Observing the dark scalar doublet and its impact on the standard-model Higgs boson at colliders

If the standard model of particle interactions is extended to include a second scalar doublet H^+, (H^0+iA^0) /2, which is odd under an unbroken Z₂ discrete symmetry, it may be called the dark scalar doublet, because its lightest neutral member, say H^0, is one possible component for the dark matter of the Universe. We discuss the general phenomenology of the four particles of this doublet, without assuming that H^0 is the dominant source of dark matter. We also consider the impact of this dark scalar doublet on the phenomenology of the standard-model Higgs boson h.