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Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion

Abstract : 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.
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Submitted on : Friday, February 10, 2006 - 10:52:02 AM
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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, American Physical Society, 2005, 94, pp.081801. ⟨10.1103/PhysRevLett.94.081801⟩. ⟨in2p3-00025603⟩



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