Toward (Finally!) Ruling Out Z and Higgs Mediated Dark Matter Models
  In recent years, direct detection, indirect detection, and collider
experiments have placed increasingly stringent constraints on particle dark
matter, exploring much of the parameter space associated with the WIMP
paradigm. In this paper, we focus on the subset of WIMP models in which the
dark matter annihilates in the early universe through couplings to either the
Standard Model $Z$ or the Standard Model Higgs boson. Considering fermionic,
scalar, and vector dark matter candidates within a model-independent context,
we find that the overwhelming majority of these dark matter candidates are
already ruled out by existing experiments. In the case of $Z$ mediated dark
matter, the only scenarios that are not currently excluded are those in which
the dark matter is a fermion with an axial coupling and with a mass either
within a few GeV of the $Z$ resonance ($m_{\rm DM} \simeq m_Z/2$) or greater
than 200 GeV, or with a vector coupling and with $m_{\rm DM} > 6$ TeV. Several
Higgs mediated scenarios are currently viable if the mass of the dark matter is
near the Higgs pole ($m_{\rm DM} \simeq m_H/2$). Otherwise, the only scenarios
that are not excluded are those in which the dark matter is a scalar (vector)
heavier than 400 GeV (1160 GeV) with a Higgs portal coupling, or a fermion with
a pseudoscalar (CP violating) coupling to the Standard Model Higgs boson. With
the exception of dark matter with a purely pseudoscalar coupling to the Higgs,
it is anticipated that planned direct detection experiments will probe nearly
the entire range of models considered in this study.
