Trimaximal TM1 neutrino mixing in S4 with spontaneous CP violation

Understand

The measurement of the reactor angle by the Daya Bay and RENO experiments in 2012 has ruled out the tri-bimaximal paradigm.

• Adopting an S4 family symmetry, we propose direct models of the trimaximal type TM1 in which the tri-bimaximal Klein symmetry of the neutrino sector is broken to a residual Z2 symmetry.
• In such a scenario, the solar mixing angle is decreased compared to its tri-bimaximal value by about one degree, thus bringing it in excellent agreement with experimental observation.
• The atmospheric mixing angle, on the other hand, depends on the CP violating Dirac phase delta.