Spectral Measurement of the Electron Antineutrino Oscillation Amplitude and Frequency using 500 Live Days of RENO Data

Abstract

The Reactor Experiment for Neutrino Oscillation (RENO) has been taking electron antineutrino (${\overline{\nu }}_e$) data from the reactors in Yonggwang, Korea, using two identical detectors since August 2011. Using roughly 500 live days of data through January 2013 we observe 290,775 (31,514) reactor ${\overline{\nu }}_e$ candidate events with 2.8 (4.9)% background in the near (far) detector. The observed visible positron spectra from the reactor ${\overline{\nu }}_e$ events in both detectors show discrepancy around 5 MeV with regard to the prediction from the current reactor ${\overline{\nu }}_e$ model. Based on a far-to-near ratio measurement using the spectral and rate information we have obtained ${\sin }^{2}2{\theta }_{13}=0.082\pm 0.009(stat.)\pm 0.006(syst.)$ and $|\Delta m_{ee}^2|=[2.62_{-0.23}^{+0.21}(stat.{)}_{-0.13}^{+0.12}(syst.)]\times 10^{-3}$eV${}^2$.

24 pages, 30 figures. Submitted to PRD. Total detection efficiency change from 76.44% to 76.47%. Some modifications of text to improve readability and clarification of the paper