Constraining Low-Scale Flavor Models with $\boldsymbol{(g-2)_{\mu}}$ and Lepton Flavor Violation

TL;DR

This paper examines how low-scale flavor symmetry models can explain the muon g-2 anomaly while satisfying lepton flavor violation constraints, highlighting the challenges and limitations of existing models.

Contribution

It provides concrete examples of low-scale flavor models that address the muon g-2 discrepancy and analyzes the constraints imposed by lepton flavor violation.

Findings

Low-scale flavor models can account for (g-2)_μ with specific flavor structures.

LFV constraints strongly limit off-diagonal Yukawa couplings in these models.

Many popular flavor models are incompatible with the combined requirements.

Abstract

We present here two concrete examples of models where a sub-TeV scale breaking of their respective $\mathcal{T}_{13}$ and $A_5$ flavor symmetries is able to account for the recently observed discrepancy in the muon anomalous magnetic moment, $(g-2)_\mu$. Similarities in the flavor structures of the charged-lepton Yukawa matrix and dipole matrix yielding $(g-2)_\mu$ give rise to strong constraints on low-scale flavor models when bounds from lepton flavor violation (LFV) are imposed. These constraints place stringent limits on the off-diagonal Yukawa structure, suggesting a mostly (quasi-)diagonal texture for models with a low flavor breaking scale $\Lambda_f$. We argue that many of the popular flavor models in the literature designed to explain the fermion masses and mixings are not suitable for reproducing the observed discrepancy in $(g-2)_\mu$, which requires a delicate balance of maintaining a low flavor scale while simultaneously satisfying strong LFV constraints.