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. Ricol (1) , I. 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 (1)

1 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 [overline 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 [overline 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 [overline nu ]e oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam2=7.9_-0.5^+0.6×10-5 eV2. A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam2=7.9_-0.5^+0.6×10-5 eV2 and tan2theta=0.40_-0.07^+0.10, the most precise determination to date.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

T. Araki, K. Eguchi, S. Enomoto, K. Furuno, K. Ichimura, et al.. Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion. Physical Review Letters, 2005, 94, pp.081801. ⟨10.1103/PhysRevLett.94.081801⟩. ⟨in2p3-00025603⟩