Resonant leptogenesis and TM_1 mixing in minimal type-I seesaw model with S_4 symmetry

Bikash Thapa,Ng K Francis

doi:10.1140/epjc/s10052-021-09859-2

Abstract

We present an S_4 flavour symmetric model within a minimal seesaw framework resulting in mass matrices that leads to TM_1 mixing. Minimal seesaw is realized by adding two right-handed neutrinos to the Standard Model. The model predicts Normal Hierarchy (NH) for neutrino masses. Using the constrained six-dimensional parameter space of the model, we have evaluated the effective Majorana neutrino mass, which is the parameter of interest in neutrinoless double beta decay experiments. The possibility of explaining baryogenesis via resonant leptogenesis is also examined within the model. A non-zero, resonantly enhanced CP asymmetry generated from the decay of right-handed neutrinos at the TeV scale is studied, considering flavour effects. The evolution of lepton asymmetry is discussed by solving the set of Boltzmann equations numerically and obtain the value of baryon asymmetry to be |eta _B| = 6.3 times 10^{-10} with the choice of right-handed neutrino mass, M_1 = 10 TeV and mass splitting, d simeq 10^{-8}.

Highlights

The study of the origin of neutrino flavour mixing has received much attention through the years
We have shown how the S4 model can be implemented in the minimal seesaw scenario, which results in mass matrices that lead to TM1 mixing and normal hierarchy (NH) of masses for the neutrinos
We take M1 = 10 TeV and d = (M2 − M1) /M1 10−8 in order to estimate the value of Baryon Asymmetry of the Universe (BAU)

Summary

Introduction

The study of the origin of neutrino flavour mixing has received much attention through the years. Successful realization of resonant leptogenesis is made possible by radiatively generating the mass splitting among the heavy RHN and the non-zero off-diagonal terms in the Dirac Yukawa-coupling matrix for the models presented in [33]. In their analyses low energy CP violation in neutrino oscillations is absent as a result of the exact TBM structure of the mixing matrix the only source of CP violation comes from the Majorana phases.

Model framework

Numerical analysis

Resonant leptogenesis

Conclusion