Can the relic density of self-interacting dark matter be due to annihilations into Standard Model particles?

TL;DR

This paper explores whether the relic density of self-interacting dark matter can be explained by annihilations into Standard Model particles, identifying specific viable candidates and discussing future experimental tests.

Contribution

It demonstrates that scalar and Majorana dark matter in the 10-500 MeV range, coupled to a heavier gauge boson, can account for relic density consistent with experimental constraints.

Findings

Scalar and Majorana dark matter candidates are viable.

Annihilation rates are slower than self-interactions due to small coupling.

Future experiments can potentially confirm or exclude these scenarios.

Abstract

Motivated by the hypothesis that dark matter self-interactions provide a solution to the small-scale structure formation problems, we investigate the possibilities that the relic density of a self-interacting dark matter candidate can proceed from the thermal freeze-out of annihilations into Standard Model particles. We find that scalar and Majorana dark matter in the mass range of $10-500$ MeV, coupled to a slightly heavier massive gauge boson, are the only possible candidates in agreement with multiple current experimental constraints. Here dark matter annihilations take place at a much slower rate than the self-interactions simply because the interaction connecting the Standard Model and the dark matter sectors is small. We also discuss prospects of establishing or excluding these two scenarios in future experiments.