Simplified Models of Mixed Dark Matter
  We explore simplified models of mixed dark matter (DM), defined here to be a
stable relic composed of a singlet and an electroweak charged state. Our setup
describes a broad spectrum of thermal DM candidates that can naturally
accommodate the observed DM abundance but are subject to substantial
constraints from current and upcoming direct detection experiments. We identify
"blind spots" at which the DM-Higgs coupling is identically zero, thus
nullifying direct detection constraints on spin independent scattering.
Furthermore, we characterize the fine-tuning in mixing angles, i.e.
well-tempering, required for thermal freeze-out to accommodate the observed
abundance. Present and projected limits from LUX and XENON1T force many thermal
relic models into blind spot tuning, well-tempering, or both. This simplified
model framework generalizes bino-Higgsino DM in the MSSM, singlino-Higgsino DM
in the NMSSM, and scalar DM candidates that appear in models of extended Higgs
sectors.
