Observation of Electron-Antineutrino Disappearance at Daya Bay

The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle θ₁₃ with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW_th reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43000ton-GW_th-day live-time exposure in 55 days, 10 416 (80 376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R=0.940±0.011(stat.)±0.004(syst.). A rate-only analysis finds sin⁡²2θ₁₃=0.092±0.016(stat.)±0.005(syst.) in a three-neutrino framework.