Phys. Rev. Lett.
94,
081801
(2005)
[5 pages]
Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion
T. Araki et al. KamLAND Collaboration
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T. Araki1, K. Eguchi1, S. Enomoto1, K. Furuno1, K. Ichimura1, H. Ikeda1, K. Inoue1, K. Ishihara1,*, T. Iwamoto1,†, T. Kawashima1, Y. Kishimoto1, M. Koga1, Y. Koseki1, T. Maeda1, T. Mitsui1, M. Motoki1, K. Nakajima1, H. Ogawa1, K. Owada1, J.-S. Ricol1, I. Shimizu1, J. Shirai1, F. Suekane1, A. Suzuki1, K. Tada1, O. Tajima1, K. Tamae1, Y. Tsuda1, H. Watanabe1, J. Busenitz2, T. Classen2, Z. Djurcic2, G. Keefer2, K. McKinny2, D.-M. Mei2,‡, A. Piepke2, E. Yakushev2, B. E. Berger3, Y. D. Chan3, M. P. Decowski3, D. A. Dwyer3, S. J. Freedman3, Y. Fu3, B. K. Fujikawa3, J. Goldman3, F. Gray3, K. M. Heeger3, K. T. Lesko3, K.-B. Luk3, H. Murayama3,§, A. W. P. Poon3, H. M. Steiner3, L. A. Winslow3, G. A. Horton-Smith4,**, C. Mauger4, R. D. McKeown4, P. Vogel4, C. E. Lane5, T. Miletic5, P. W. Gorham6, G. Guillian6, J. G. Learned6, J. Maricic6, S. Matsuno6, S. Pakvasa6, S. Dazeley7, S. Hatakeyama7, A. Rojas7, R. Svoboda7, B. D. Dieterle8, J. Detwiler9, G. Gratta9, K. Ishii9, N. Tolich9, Y. Uchida9,††, M. Batygov10, W. Bugg10, Y. Efremenko10, Y. Kamyshkov10, A. Kozlov10, Y. Nakamura10, C. R. Gould11, H. J. Karwowski11, D. M. Markoff11, J. A. Messimore11, K. Nakamura11, R. M. Rohm11, W. Tornow11, R. Wendell11, A. R. Young11, M.-J. Chen12, Y.-F. Wang12, and F. Piquemal13 (KamLAND Collaboration)
1Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan
2Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA
3Physics Department, University of California at Berkeley, Berkeley, California 94720, USA, and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
4W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA
5Physics Department, Drexel University, Philadelphia, Pennsylvania 19104, USA
6Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
7Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
8Physics Department, University of New Mexico, Albuquerque, New Mexico 87131, USA
9Physics Department, Stanford University, Stanford, California 94305, USA
10Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
11Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA, and Physics Departments at Duke University, North Carolina State University, and the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
12Institute of High Energy Physics, Beijing 100039, People’s Republic of China
13CEN Bordeaux-Gradignan, IN2P3-CNRS and University Bordeaux I, F-33175 Gradignan Cedex, France
Received 15 June 2004; published 1 March 2005
We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 ν̅ e 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 ν̅ e 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 ν̅ e 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=7.9-0.5+0.6×10-5 eV2 and tan2θ=0.40-0.07+0.10, the most precise determination to date.
© 2005 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.081801
DOI:
10.1103/PhysRevLett.94.081801
PACS:
14.60.Pq, 26.65.+t, 28.50.Hw
*Present address: ICRR, University of Tokyo, Gifu, Japan †Present address: ICEPP, University of Tokyo, Tokyo, Japan ‡Present address: Los Alamos National Laboratory, Los Alamos, NM 87545, USA §Present address: School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540, USA **Present address: Kansas State University, Manhattan, KS 66506, USA ††Present address: Imperial College London, UK
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