Constrained Flavor Breaking

TL;DR

This paper investigates flavor models based on subgroups of the standard model's flavor symmetry, deriving relations among Yukawa matrices that connect quark and lepton masses and mixing, with implications for flavor-changing processes.

Contribution

It introduces a global $SU(3)^3$ flavor symmetry model with minimal breaking, establishing a novel relation among Yukawa matrices and explaining large leptonic mixing angles.

Findings

Charged-lepton mass ratios are linked to quark masses and mixing angles.

Large leptonic mixing angles are natural in this framework.

Model predicts flavor-changing neutral currents in charged leptons.

Abstract

We explore predictive flavor models based on subgroups of the standard-model $SU(3)^5$ flavor symmetry. Restricting to products of $SU(3)$, we find that a global $SU(3)^3$ flavor symmetry, broken only by two Yukawa spurions, leads to a relation among down-type quark, up-type quark and charged-lepton Yukawa matrices: $Y_d \propto Y_u Y_e^\dagger$. As a result, the charged-lepton mass ratios are expressed in terms of quark mass ratios and mixing angles. Large leptonic mixing angles appear to be natural and lead to contributions to flavor-changing neutral currents in the charged-lepton sector, which can be tested in future precision experiments.