Naturally large radiative lepton flavor violating Higgs decay mediated by lepton-flavored dark matter

Seungwon Baek,Zhaofeng Kang

doi:10.1007/jhep03(2016)106

Abstract

In the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and thus it is a good probe to new physics. In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by a Majorana DM and scalar lepton mediators. Different from other similar models with similar setup, we introduce both left-handed and right-handed scalar leptons. They allow large LFV Higgs decay and thus may explain the tentative Br$(h\ra\tau\mu)\sim1\%$ experimental results from the LHC. In particular, we find that the stringent bound from $\tau\ra\mu\gamma$ can be naturally evaded. One reason, among others, is a large chirality violation in the mediator sector. Aspects of relic density and especially radiative direct detection of the leptonic DM are also investigated, stressing the difference from previous lepton-flavored DM models.

Highlights

In the models with canonical seesaw mechanism lepton flavor violating (LFV) Higgs decay is too small to be observed [7, 8]
In the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and it is a good probe to new physics
In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by a Majorana DM and scalar lepton mediators

Summary

The model with dual mediators

A natural way to realize a lepton-flavored DM is to introduce a Majorana DM candidate connected to some lepton flavors by means of scalar leptons. In order to make up a lepton-flavored DM, one can designate a scalar partner for each SM left-handed lepton doublet lL and right-handed lepton signlet eR. They are labelled as φ and φe, respectively. The part involving the two Higgs doublets, as usual, is given by In this potential most parameters are irrelevant to our phenomenological studies, except for λ5 that is crucial in neutrino mass generation. In this paper we will not pay further attention on this aspect and always assume a sufficiently small λ5 to suppress radiative neutrino mass

The mass spectrum of the mediators

Annihilation: s-wave versus p-wave

Conclusion

A Two- and three-points scalar functions and their limits

Findings

B Radiative corrections on Higgs-DM-DM vertex