Hypercharged Dark Matter and Direct Detection as a Probe of Reheating

The lack of new physics at the LHC so far weakens the argument for TeV scale thermal dark matter. On the other hand, heavier, non-thermal dark matter is generally difficult to test experimentally. Here we consider the interesting and generic case of hypercharged dark matter, which can allow for heavy dark matter masses without spoiling testability. Planned direct detection experiments will be able to see a signal for masses up to an incredible $10^{10}$ GeV, and this can further serve to probe the reheating temperature up to about $10^9$ GeV, as determined by the non-thermal dark matter relic abundance. The $Z$-mediated nature of the dark matter scattering may be determined in principle by comparing scattering rates on different detector nuclei, which in turn can reveal the dark matter mass. We will discuss the extent to which future experiments may be able to make such a determination.