Results from KamLAND reactor neutrino detection

Data corresponding to a KamLAND detector exposure of 766.3 ton-years to reactor neutrinos was used to search for neutrino oscillations. Based on this data-sample, KamLAND demonstrates the reactor v(e) disappearance at the 99.998% significance and finds the reactor v(e) spectrum distortion at the 99.6% significance. The reactor neutrino anomaly defined as the flux disappearance and spectrum shape distortion is confirmed at the 99.999995% significance. A two-flavor neutrino oscillation analysis including the rate and energy spectrum yields a best fit at Delta m(2) = 7.9 x 10(-5) eV(2) and sin(2) 2 theta = 0.86. A global analysis of data from KamLAND and solar neutrino experiments yields Delta m(2) = 7.9(-0.5)(+0.6) x 10(-5) eV(2) and tan(2) theta = 0.40(-0.07)(+0.10) . The present result gives the most precise determination of Delta m(2) to date. To test the goodness of the oscillation hypothesis, the ratio of observed anti-neutrino spectrum to the expected for no-oscillation as a function of L-0/E is compared with the predictions which give neutrino-flavor changes. The neutrino oscillation is much favored with more than 99% C. L., while the decay and decoherence are excluded at the 95% and 94% C. L.