Variations on leptogenesis

TL;DR

This paper explores alternative leptogenesis mechanisms involving additional symmetry-breaking scales and new heavy fields, showing that viable leptogenesis can occur at lower energy scales than traditionally expected.

Contribution

It introduces a novel framework inspired by Froggatt-Nielsen models with vectorlike fields, analyzing how different hierarchies affect leptogenesis viability.

Findings

Leptogenesis can be realized at lower scales than the standard model.

Different hierarchies between $M_{N_1}$ and the new scale lead to distinct leptogenesis scenarios.

CP asymmetries are computed for all relevant cases, supporting the viability of these models.

Abstract

We study variations of the standard leptogenesis scenario that can arise if an additional mass scale related to the breaking of some new symmetry (as for example a flavor or the B-L symmetry) is present below the mass $M_{N_1}$ of the lightest right-handed Majorana neutrino. Our scheme is inspired by U(1) models of flavor \`a la Froggatt-Nielsen, and involves new vectorlike heavy fields $F$. We show that depending on the specific hierarchy between $M_{N_1}$ and the mass scale of the fields $F$, qualitatively different realizations of leptogenesis can emerge. We compute the CP asymmetries in $N_1$ decays in all the relevant cases, and we conclude that in most situations leptogenesis could be viable at scales much lower than in the standard scenario.