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. TakeuchiK. 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, K. Nishijima, Y. Yokosawa, M. Koshiba, Y. Totsuka, S. Chen, Y. Heng, Z. Yang, H. Zhang, D. Kielczewska, E. Thrane, R. J. Wilkes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number112010
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume79
Issue number11
DOIs
Publication statusPublished - 2009 Jun 22
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)

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