Mono-$X$ signatures are a powerful collider probe of the nature of dark matter. We show that mono-Higgs and mono-$Z$ may be key signatures of pseudoscalar portal interactions between dark matter and the standard model. We demonstrate this using a simple renormalizable version of the portal, with a two-Higgs-doublet model as an electroweak symmetry breaking sector. Mono-$Z$ and mono-Higgs signatures in this scenario are of resonant type, which constitutes a novel type of dark matter signature at the LHC.

• Received 8 September 2015

DOI:https://doi.org/10.1103/PhysRevD.93.031701