A non zero, surprisingly large value of the third mixing angle $\theta_{ 13}$ has been measured in reactor neutrino experiments. Currently the most precise measurement of $\sin^2 2\theta_{ 13}$ has been performed by the Daya Bay experiment $\sin^22\theta_{ 13}=0.089\pm 0.010({ \rm stat.})\pm0.005({ \rm syst.})$ (7.7 $\sigma$ significance of $\sin^22\theta_{ 13} > 0$),the RENO experiment has measured the value $\sin^2 2\theta_{ 13} = 0.113 \pm 0.013(\rm stat.) \pm 0.019(\rm syst.)$ (4.9 $\sigma$ significance) and the Double Chooz experiment $\sin^2 2\theta_{ 13} = 0.109 \pm 0.030(\rm stat.) \pm 0.025(\rm syst.)$ (2.9 $\sigma$ significance). These results are extremely important for future searches of violation of combined CP parity in lepton sector of the Standard model.
Categories: hep-ex physics.ins-det