Measurement of Reactor Antineutrino Oscillation Amplitude and Frequency at RENO

TL;DR

The RENO experiment precisely measured reactor antineutrino oscillation parameters, including amplitude and frequency, confirming energy-dependent disappearance consistent with neutrino oscillation theory.

Contribution

This study provides the most precise measurements to date of $ heta_{13}$ and $| riangle m_{ee}^2|$ using extensive data from near and far detectors over several years.

Findings

Measured $ heta_{13}$ as 0.0896 with uncertainties

Determined $| riangle m_{ee}^2|$ as 2.68 x 10^{-3} eV^2

Observed clear energy-dependent antineutrino disappearance

Abstract

The RENO experiment reports more precisely measured values of $\theta_{13}$ and $|\Delta m_{ee}^2|$ using $\sim$2\,200 live days of data. The amplitude and frequency of reactor electron antineutrino ($\overline{\nu}_e$) oscillation are measured by comparing the prompt signal spectra obtained from two identical near and far detectors. In the period between August 2011 and February 2018, the far (near) detector observed 103\,212 (850\,666) electron antineutrino candidate events with a background fraction of 4.7\% (2.0\%). A clear energy and baseline dependent disappearance of reactor $\overline{\nu}_e$ is observed in the deficit of the measured number of $\overline{\nu}_e$. Based on the measured far-to-near ratio of prompt spectra, we obtain $\sin^2 2 \theta_{13} = 0.0896 \pm 0.0048({\rm stat}) \pm 0.0048({\rm syst})$ and $|\Delta m_{ee}^2| =[2.68 \pm 0.12({\rm stat}) \pm 0.07({\rm syst})]\times 10^{-3}$~eV$^2$.