Leptogenesis in the littlest inverse seesaw model

TL;DR

This paper explores how the littlest inverse seesaw model can successfully generate the observed matter-antimatter asymmetry through leptogenesis, using two different mechanisms without extra parameters.

Contribution

It demonstrates that the LIS model can realize leptogenesis via resonant and ARS mechanisms, providing a minimal and predictive low-scale leptogenesis framework.

Findings

Leptogenesis can be achieved in the LIS model with small parameter adjustments.

Resonant leptogenesis occurs via RGE-induced mass splittings in degenerate sterile neutrinos.

ARS leptogenesis is viable with hierarchical sterile neutrino masses.

Abstract

The littlest inverse seesaw (LIS) model represents the first low-scale seesaw framework to successfully account for all six physical observables of the neutrino sector with merely two effective free parameters, making it highly worthy of in-depth investigation. In this work, we investigate realizations of leptogenesis in this framework. We consider two distinct scenarios. In the first, the two pseudo-Dirac sterile neutrino pairs are initially exactly degenerate and subsequently acquire small mass splittings via the RGE effects, enabling resonant leptogenesis to occur across different PD pairs and consequently enhancing leptogenesis. In the second, the two PD pairs feature a hierarchical mass spectrum, and leptogenesis proceeds via sterile neutrino oscillations through the ARS mechanism. We show that the observed baryon asymmetry can be successfully reproduced in sizable regions of the parameter space without introducing additional free parameters, demonstrating that the LIS framework provides a viable and predictive setting for low-scale leptogenesis.