Quark sector of S3 models: classification and comparison with experimental data

TL;DR

This paper classifies various S3 flavor symmetry models for quarks, analyzes their mass matrices, derives CKM matrix expressions, and compares them with experimental data, showing S3 as a promising symmetry in the quark sector.

Contribution

It provides a comprehensive classification and comparison of S3 models with different Higgs content, deriving analytical CKM expressions and validating them against experimental data.

Findings

S3 models can reproduce texture zero and NNI mass matrices.

Derived CKM matrix expressions match experimental data well.

Adding Higgs doublets in S3 representations enhances model viability.

Abstract

S3 models offer a low energy approach to describe the observed pattern of masses and mixing, of both quarks and leptons. In this work, we first revisit an S3 model with only one Higgs electroweak doublet, where the flavour symmetry must be broken in order to produce an acceptable pattern of masses and mixing for fermions. Then, we analyse different S3 models, where the flavour symmetry is preserved as an exact, but hidden symmetry of the low energy spectra, after the electroweak symmetry breaking. The latter models require the addition of two more Higgs electroweak doublets which are accommodated in an S3 doublet. We also explore the consequences of adding a fourth Higgs electroweak doublet, thus occupying all three irreducible representations of S3. We show how the various S3-invariant mass matrices of the different models can reproduce the two texture zeroes and Nearest Neighbour Interaction matrix forms, which have been found to provide a viable and universal treatment of mixing for both quarks and leptons. We also find analytical and exact expressions for the CKM matrix of the models in terms of quark mass ratios. Finally, we compare the expressions of the CKM matrix of the different S3 models with the most up to date values of masses and mixing in the quark sector, via a chi^2 analysis. We find that the analytical expressions we derived reproduce remarkably well the most recent experimental data of the CKM matrix, suggesting that S3 is a symmetry of the quark sector.