Lepton flavor violating decays of Higgs bosons beyond the standard model

Abstract

We evaluate the lepton flavor violating (LFV) decays of Higgs bosons $\stackrel{\ensuremath{\rightarrow}}{H}{l}_{i}^{+}{l}_{j}^{\ensuremath{-}}$ in several extensions of the standard model (SM), including both the effective Lagrangian approach and several specific models. Within the effective Lagrangian case, we focus on the dimension-6 operators that induce LFV vertices for the Higgs and Z bosons. For those operators whose coefficients cannot be constrained by present data, we estimate a branching ratio (B.R.) of the order of ${10}^{\ensuremath{-}1}\ensuremath{-}{10}^{\ensuremath{-}2}$ for the LFV Higgs boson decays, which can be detected at future hadron colliders. For the other operators that are bounded by current limits on the LFV transition, there are strong bounds on $e\ensuremath{-}\ensuremath{\mu}$ transitions, which imply $\mathrm{B}.\mathrm{R}.(\stackrel{\ensuremath{\rightarrow}}{H}e\ensuremath{\mu})\ensuremath{\simeq}{10}^{\ensuremath{-}9};$ however, even in this case the decay modes $\stackrel{\ensuremath{\rightarrow}}{H}\ensuremath{\tau}\ensuremath{\mu}/\ensuremath{\tau}e$ are allowed to have a B.R. of the order ${10}^{\ensuremath{-}1}.$ In the case of the general two-Higgs-doublet model, we also obtain $\mathrm{B}.\mathrm{R}.(\stackrel{\ensuremath{\rightarrow}}{H}\ensuremath{\tau}\ensuremath{\mu}/\ensuremath{\tau}e)\ensuremath{\simeq}{10}^{\ensuremath{-}1},$ whereas for the SM with massive neutrinos and the minimal supersymmetric-SM, the B.R.'s of the corresponding LFV Higgs decays are strongly suppressed.