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 = 18.104.22.168 × 10-5 eV2 and tan2θ = 0.400.07+0.10 the most precise determination to date.
ASJC Scopus subject areas
- Physics and Astronomy(all)