If the standard model of particle interactions is extended to include a second scalar doublet $[H^{+},(H^0+i{A}^0)/\sqrt{2}]$, which is odd under an unbroken $Z_2$ 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 $h$.

• Received 28 August 2007

DOI:https://doi.org/10.1103/PhysRevD.76.095011