Leptogenesis in a seesaw model with Fritzsch type lepton mass matrices

TL;DR

This paper explores how the baryon asymmetry of the universe can be explained through leptogenesis in a seesaw model with Fritzsch type lepton mass matrices, analyzing the effects of CP phases and neutrino mass degeneracy.

Contribution

It demonstrates the conditions under which flavor dependent leptogenesis can produce the observed asymmetry, including the role of CP phases and mass degeneracy breaking.

Findings

Flavor dependent leptogenesis requires zero CP phases at GUT scale.

Degeneracy of heavy Majorana neutrinos must be broken for successful leptogenesis.

Radiative effects can induce the necessary mass degeneracy breaking.

Abstract

We investigate how the baryon asymmetry of our universe via leptogenesis can be achieved within the framework of the seesaw model with Fritzsch type lepton mass matrices proposed by Fukugita $et. al$. We study the cases with CP-violating phases in charged lepton Yukawa matrix, however, with and without Dirac neutrino Yukawa phases. We consider both flavor independent and flavor dependent leptogenesis, and demonstrate how they lead to different amounts of lepton asymmetries in detail. In particular, it is shown that flavor dependent leptogenesis in this model can be worked out only when the CP phases in Dirac neutrino Yukawa matrix become zero at the GUT scale. In addition to the CP phases, for successful leptogenesis in the model it is required that the degeneracy of the heavy Majorana neutrino mass spectrum should be broken and we also show that the breakdown of the degeneracy can be radiatively induced.