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

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.

Comments: 22+12 pages, 5 figures, minor changes to match published version