Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (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 ex...

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Veröffentlicht in:	Physical review letters 2005-03, Vol.94 (8), p.081801-081801, Article 081801
Hauptverfasser:	Araki, T, Eguchi, K, Enomoto, S, Furuno, K, Ichimura, K, Ikeda, H, Inoue, K, Ishihara, K, Iwamoto, T, Kawashima, T, Kishimoto, Y, Koga, M, Koseki, Y, Maeda, T, Mitsui, T, Motoki, M, Nakajima, K, Ogawa, H, Owada, K, Ricol, J-S, Shimizu, I, Shirai, J, Suekane, F, Suzuki, A, Tada, K, Tajima, O, Tamae, K, Tsuda, Y, Watanabe, H, Busenitz, J, Classen, T, Djurcic, Z, Keefer, G, McKinny, K, Mei, D-M, Piepke, A, Yakushev, E, Berger, B E, Chan, Y D, Decowski, M P, Dwyer, D A, Freedman, S J, Fu, Y, Fujikawa, B K, Goldman, J, Gray, F, Heeger, K M, Lesko, K T, Luk, K-B, Murayama, H, Poon, A W P, Steiner, H M, Winslow, L A, Horton-Smith, G A, Mauger, C, McKeown, R D, Vogel, P, Lane, C E, Miletic, T, Gorham, P W, Guillian, G, Learned, J G, Maricic, J, Matsuno, S, Pakvasa, S, Dazeley, S, Hatakeyama, S, Rojas, A, Svoboda, R, Dieterle, B D, Detwiler, J, Gratta, G, Ishii, K, Tolich, N, Uchida, Y, Batygov, M, Bugg, W, Efremenko, Y, Kamyshkov, Y, Kozlov, A, Nakamura, Y, Gould, C R, Karwowski, H J, Markoff, D M, Messimore, J A, Nakamura, K, Rohm, R M, Tornow, W, Wendell, R, Young, A R, Chen, M-J, Wang, Y-F, Piquemal, F
Format:	Artikel
Sprache:	eng
Schlagworte:	High Energy Physics - Experiment Physics
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Zusammenfassung:	We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (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 nu (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 nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.
ISSN:	0031-9007 1079-7114
DOI:	10.1103/physrevlett.94.081801