Light sterile neutrino and leptogenesis

TL;DR

This paper explores how models with three heavy Majorana neutrinos and a minimal-extended seesaw mechanism involving a light sterile neutrino can explain leptogenesis and neutrino mass ordering, linking high-energy processes to low-energy experiments.

Contribution

It demonstrates that the mass ordering and Majorana scales can be determined using the Casas-Ibarra parametrization with an orthogonal matrix, incorporating a light sterile neutrino into leptogenesis models.

Findings

The existence of a light sterile neutrino is necessary for high-energy lepton asymmetry.

The model links CP asymmetry and dilution mass to neutrino mass and mixing parameters.

Constraints from low-energy experiments help narrow down model parameters.

Abstract

We studied models of leptogenesis where three right-handed Majorana neutrinos are involved and the minimal-extended seesaw mechanism including an additional singlet field produces four light neutrinos. This study shows that the type of mass ordering and heavy Majorana scales can be determined by inputting the simplest orthogonal matrix into the Casas-Ibarra(CI) representation of seesaw. The CP asymmetry produced from the decays of heavy neutrinos and the dilution mass are predicted in terms of the mass and mixing elements of the fourth neutrino. Upon the choice of CI matrix, the existence of a light sterile neutrino is required to explain the high-energy lepton asymmetry in light of phenomenological measurements. Although there are several free parameters attributable to an additional neutrino, the model can be in part constrained by low-energy experiments such as sterile neutrino searches and neutrinoless double-beta decays, as well as the observed baryon asymmetry in the universe.