Fermion masses and mixing in models with SO(10) x A_4 symmetry

TL;DR

This paper explores fermion masses and mixing patterns in models with $SO(10) imes A_4$ symmetry, identifying key ingredients for tri-bi-maximal mixing and proposing a universal seesaw mechanism for mass hierarchies.

Contribution

It systematically identifies the ingredients needed for tri-bi-maximal mixing in $SO(10) imes A_4$ models and introduces a universal seesaw mechanism for fermion mass hierarchies.

Findings

Identification of ingredients for tri-bi-maximal mixing.

Proposal of a universal seesaw mechanism for mass hierarchies.

Analysis of non-renormalizable operators' role in fermion masses.

Abstract

We study the flavour sector in models where the three families of matter are unified in a $(16,3)$ representation of the $SO(10)\times A_4$ group. The necessary ingredients to realize tri-bi-maximal mixing in the lepton sector are identified systematically. The non-renormalizable operators contributing to the fermion mass matrices play an important role. We also present a mechanism to explain the inter-family mass hierarchy of quarks and charged leptons, which relies on a `universal seesaw' mechanism and is compatible with tri-bi-maximal mixing.