Flavon assisted low scale leptogenesis

TL;DR

This paper proposes that flavon fields in flavor-symmetry models can serve as the scalar singlet in low-scale leptogenesis, enabling successful baryogenesis without requiring degenerate RHN masses.

Contribution

It identifies flavon fields as natural candidates for the scalar singlet in low-scale leptogenesis models, connecting flavor symmetry with baryogenesis mechanisms.

Findings

Flavon fields can facilitate low-scale leptogenesis without mass degeneracy.

The model reproduces observed neutrino masses and mixing angles.

Baryon asymmetry is achievable within experimental constraints.

Abstract

Low-scale leptogenesis scenarios, such as the resonant or ARS leptogenesis, typically require a highly degenerate mass spectrum of right-handed neutrinos (RHNs). This requirement can be circumvented by extending the seesaw framework with a scalar singlet $S$ that couples to RHNs via the $S N^{}_I N^{}_J$ terms (with $I \neq J$), which opens up new decay channels $N^{}_I \to N^{}_J S$ and provides additional sources of CP violation, thereby enabling successful leptogenesis at the TeV scale without the need for mass degeneracy. In this work, we point out that the flavon fields, which are introduced in many flavor-symmetry neutrino mass models to be responsible for the generation of RHN masses through the acquisition of non-zero vacuum expectation values, serve as ideal candidates for the $S$ field. Taking as an example a flavor-symmetry neutrino mass model that naturally realizes the experimentally allowed TM1 mixing pattern and has the attractive features that only one flavon field plays the role of $S$ and that it couples to only two RHNs, we demonstrate that the observed neutrino masses and mixing angles can be consistently reproduced, while the observed baryon asymmetry can be achieved within a parameter space compatible with current experimental constraints.