Fermion Masses in SO(10) Models

TL;DR

This paper evaluates various SO(10) grand unified models for their ability to explain fermion masses and mixings, finding that models with type-I seesaw dominance fit data well, especially in minimal non-supersymmetric cases.

Contribution

It provides a comprehensive numerical analysis of fermion mass fits in different SO(10) models, highlighting the success of type-I seesaw dominance and the role of specific Higgs content and symmetries.

Findings

Type-I seesaw models fit fermion data well.

Many models fail under type-II seesaw dominance.

Minimal non-supersymmetric model with type-I seesaw gives excellent fits.

Abstract

We examine many SO(10) models for their viability or otherwise in explaining all the fermion masses and mixing angles. This study is carried out for both supersymmetric and non-supersymmetric models and with minimal ($10+\bar{126}$) and non-minimal ($10+\bar{126}+120$) Higgs content. Extensive numerical fits to fermion masses and mixing are carried out in each case assuming dominance of type-II or type-I seesaw mechanism. Required scale of the B-L breaking is identified in each case. In supersymmetric case, several sets of data at the GUT scale with or without inclusion of finite supersymmetric corrections are used. All models studied provide quite good fits if the type-I seesaw mechanism dominates while many fail if the type-II seesaw dominates. This can be traced to the absence of the $b$-$\tau$ unification at the GUT scale in these models. The minimal non-supersymmetric model with type-I seesaw dominance gives excellent fits. In the presence of a $45_H$ and an intermediate scale, the model can also account for the gauge coupling unification making it potentially interesting model for the complete unification. Structure of the Yukawa coupling matrices obtained numerically in this specific case is shown to follow from a very simple U(1) symmetry and a Froggatt-Nielsen singlet.