Two hidden scalars around 125 GeV andh→μτ

Abstract

We show that the 2.4σ signal of the leptonic flavor violating (LFV) Higgs boson decay h→μτ, as observed by the CMS Collaboration recently, can be explained by a certain class of two-Higgs doublet models that allow controllable flavor-changing neutral current with a minimal number of free parameters. We postulate that (i) the alignment limit is maintained, which means the lightest neutral scalar (h) has identical couplings to that of the Standard Model Higgs boson and (ii) the signal comes from two other neutral scalars, the CP-even H and the -odd A, almost degenerate with h at 125 GeV. We also show that (i) it is entirely possible that these scalars are hidden, apart from this LFV signal; (ii) the signal strengths of bb¯, τ+τ- and γγ around 125 GeV put severe constraints on the parameter space of such models; (iii) the constraint is further enhanced by the nonobservation of processes like μ→eγ, and we predict that the branching ratio of μ→eγ cannot be even an order below the present experimental limit, highlighting the role it plays in forcing H and A to be near-degenerate; (iv) an enhancement in the τ+τ- production cross section at around 125 GeV is expected in the gluon fusion channel, and should be observed during the next run of the LHC; (v) the branching ratio in the eτ channel is enhanced and is expected to be at least about 2%. The constrained parameter space and minimum number of free parameters, along with such strong predictions, make this model easily testable and falsifiable. (Less)