Electron-antineutrino Disappearance Observed by the Daya Bay Reactor Neutrino Experiment

The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle θ13 with a significance of 7.7 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected by six 20-ton target-mass detectors of identical design, deployed in two near and one far underground experimental halls. With a 116.8 kton-GWth-day live-time exposure in 139 days, 28,909 and 205,308 electron-antineutrino candidates were detected at the far hall and near halls respectively. The ratio of the observed to expected number of antineutrinos at the far hall is R=0.944±0.007(stat)±0.003(syst). A rate-only analysis finds sin22θ13=0.089±0.010(stat)±0.005(syst) in a three-neutrino framework. The experiments will continue for several years and a more precise neutrino mixing angle θ13 will be given in the future.