The minimal adjoint-SU(5)xZ_4 GUT model

TL;DR

This paper proposes an extended SU(5) grand unified theory with Z_4 flavor symmetry, leading to specific fermion mass structures, neutrino mass generation mechanisms, and proton stability, with implications for neutrino hierarchy.

Contribution

It introduces a novel SU(5) x Z_4 model that constrains fermion mass matrices, incorporates multiple neutrino mass mechanisms, and predicts specific neutrino hierarchies and proton stability.

Findings

Neutrino mass matrices have only two viable zero textures.

One texture supports normal hierarchy, the other inverted.

Z_4 symmetry prevents proton decay via color triplet exchange.

Abstract

An extension of the adjoint SU(5) model with a flavour symmetry based on the Z_4 group is investigated. The Z_4 symmetry is introduced with the aim of leading the up- and down-quark mass matrices to the Nearest-Neighbour-Interaction form. As a consequence of the discrete symmetry embedded in the SU(5) gauge group, the charged lepton mass matrix also gets the same form. Within this model, light neutrinos get their masses through type-I, type-III and one-loop radiative seesaw mechanisms, implemented, respectively, via a singlet, a triplet and an octet from the adjoint fermionic 24 fields. It is demonstrated that the neutrino phenomenology forces the introduction of at least three 24 fermionic multiplets. The symmetry SU(5)xZ_4 allows only two viable zero textures for the effective neutrino mass matrix. It is showed that one texture is only compatible with normal hierarchy and the other with inverted hierarchy in the light neutrino mass spectrum. Finally, it is also demonstrated that Z_4 freezes out the possibility of proton decay through exchange of colour Higgs triplets at tree-level.