Reactor antineutrino experiments

Abstract

Neutrinos are elementary particles in the standard model of particle physics. There are 3 flavors of neutrinos that oscillate among themselves. Their oscillation can be described by a 3$\times$3 unitary matrix, containing three mixing angles $\hat{I}{¸}_{12}$, $\hat{I}{¸}_{23}$, $\hat{I}{¸}_{13}$, and one CP phase. Both $\hat{I}{¸}_{12}$ and $\hat{I}{¸}_{23}$ are known from previous experiments. $\hat{I}{¸}_{13}$ was unknown just two years ago. The Daya Bay experiment gave the first definitive non-zero value in 2012. An improved measurement of the oscillation amplitude ${\sin }^{2}2(\hat{I}{¸}_{13})$ = $0.090_{-0.009}^{+0.008}$ and the first direct measurement of the $\bar{\hat{I}}{½}_e$ mass-squared difference $\mid$$\hat{I}”m_{ee}^2$$\mid$ = $(2.59_{-0.20}^{+0.19})\times 10^{-3}\mathrm{e}{\mathrm{V}}^2$ were obtained recently. The large value of $\hat{I}{¸}_{13}$ boosts the next generation of reactor antineutrino experiments designed to determine the neutrino mass hierarchy, such as JUNO and RENO-50 .