Chasing $\theta_{13}$ with new reactor neutrino experiments

Abstract

It is now widely accepted that a new middle baseline disappearance reactor neutrino experiment with multiple detectors could provide a clean measurement of the $\theta_{13}$ mixing angle, free from any parameter degeneracies and correlations induced by matter effect and the unknown leptonic Dirac CP phase. The current best constraint on the third mixing angle comes from the Chooz reactor neutrino experiment $\sin^{2}(2\theta_{13})<0.2$ (90$ %$ C.L., $\Delta m_{\rm atm}^{2}=2.0 10^{-3}$ eV$^{2}$). Several projects of experiment, with different timescales, have been proposed over the last two years all around the world. Their sensitivities range from $\sin^{2}(2\theta_{13})<$ 0.01 to 0.03, having thus an excellent discovery potential of the $\nu_e$ fraction of $\nu_3$.