Magic neutrino mass model with broken $\mu-\tau$ symmetry and Leptogenesis

TL;DR

This paper presents a flavor model with broken $$ symmetry that explains neutrino masses and mixing, predicts observable neutrinoless double beta decay, and successfully accounts for baryogenesis via leptogenesis, especially favoring normal hierarchy.

Contribution

It introduces a minimal $A_4$ flavor model with broken $$ symmetry and two right-handed neutrinos, incorporating type-I and II seesaw mechanisms to explain neutrino properties and baryon asymmetry.

Findings

Effective Majorana mass $|M_{ee}|$ within $0 uetaeta$ sensitivity for inverted hierarchy.

Baryon asymmetry matches observations for normal hierarchy.

Inverted hierarchy is disfavored due to non-observation of $0 uetaeta$ at nEXO.

Abstract

We investigate baryogenesis via leptogenesis in $A_4$ flavor model within the paradigm of type-I and II seesaw mechanism resulting in magic neutrino mass matrix with broken $\mu-\tau$ symmetry in a minimal scenario with two right-handed neutrinos(2RHN). Additional $Z_3$ cyclic symmetry is employed to constrain the Yukawa structure of model. The type-II seesaw terms play crucial role in generating non-degenerate neutrino masses and non-zero $\theta_{13}$ and contribute in baryogenesis. In particular, after the spontaneous symmetry breaking, the Yukawa couplings $y_{\Delta_1}$ and $y_{\Delta_3}$ are responsible for the breaking of $\mu-\tau$ symmetry. The effective Majorana neutrino mass $|M_{ee}|$ is found to be well within the sensitivity reach of the $0\nu\beta\beta$ experiments, in particular, for inverted hierarchy. The model has imperative implication for inverted hierarchy, for example, the non-observation of this process at nEXO will rule out IH. The predicted baryon asymmetry is in good agreement with the observed baryon asymmetry for NH whereas IH is disallowed at 2.5$\sigma$ C.L..