Implications of the Muon g-2 result on the flavour structure of the lepton mass matrix

TL;DR

This paper explores how the recent Muon g-2 anomaly impacts the understanding of lepton flavor symmetries and constrains models of the lepton mass matrix, linking experimental results with flavor symmetry structures.

Contribution

It analyzes the implications of the Muon g-2 result on low-energy flavor symmetries and their role in shaping the lepton mass matrix, focusing on discrete symmetry models.

Findings

Flavor symmetries can explain the Muon g-2 discrepancy.

Lepton flavor violating processes constrain flavor symmetry models.

Specific discrete symmetries like Δ(27), A4, and A5×CP are examined.

Abstract

The confirmation of the discrepancy with the Standard Model predictions in the anomalous magnetic moment by the Muon g-2 experiment at Fermilab points to a low scale of new physics. Flavour symmetries broken at low energies can account for this discrepancy but these models are much more restricted, as they would also generate off-diagonal entries in the dipole moment matrix. Therefore, if we assume that the observed discrepancy in the muon $g-2$ is explained by the contributions of a low-energy flavor symmetry, lepton flavour violating processes can constrain the structure of the lepton mass matrices and therefore the flavour symmetries themselves predicting these structures. We apply these ideas to several discrete flavour symmetries popular in the leptonic sector, such as $\Delta (27)$, $A_4$, and $A_5 \ltimes {\rm CP}$.