Towards a complete $A_4 \times SU(5)$ SUSY GUT

TL;DR

This paper presents a comprehensive supersymmetric GUT model combining $A_4$ family symmetry and $SU(5)$, accurately fitting fermion masses and mixings, and linking neutrino oscillations with leptogenesis.

Contribution

It introduces a renormalisable $A_4 imes SU(5)$ SUSY GUT model with detailed symmetry breaking and a predictive PMNS matrix without free parameters.

Findings

Achieves a fit better than one sigma to all fermion masses and mixings.

Predicts the entire PMNS matrix with no free parameters, up to a phase.

Links neutrino oscillations to leptogenesis through specific vacuum alignments.

Abstract

We propose a renormalisable model based on $A_4$ family symmetry with an $SU(5)$ grand unified theory (GUT) which leads to the minimal supersymmetric standard model (MSSM) with a two right-handed neutrino seesaw mechanism. Discrete $\mathbb{Z}_9\times \mathbb{Z}_6$ symmetry provides the fermion mass hierarchy in both the quark and lepton sectors, while $\mathbb{Z}_4^R$ symmetry is broken to $\mathbb{Z}_2^R$, identified as usual R-parity. Proton decay is highly suppressed by these symmetries. We discuss both the $A_4$ and $SU(5)$ symmetry breaking sectors, including doublet-triplet splitting, Higgs mixing and the origin of the $\mu$ term. The model provides an excellent fit (better than one sigma) to all quark and lepton (including neutrino) masses and mixing with spontaneous CP violation. With the $A_4$ vacuum alignments, $(0,1,1)$ and $(1,3,1)$, the model predicts the entire PMNS mixing matrix with no free parameters, up to a relative phase, selected to be $2\pi/3$ from a choice of the nine complex roots of unity, providing a direct link between neutrino oscillations and leptogenesis.