Resonant leptogenesis and tribimaximal leptonic mixing with A4 symmetry

TL;DR

This paper explores how thermal leptogenesis can occur in models with A4 symmetry that produce tribimaximal neutrino mixing, focusing on the effects of symmetry breaking on neutrino mass degeneracy and leptogenesis viability.

Contribution

It demonstrates that leptogenesis is feasible in A4 symmetric models by lifting neutrino mass degeneracy through renormalization group effects or soft symmetry breaking.

Findings

Leptogenesis viability depends on degeneracy lifting mechanisms.

Exact tribimaximal mixing is achieved at high scale.

Implications for low-energy neutrino observables are discussed.

Abstract

We investigate the viability of thermal leptogenesis in type-I seesaw models with leptonic flavour symmetries that lead to tribimaximal neutrino mixing. We consider an effective theory with an A4 x Z3 x Z4 symmetry, which is spontaneously broken at a scale much higher than the electroweak scale. At the high scale, leptonic Yukawa interactions lead to exact tribimaximal mixing and the heavy Majorana neutrino mass spectrum is exactly degenerate. In this framework, leptogenesis becomes viable once this degeneracy is lifted either by renormalization group effects or by a soft breaking of the A4 symmetry. The implications for low-energy neutrino physics are discussed.