Antineutrino science in KamLAND

The primary goal of KamLAND is a search for the oscillation of anti νe's emitted from distant power reactors. The long baseline, typically 180 km, enables KamLAND to address the oscillation solution of the ''solar neutrino problem'' with anti νe's under laboratory conditions. KamLAND found fewer reactor anti νe events than expected from standard assumptions about anti νe propagation at more than 9 σ confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at more than 5 σ C.L., and prefers the distortion from neutrino oscillation effects. A three-flavor oscillation analysis of the data from KamLAND and KamLAND + solar neutrino experiments with CPT invariance, yields Δm212 = [7.54-0.18+0.19 x 10-5 eV2, 7.53-0.18+0.19 x 10-5 eV2], tan2θ12 = [0.481-0.080+0.092, 0.437-0.026+0.029], and sin2θ13 = [0.010-0.034+0.033, 0.023-0.015+0.015]. All solutions to the solar neutrino problem except for the large mixing angle region are excluded. KamLAND also demonstrated almost two cycles of the periodic feature expected from neutrino oscillation effects. KamLAND performed the first experimental study of antineutrinos from the Earth's interior so-called geoneutrinos (geo anti νe's), and succeeded in detecting geo anti νe's produced by the decays of 238U and 232Th within the Earth. Assuming a chondritic Th/U mass ratio, we obtain 116-27+28 anti νe events from 238U and 232Th, corresponding a geo anti νe flux of 3.4-0.8+0.8 x 106 cm-2s-1 at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geo anti νe rate. (orig.)