Thermal Dark Matter with Low-Temperature Reheating

TL;DR

This paper investigates how low-temperature cosmic reheating affects the production and properties of various thermal dark matter candidates, revealing expanded viable parameter spaces and potential for future experimental constraints.

Contribution

It provides a model-independent analysis of dark matter freeze-out during low-temperature reheating, extending the viable mass and coupling ranges for multiple dark matter candidates.

Findings

Low-temperature reheating allows heavier dark matter particles than traditional models.

Current experiments already constrain some of the expanded parameter space.

Future experiments can further test these low-reheating scenarios.

Abstract

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.