Leptogenesis in the presence of exact flavor symmetries

TL;DR

This paper explores how leptogenesis can occur differently in models with exact flavor symmetries, emphasizing the importance of right-handed neutrino representations and flavon masses for successful asymmetry generation.

Contribution

It identifies key conditions for leptogenesis in flavor symmetric models and demonstrates these through a detailed analysis of an A4 flavor symmetry scenario.

Findings

Leptogenesis requires right-handed neutrinos in different flavor group representations.

Successful leptogenesis depends on flavons being lighter than at least one right-handed neutrino.

The study provides a concrete example with an A4 flavor symmetry model.

Abstract

In models with flavor symmetries in the leptonic sector leptogenesis can take place in a very different way compared to the standard leptogenesis scenario. We study the generation of a $B-L$ asymmetry in these kind of models in the flavor symmetric phase pointing out that successful leptogenesis requires (i) the right-handed neutrinos to lie in different representations of the flavor group; (ii) the flavons to be lighter at least that one of the right-handed neutrino representations. When these conditions are satisfied leptogenesis proceeds due to new contributions to the CP violating asymmetry and -depending on the specific model- in several stages. We demonstrate the validity of these arguments by studying in detail the generation of the $B-L$ asymmetry in a scenario of a concrete $A_4$ flavor model realization.