Long-lived charged Higgs at LHC as a probe of scalar dark matter

We study inert charged Higgs boson H-+/- production and decays at LHC experiments in the context of constrained scalar dark matter model (CSDMM). In the CSDMM the mass spectrum of the inert doublet and singlet scalars is predicted from the GUT scale initial conditions via RGE evolution. We compute the cross sections of processes pp -> H+H-, (HSi0)-S-+/-, where S-i(0) are neutral scalar particles, at the LHC experiments. We show that for light H-+/- the first process may receive a sizable contribution from the top quark mediated 1-loop diagram with Higgs boson in s-channel. In a significant fraction of the parameter space H-+/- are long-lived because their decays to predominantly singlet scalar dark matter (DM) and next-to-lightest (NL) scalar, H-+/- -> S(DM, NL)ff', are suppressed by the small singlet-doublet mixing angle and by the moderate mass difference Delta M = MH+ - M-DM. The experimentally measurable displaced vertex in H-+/- decays to leptons and/or jets and missing energy allows one to discover the H+H- signal over the huge W+W- background. If, however, H-+/- are short-lived, the subsequent decays S-NL -> S(DM)f (f) over bar necessarily produce additional displaced vertices that allow to reconstruct the full H-+/- decay chain. We propose benchmark points for studies of this scenario at the LHC.