Admixture of quasi-Dirac and Majorana neutrinos with tri-bimaximal mixing

Understand

We propose a realization of the so-called bimodal/schizophrenic model proposed recently.

• We assume S4, the permutation group of four objects as flavor symmetry giving tri-bimaximal lepton mixing at leading order.
• In these models the second massive neutrino state is assumed quasi-Dirac and the remaining neutrinos are Majorana states.
• In the case of inverse mass hierarchy, the lower bound on the neutrinoless double beta decay parameter m_ee is about two times that of the usual lower bound, within the range of sensitivity of the next generation of experiments.