WIMPs during reheating

Weakly Interacting Massive Particles (WIMPs) are among the best-motivated dark matter candidates. In the standard scenario where the freeze-out happens well after the end of inflationary reheating, they are in tension with the severe experimental constraints. Here, we investigate the thermal freeze-out of WIMPs occurring during reheating, while the inflaton 0 coherently oscillates in a generic potential cx On. Depending on the value of n and the spin of the inflaton decaying products, the evolution of the radiation and inflaton energy densities can show distinct features, therefore, having a considerable impact on the freeze-out behavior of WIMPs. As a result of the injection of entropy during reheating, the parameter space compatible with the observed DM relic abundance is enlarged. In particular, the WIMP thermally averaged annihilation cross-section can be several magnitudes lower than that in the standard case. Finally, we discuss the current bounds from dark matter indirect detection experiments, and explore future challenges and opportunities.

Automated summary

This study investigates the impact of the evolution of radiation and inflaton energy densities on the freeze-out behavior of Weakly Interacting Massive Particles (WIMPs) during reheating. The researchers find that the injection of entropy during reheating enlarges the parameter space compatible with the observed dark matter relic abundance, and the thermally averaged annihilation cross-section of WIMPs can be significantly lower than in the standard case.