A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (${\overline{\nu }}_e$) from six $2.9{\mathrm{GW}}_{\mathrm{th}}$ reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude ${\sin }^{2}2{\theta }_{13}=0.090_{-0.009}^{+0.008}$ and the first direct measurement of the ${\overline{\nu }}_e$ mass-squared difference $|\mathrm{\Delta }{m}_{ee}^2|=(2.59_{-0.20}^{+0.19})\times {10}^{-3}{\mathrm{e}\mathrm{V}}^2$ is obtained using the observed ${\overline{\nu }}_e$ rates and energy spectra in a three-neutrino framework. This value of $|\mathrm{\Delta }{m}_{ee}^2|$ is consistent with $|\mathrm{\Delta }{m}_{\mu \mu }^2|$ measured by muon neutrino disappearance, supporting the three-flavor oscillation model.

The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle θ 13 with a sensitivity better than 0.01 in the parameter sin 22θ 13 at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties are smaller than requirements. © 2012 Elsevier B.V. All rights reserved.postprin

A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment’s unique configuration of multiple baselines from six 2.9 ${\mathrm{GW}}_{\mathrm{th}}$ nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the ${10}^{-3}{\mathrm{eV}}^2<|\mathrm{\Delta }{m}_{41}^2|<0.3{\mathrm{eV}}^2$ range. The relative spectral distortion due to the disappearance of electron antineutrinos was found to be consistent with that of the three-flavor oscillation model. The derived limits on ${\sin }^{2}2{\theta }_{14}$ cover the ${10}^{-3}{\mathrm{eV}}^2\lesssim |\mathrm{\Delta }{m}_{41}^2|\lesssim 0.1{\mathrm{eV}}^2$ region, which was largely unexplored.