Leptogenesis in flavor models with type I and II seesaws

TL;DR

This paper investigates how the combination of type I and II seesaw mechanisms affects leptogenesis, especially in models with flavor symmetries, identifying conditions under which lepton asymmetry can be generated.

Contribution

It classifies flavor models with combined type I and II seesaws and analyzes their potential for successful leptogenesis, highlighting scenarios where CP asymmetry vanishes or is viable.

Findings

Certain minimal models with flavor symmetries suppress CP asymmetry.

Type II seesaw can enable leptogenesis in models where type I alone fails.

Conditions for successful leptogenesis depend on mass hierarchies and interactions.

Abstract

In type I seesaw models with flavor symmetries accounting for the lepton mixing angles the CP asymmetry in right-handed neutrino decays vanishes in the limit in which the mixing pattern is exact. We study the implications that additional degrees of freedom from type II seesaw may have for leptogenesis in such a limit. We classify in a model independent way the possible realizations of type I and II seesaw schemes, differentiating between classes in which leptogenesis is viable or not. We point out that even with the interplay of type I and II seesaws there are generic classes of minimal models in which the CP asymmetry vanishes. Finally we analyze the generation of the lepton asymmetry by solving the corresponding kinetic equations in the general case of a mild hierarchy between the light right-handed neutrino and the scalar triplet masses. We identify the possible scenarios in which leptogenesis can take place.