Paper detail

Observation of Energy and Baseline Dependent Reactor Antineutrino Disappearance in the RENO Experiment

The RENO experiment has analyzed about 500 live days of data to observe an energy dependent disappearance of reactor $\overlineν_e$ by comparison of their prompt signal spectra measured in two identical near and far detectors. In the period between August 2011 and January 2013, the far (near) detector observed 31541 (290775) electron antineutrino candidate events with a background fraction of 4.9\% (2.8\%). The measured prompt spectra show an excess of reactor $\overlineν_e$ around 5 MeV relative to the prediction from a most commonly used model. A clear energy and baseline dependent disappearance of reactor $\overlineν_e$ is observed in the deficit of the observed number of $\overlineν_e$. Based on the measured far-to-near ratio of prompt spectra, we obtain $\sin^2 2 θ_{13} = 0.082 \pm 0.009({\rm stat.}) \pm 0.006({\rm syst.})$ and $|Δm_{ee}^2| =[2.62_{-0.23}^{+0.21}({\rm stat.}) _{-0.13}^{+0.12}({\rm syst.})]\times 10^{-3}$~eV$^2$.