Simplified dark matter models with charged mediators

Abstract

We review simplified models in which a singlet Majorana dark matter candidate couples to Standard Model (SM) fermions through interactions mediated by scalar fermion partners. We summarize the two primary production mechanisms in these scenarios: dark matter annihilation mediated by first or second generation scalar fermion partners with significant left-right chiral mixing and co-annihilation with scalar fermion partners nearly degenerate in mass with the dark matter. We then highlight the most interesting phenomenological aspects of charged mediator models relevant for current and future searches for new physics. We describe precision measurements of SM fermion dipole moments, including models with scalar muon partners that can account for $g_\mu-2$. We discuss new search strategies for charged mediators at the LHC and the projected sensitivity of future lepton colliders. We summarize constraints from direct detection and demonstrate how next generation experiments might probe QCD-charged mediators at mass scales beyond the sensitivity of the LHC. We also review the prospects for indirect detection of models with scalar lepton partners, focusing on the sensitivity of gamma-ray searches to internal bremsstrahlung emission.