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# WIMPs during Reheating

Nicolás Bernal and Yong Xu

Submitted on 15 September 2022

## Abstract

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 {\it during} reheating, while the inflaton $\varphi$ coherently oscillates in a generic potential $\propto {\varphi }^{n}$. 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.

## Preprint

Comment: 19 pages, 5 figures

Subjects: High Energy Physics - Phenomenology; Astrophysics - Cosmology and Nongalactic Astrophysics