Simple model of dark matter and CP violation

We propose a simple model of dark matter and CP violation and consider the associated triple and dark matter is a vectorlike dark fermion (????, ??) interacting with the Standard Model only through a complex messenger scalar S which is an electroweak singlet. New sources of CP violation reside in the most general scalar potential involving the doublet H and the singlet S, as well as in the dark Yukawa coupling between S and (????, ?? ). We study current experimental constraints from Higgs measurements, searches for new scalars at the LHC, precision electroweak measurements, EDM measurements, dark matter relic density, as well as direct and indirect detections of dark matter. A smoking-gun signature of CP violation could come from the Higgs-to-Higgs decays, h3 - h2h1, where h3/h2/h1 are the heaviest scalar, second heaviest scalar and the SM-like 125-GeV Higgs, respectively. Taking into account other Higgs-to-Higgs decays, such as h3 - 2h2 and h3/h2 - 2h1, then gives rise to novel 3h1 and 4h1 final states, which have yet to be searched for experimentally. We present four benchmarks and show the event rates for 3h1 and 4h1 final states could be as large as O(10) fb and O(1) fb, respectively, at the 14-TeV LHC. This work opens up a new frontier of searching for triple and quadruple Higgs bosons at a high energy collider.