Spectral measurement of the electron antineutrino oscillation amplitude and frequency using 500 live days of RENO data

The Reactor Experiment for Neutrino Oscillation (RENO) has been taking electron antineutrino (${\overline{\ensuremath{\nu}}}_{e}$) 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 ${\overline{\ensuremath{\nu}}}_{e}$ candidate events with 2.8% (4.9%) background in the near (far) detector. The observed visible positron spectra from the reactor ${\overline{\ensuremath{\nu}}}_{e}$ events in both detectors show a discrepancy around 5 MeV with regard to the prediction from the current reactor ${\overline{\ensuremath{\nu}}}_{e}$ model. Based on a far-to-near ratio measurement using the spectral and rate information, we have obtained ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{13}=0.082\ifmmode\pm\else\textpm\fi{}0.009(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.006(\mathrm{syst}.)$ and $|\mathrm{\ensuremath{\Delta}}{m}_{ee}^{2}|=[2.6{2}_{\ensuremath{-}0.23}^{+0.21}(\mathrm{stat}.{)}_{\ensuremath{-}0.13}^{+0.12}(\mathrm{syst}.)]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{eV}}^{2}$.