Measurement of neutrino oscillation with KamLAND: Evidence of spectral distortion

T. Araki, K. Eguchi, S. Enomoto, K. Furuno, K. Ichimura, H. Ikeda, K. Inoue, K. Ishihara, T. Iwamoto, T. Kawashima, Y. Kishimoto, M. Koga, Y. Koseki, T. Maeda, T. Mitsui, M. Motoki, K. Nakajima, H. Ogawa, K. Owada, J. S. RicolI. Shimizu, J. Shirai, F. Suekane, A. Suzuki, K. Tada, O. Tajima, K. Tamae, Y. Tsuda, H. Watanabe, J. Busenitz, T. Classen, Z. Djurcic, G. Keefer, K. McKinny, D. M. Mei, A. Piepke, E. Yakushev, B. E. Berger, Y. D. Chan, M. P. Decowski, D. A. Dwyer, S. J. Freedman, Y. Fu, B. K. Fujikawa, J. Goldman, F. Gray, K. M. Heeger, K. T. Lesko, K. B. Luk, H. Murayama, A. W.P. Poon, H. M. Steiner, L. A. Winslow, G. A. Horton-Smith, C. Mauger, R. D. McKeown, P. Vogel, C. E. Lane, T. Miletic, P. W. Gorham, G. Guillian, J. G. Learned, J. Maricic, S. Matsuno, S. Pakvasa, S. Dazeley, S. Hatakeyama, A. Rojas, R. Svoboda, B. D. Dieterle, J. Detwiler, G. Gratta, K. Ishii, N. Tolich, Y. Uchida, M. Batygov, W. Bugg, Y. Efremenko, Y. Kamyshkov, A. Kozlov, Y. Nakamura, C. R. Gould, H. J. Karwowski, D. M. Markoff, J. A. Messimore, K. Nakamura, R. M. Rohm, W. Tornow, R. Wendell, A. R. Young, M. J. Chen, Y. F. Wang, F. Piquemal

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We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 ν̄e candidate events with energies above 3.4 MeV compared to 365.2 ± 23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8 ± 7.3 expected background events, the statistical significance for reactor ν̄e disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from ν̄e oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Δm2 = 7.9 +0.5+0.6 × 10-5 eV2. A global analysis of data from KamLAND and solar-neutrino experiments yields Δm2 = × 10-5 eV2 and tan2θ = 0.400.07+0.10 the most precise determination to date.

Original languageEnglish
Article number081801
JournalPhysical review letters
Issue number8
Publication statusPublished - 2005 Mar 4

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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