Flavor Hierarchies From SU(2) Flavor and Quark-Lepton Unification

TL;DR

This paper presents a model explaining flavor hierarchies using an SU(2) flavor symmetry combined with quark-lepton unification, showing how all hierarchies can originate from a single scale ratio and predicting potential experimental signatures.

Contribution

It introduces a renormalizable model that unifies quarks and leptons to naturally generate flavor hierarchies from a single scale ratio, improving previous mechanisms.

Findings

Flavor hierarchies arise from a single scale ratio.

Model predicts signatures in upcoming charged lepton flavor violation experiments.

Thorough one-loop analysis supports the mechanism.

Abstract

In our recent attempt to explain flavor hierarchies [1], a gauged SU(2) flavor symmetry acting on left-handed fermions provides a ground to introduce three independent rank-one contributions to the Yukawa matrices: a renormalizable one for the third family, a mass-suppressed one for the second family, and an additional loop-suppressed factor for the first family. Here, we demonstrate how minimal quark-lepton unification \`a la Pati-Salam, relating down-quarks to charged leptons, can significantly improve this mechanism. We construct and thoroughly analyze a renormalizable model, performing a comprehensive one-loop matching calculation that reveals how all flavor hierarchies emerge from a single ratio of two scales. The first signatures may appear in the upcoming charged lepton flavor violation experiments.