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

TL;DR

This paper reports on the spectral measurement of electron antineutrino oscillation parameters using 500 days of data from the RENO experiment, revealing oscillation amplitude and frequency consistent with neutrino oscillation theory.

Contribution

First spectral measurement of electron antineutrino oscillation amplitude and frequency using RENO data, providing precise values for mixing angle and mass-squared difference.

Findings

Measured $ heta_{13}$ with high precision.

Determined $| riangle m_{ee}^2|$ consistent with previous results.

Observed spectral discrepancies around 5 MeV in reactor models.

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 $\sin^2 2 \theta_{13} = 0.082 \pm 0.009({\rm stat.}) \pm 0.006({\rm syst.})$ and $|\Delta m_{ee}^2| =[2.62_{-0.23}^{+0.21}({\rm stat.})_{-0.13}^{+0.12}({\rm syst.})]\times 10^{-3}$eV$^2$.