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 candidate events with energies above 3.4 MeV compared to events expected in the absence of neutrino oscillation. Accounting for expected background events, the statistical significance for reactor 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 oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives . A global analysis of data from KamLAND and solar-neutrino experiments yields and , the most precise determination to date.
- Received 15 June 2004
DOI:https://doi.org/10.1103/PhysRevLett.94.081801
©2005 American Physical Society