Flavor Violating Higgs Decays

TL;DR

This paper investigates flavor violating Higgs decays, showing they can be sizable and currently constrained by LHC data, offering a promising avenue for discovering new physics beyond the Standard Model.

Contribution

It provides updated constraints on flavor violating Higgs couplings and demonstrates that certain decay modes could be detectable with current or improved collider searches.

Findings

Flavor violating Higgs decays to leptons can have branching ratios around 10%.

Current LHC bounds on h -> tau mu and h -> tau e are stronger than rare decay constraints.

Dedicated searches can significantly improve the sensitivity to flavor violating Higgs decays.

Abstract

We study a class of nonstandard interactions of the newly discovered 125 GeV Higgs-like resonance that are especially interesting probes of new physics: flavor violating Higgs couplings to leptons and quarks. These interaction can arise in many frameworks of new physics at the electroweak scale such as two Higgs doublet models, extra dimensions, or models of compositeness. We rederive constraints on flavor violating Higgs couplings using data on rare decays, electric and magnetic dipole moments, and meson oscillations. We confirm that flavor violating Higgs boson decays to leptons can be sizeable with, e.g., h -> tau mu and h -> tau e branching ratios of order 10% perfectly allowed by low energy constraints. We estimate the current LHC limits on h -> tau mu and h -> tau e decays by recasting existing searches for the SM Higgs in the tau-tau channel and find that these bounds are already stronger than those from rare tau decays. We also show that these limits can be improved significantly with dedicated searches and we outline a possible search strategy. Flavor violating Higgs decays therefore present an opportunity for discovery of new physics which in some cases may be easier to access experimentally than flavor conserving deviations from the Standard Model Higgs framework.