Measurement of reactor antineutrino oscillation amplitude and frequency using 3800 days of complete data sample of the RENO experiment

Abstract

We report an updated neutrino mixing angle of $\hat{I}{¸}_{13}$ obtained from a complete data sample of the RENO experiment. The experiment has measured the amplitude and frequency of reactor anti-electron-neutrinos ($\bar{\hat{I}}{½}_e$) oscillations at the Hanbit nuclear power plant, Younggwang, Korea, since August 2011. As of March 2023, the data acquisition was completed after a total of 3800 live days of detector operation. The observed candidates via inverse beta decay (IBD) are 1,211,995 (144,667) in the near (far) detector. Based on an observed energy-dependent reactor neutrino disappearance, neutrino oscillation parameters of $\hat{I}{¸}_{13}$ and $|\hat{I}”m_{ee}^2|$ are precisely determined as ${\sin }^{2}2\hat{I}{¸}_{13}=0.0920_{-0.0042}^{+0.0044}(\text{stat.}{)}_{-0.0041}^{+0.0041}(\text{syst.})$ and $|\hat{I}”m_{ee}^2|=\left[2.57_{-0.11}^{+0.10}(\text{stat.}{)}_{-0.05}^{+0.05}(\text{syst.})\right]\times 10^{-3}{\text{eV}}^2$. Compared to the previous RENO results published in Ref.~\cite{PhysRevLett.121.201801}, the precision is improved from 7.5\% to 6.4\% for ${\sin }^{2}2\hat{I}{¸}_{13}$ and from 5.2\% to 4.5\% for $|\hat{I}”m_{ee}^2|$. The statistical error of the measurement has reached our goal and is hardly improved with additional data-taking.

13 pages, 11 figures