Higgs $\rightarrow$ $\mu\tau$ as an indication for $S_4$ flavor symmetry

TL;DR

This paper proposes an $S_4$ three-Higgs-doublet model that explains the CMS excess in Higgs to mu-tau decays and predicts observable rates for other lepton flavor violating Higgs decays, linking flavor symmetry to experimental signals.

Contribution

It introduces an $S_4$ flavor symmetry model with three Higgs doublets that suppresses flavor-changing neutral currents and explains the CMS mu-tau excess through small symmetry breaking.

Findings

Explains CMS mu-tau excess with light neutral scalars.

Predicts sizable rates for e-tau and e-mu Higgs decays.

Suppresses unwanted flavor-changing neutral currents.

Abstract

Lepton flavor violating Higgs decays can arise in flavor symmetry models where the Higgs sector is responsible for both the electroweak and the flavor symmetry breaking. Here we advocate an $S_4$ three-Higgs-doublet model where tightly constrained flavor changing neutral currents are suppressed by a remnant $Z_3$ symmetry. A small breaking of this $Z_3$ symmetry can explain the $2.4\,\sigma$ excess of Higgs decay final states with a $\mu \tau $ topology reported recently by CMS if the new neutral scalars are light. The model also predicts sizable rates for lepton flavor violating Higgs decays in the $e\tau $ and $e \mu$ channels because of the unifying $S_4$ flavor symmetry.