Reactor antineutrino experiments

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 ${\theta }_{12}$, ${\theta }_{23}$, ${\theta }_{13}$, and one CP phase. Both ${\theta }_{12}$ and ${\theta }_{23}$ are known from previous experiments. ${\theta }_{13}$ 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 ${\sin }^{2}2({\theta }_{13})$ = $0.090_{-0.009}^{+0.008}$ and the first direct measurement of the ${\bar{\nu }}_e$ mass-squared difference $\mid$$\mathrm{\Delta }{m}_{ee}^2$$\mid$ = $(2.59^{+0.19}{-0.20})\times10^{-3} \rm eV^{2}$wereobtainedrecently\mathrm{.}Thelargevalueof$\theta{13}$ boosts the next generation of reactor antineutrino experiments designed to determine the neutrino mass hierarchy, such as JUNO and RENO-50 .