Charged Higgs Boson Phenomenology in the Dark Z mediated Fermionic Dark Matter Model

Abstract

We present the phenomenology of the charged Higgs boson $H^\pm$ appearing in a fermionic dark matter model mediated by an additional scalar doublet. In order to couple the dark matter fermion to the scalar doublet, we introduce a U(1)$_X$ gauge symmetry, which is spontaneously broken at electroweak symmetry breaking, resulting in a massive $Z'$ gauge boson. Since $Z'$ is generically light, the model is subject to strong constraints from electroweak precision observables. As a result, the charged Higgs boson mass allowed by current experimental bounds is typically light in this model, 110 GeV $<m_{H^\pm}<$ 170 GeV. Such a light charged Higgs boson will be produced mainly through top-quark decays at the LHC. Additionally, depending on the mass of the additional neutral Higgs boson $h$ and the dark gauge boson $Z'$, the direct production channels $pp \to H^\pm Z'$ and $pp \to H^\pm h$ can become sizable. We investigate the corresponding signal processes at the LHC to assess the discovery potential for $H^\pm$. Current ATLAS and CMS searches for light charged Higgs bosons already impose further constraints on the model. We also discuss the implications of dark matter in relation to the charged Higgs boson phenomenology.