Publications [#248770] of Christopher Walter

Papers Published
  1. Fechner, M; Abe, K; Hayato, Y; Iida, T; Ikeda, M; Kameda, J; Kobayashi, K; Koshio, Y; Miura, M; Moriyama, S; Nakahata, M; Nakayama, S; Obayashi, Y; Ogawa, H; Sekiya, H; Shiozawa, M; Suzuki, Y; Takeda, A; Takenaga, Y; Takeuchi, Y; Ueno, K; Ueshima, K; Watanabe, H; Yamada, S; Hazama, S; Higuchi, I; Ishihara, C; Kajita, T; Kaneyuki, K; Mitsuka, G; Nishino, H; Okumura, K; Tanimoto, N; Vagins, MR; Dufour, F; Kearns, E; Litos, M; Raaf, JL; Stone, JL; Sulak, LR; Wang, W; Goldhaber, M; Dazeley, S et al., Kinematic reconstruction of atmospheric neutrino events in a large water Cherenkov detector with proton identification, Physical Review D - Particles, Fields, Gravitation, and Cosmology, vol. 79 no. 11 (2009), pp. 112010 [pdf], [doi] .

    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. © 2009 The American Physical Society.