Majorana Phases and Leptogenesis in See-Saw Models with A_4 Symmetry

TL;DR

This paper explores how Majorana CP violation and leptogenesis are interconnected in supersymmetric A_4 symmetric see-saw models, linking low-energy phases to the Universe's baryon asymmetry.

Contribution

It demonstrates that A_4 models with minimal parameters can produce correct baryon asymmetry and relates its sign to Majorana phases.

Findings

Correct size and sign of baryon asymmetry can be generated.

Majorana phases constrain leptogenesis CP violation.

Sign of baryon asymmetry linked to Majorana phase sines.

Abstract

The related issues of Majorana CP violation in the lepton sector and leptogenesis are investigated in detail in two rather generic supersymmetric models with type I see-saw mechanism of neutrino mass generation and A_4 flavour symmetry, which naturally lead at leading order to tri-bimaximal neutrino mixing. The neutrino sector in this class of models is described at leading order by just two real parameters and one phase. This leads, in particular, to significant low energy constraints on the Majorana phases \alpha_{21} and \alpha_{31} in the PMNS matrix, which play the role of leptogenesis CP violating parameters in the generation of the baryon asymmetry of the Universe. We find that it is possible to generate the correct size and sign of the baryon asymmetry in both A_4 models. The sign of the baryon asymmetry is directly related to the signs of sin\alpha_{21} and/or sin\alpha_{31}.