| Between Apr. 2002 and May 2006 KamLAND measured the electron antineutrino flux at the Kamioka mine (2700 m.w.e.) in Japan. The nue sources were 19 Japanese nuclear reactor facilities at distances of 87 km to 830 km. Antineutrinos were detected by inverse beta decay, nue + p → e+ + n; detection of a positron and neutron pair constituted a neutrino signal. 1 kton of liquid scintillator served as both target and detector; the total exposure was 4.14 x 1034 proton days. In 1179.3 days of detector livetime, 550 antineutrino interactions were detected above a 3.4 MeV threshold, with an estimated 55 +/- 18 from backgrounds. The number, spectrum, and time of the nu e signals support neutrino flavor oscillation with Dm212 = (7.72 +/- 0.24) x 105 eV 2 and tan2theta12 = 0.48 +/- 0.12, in the Large Mixing Angle region. Assuming CPT invariance, KamLAND and solar neutrino results combined give Dm212 = (7.71 +/- 0.25) x 105 eV 2 and tan2theta12 = 0.49 +/- 0.05. |
