Low scale leptogenesis in a hybrid model of the scotogenic type I and III seesaw models

Daijiro Suematsu

doi:10.1103/physrevd.100.055008

Abstract

The scotogenic type I and type III seesaw models are good candidates to explain the existence of neutrino masses and dark matter simultaneously. However, since triplet fermions have SU(2) gauge interaction, they cannot be out of equilibrium before the electroweak symmetry breaking. Thus, leptogenesis seems to be difficult within a framework of the pure type III seesaw model. Some extension seems to be required to solve this fault. A model extended by introducing a singlet fermion could be such a simple example. If the singlet fermion is in the thermal equilibrium even for its extremely small neutrino Yukawa coupling, leptogenesis could be shown to occur successfully for a rather low mass of the singlet fermion. The required mass could be lowered to $10^4$~GeV.

Highlights

Leptogenesis is considered to be the most promising scenario for the generation of baryon number asymmetry in the Universe [1,2]
We proposed a simple extension of the model by introducing a singlet fermion so as to incorporate successful leptogenesis
If its thermal equilibrium could be prepared not through its Yukawa couplings but through other interactions, the leptogenesis caused by its decay at a low temperature region could explain the required baryon number asymmetry

Summary

INTRODUCTION

Leptogenesis is considered to be the most promising scenario for the generation of baryon number asymmetry in the Universe [1,2]. Only a restricted range of the neutrino Yukawa couplings is expected to cause the required baryon number asymmetry via the leptogenesis successfully. This feature requires the mass of the right-handed neutrinos in the. We find a similar feature in the scotogenic type I seesaw model [7], which is a well-known model for both neutrino masses and dark matter (DM) [8,9] In this model, the righthanded neutrinos whose masses are in TeV ranges could have a chance to be a candidate for both DM and a mother field of leptogenesis [10]. The scotogenic type III seesaw model is known as another model which can connect the neutrino mass generation and the existence of DM at low energy regions [11].

Neutrino mass and DM abundance in scotogenic type III seesaw

A simple extension of the model

LEPTOGENESIS

SUMMARY