Leptogenesis and $CP$ violation in $SU(5)$ models with lepton flavor mixing originating from the right-handed sector

Abstract

We discuss neutrino masses and mixing in the context of seesaw type I models with three right-handed Majorana neutrinos and an approximately diagonal Dirac sector. This ansatz is motivated by the idea that the flavor structure in the right-handed Majorana masses is responsible for the large mixing angles, whereas the small mixing angle ${\theta }_{13}$ originates from the Dirac Yukawa couplings in analogy to the quark sector. To obtain ${\theta }_{13}\approx 0.15$ we study a possible $SU(5)$ grand unified theory realization with a $U(1)\times {\mathbb{Z}}_2^{\prime }\times {\mathbb{Z}}_2^{\prime \prime }\times {\mathbb{Z}}_2^{\prime \prime \prime }$ flavor symmetry and include a complex perturbation parameter in the Dirac mass matrix. The consequences for $CP$ violating phases and effects on leptogenesis are investigated.

Comments: 8 pages, 2 figures; updated with version published in PRD