Thermal Dark Matter with Low-Temperature Reheating

We explore the production of thermal dark matter (DM) candidates (WIMPs, SIMPs, ELDERs and Cannibals) during cosmic reheating.

Assuming a general parametrization for the scaling of the inflaton energy density and the standard model (SM) temperature, we study the requirements for kinetic and chemical DM freeze-out in a model-independent way.

For each of the mechanisms, up to two solutions that fit the entire observed DM relic density exist, for a given reheating scenario and DM mass.

As an example, we assume a simple particle physics model in which DM interacts with itself and with SM through contact interactions.

We find that low-temperature reheating can accommodate a wider range of couplings and larger masses than those permitted in the usual instantaneous high-temperature reheating.

This results in DM solutions for WIMPs reaching masses as high as $10^{14}$~GeV, whereas for SIMPs and ELDERs, we can reach masses of $10^{13}$~GeV.

Interestingly, current experimental data already constrain the enlarged parameter space of these models with low-reheating temperatures.

Next-generation experiments could further probe these scenarios.

;Comment: 34 pages, 16 figures, To appear in JCAP