., Bian J., Griskevich N.J., Smy M.B., Sobel H.W., Takhistov V., Yankelevich A., Hill J., Jang M.C., Lee S.H., Moon D.H., Park R.G., Bodur B., Scholberg K., Walter C.W., Beauchêne A., Drapier O., Giampaolo A., Mueller T.A., Santos A.D., Paganini P., Quilain B., Rogly R., Nakamura T., Jang J.S., MacHado L.N., Learned J.G., Choi K., Iovine N., Cao S., Anthony L.H.V., Martin D., Prouse N.W., Scott M., Uchida Y., Berardi V., Calabria N.F., Catanesi M.G., Radicioni E., Langella A., De Rosa G., Collazuol G., Feltre M., Iacob F., Mattiazzi M., Ludovici L., Gonin M., Périssé L., Pronost G., Fujisawa C., Horiuchi S., Kobayashi M.

  Physical Review Letters 134 （ 1 ）  2025年01月

  ISSN  00319007

  　概要を見る

  The Super-Kamiokande and T2K Collaborations present a joint measurement of neutrino oscillation parameters from their atmospheric and beam neutrino data. It uses a common interaction model for events overlapping in neutrino energy and correlated detector systematic uncertainties between the two datasets, which are found to be compatible. Using 3244.4 days of atmospheric data and a beam exposure of 19.7(16.3)×1020 protons on target in (anti)neutrino mode, the analysis finds a 1.9σ exclusion of CP conservation (defined as JCP=0) and a 1.2σ exclusion of the inverted mass ordering.

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• Search for proton decay via p →e+η and p →μ+η with a 0.37 Mton-year exposure of Super-Kamiokande

  Taniuchi N., Abe K., Abe S., Asaoka Y., Bronner C., Harada M., Hayato Y., Hiraide K., Hosokawa K., Ieki K., Ikeda M., Kameda J., Kanemura Y., Kaneshima R., Kashiwagi Y., Kataoka Y., Miki S., Mine S., Miura M., Moriyama S., Nakahata M., Nakayama S., Noguchi Y., Pronost G., Okamoto K., Sato K., Sekiya H., Shiba H., Shimizu K., Shiozawa M., Sonoda Y., Suzuki Y., Takeda A., Takemoto Y., Takenaka A., Tanaka H., Watanabe S., Yano T., Kajita T., Okumura K., Tashiro T., Tomiya T., Wang X., Yoshida S., Megias G.D., Fernandez P., Labarga L., Ospina N., Zaldivar B., Pointon B.W., Kearns E., Mirabito J., Raaf J.L., Wan L., Wester T., Bian J., Griskevich N.J., Kropp W.R., Locke S., Smy M.B., Sobel H.W., Takhistov V., Yankelevich A., Hill J., Jang M.C., Kim J.Y., Lee S.H., Lim I.T., Moon D.H., Park R.G., Yang B.S., Bodur B., Scholberg K., Walter C.W., Beauchêne A., Bernard L., Coffani A., Drapier O., El Hedri S., Giampaolo A., Mueller T.A., Santos A.D., Paganini P., Rogly R., Nakamura T., Jang J.S., Machado L.N., Learned J.G., Choi K., Iovine N., Cao S., Anthony L.H.V., Martin D., Prouse N.W., Scott M., Sztuc A.A., Uchida Y., Berardi V., Calabria N.F., Catanesi M.G.

  Physical Review D 110 （ 11 ）  2024年12月

  ISSN  24700010

  　概要を見る

  A search for proton decay into e+/μ+ and a η meson has been performed using data from a 0.373 Mton·year exposure (6050.3 live days) of Super-Kamiokande. Compared to previous searches this work introduces an improved model of the intranuclear η interaction cross section, resulting in a factor of 2 reduction in uncertainties from this source and ∼10% increase in signal efficiency. No significant data excess was found above the expected number of atmospheric neutrino background events resulting in no indication of proton decay into either mode. Lower limits on the proton partial lifetime of 1.4×1034 years for p→e+η and 7.3×1033 years for p→μ+η at the 90% CL were set. These limits are around 1.5 times longer than our previous study and are the most stringent to date.

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• 新光検出システム確立で目指す大型ニュートリノ・核子崩壊検出装置の高性能化

  西村, 康宏

  科学研究費補助金研究成果報告書 2021年

• 次期スーパーカミオカンデ実験で始めるニュートリノ宇宙観測技術の基礎研究

  西村, 康宏

  学事振興資金研究成果実績報告書 （慶應義塾大学）  2019年

競争的研究費の研究課題 【 表示 ／ 非表示 】

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• 陽子崩壊の低エネルギー事象高感度探索

  2023年04月

  -

  2026年03月

  西村 康宏, 基盤研究(C), 補助金,  研究代表者

• 新光検出システム確立で目指す大型ニュートリノ・核子崩壊検出装置の高性能化

  2018年04月

  -

  2020年03月

  文部科学省・日本学術振興会, 科学研究費助成事業, 西村　康宏, 若手研究, 補助金,  研究代表者

担当授業科目 【 表示 ／ 非表示 】

担当授業科目 【 表示 ／ 非表示 】

• 先端数物科学修士研究１

  2026年度

• 基礎理工学特別研究第１

  2026年度

• 基礎理工学課題研究

  2026年度

• 卒業研究

  2026年度

• 自然科学実験

  2026年度

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