Self-interacting dark matter without prejudice

TL;DR

This paper explores self-interacting dark matter models without relying on specific production mechanisms or early universe assumptions, revealing viable parameter space with a meta-stable light mediator that suggests new search strategies.

Contribution

It demonstrates that significant parameter space for self-interacting dark matter remains viable without assumptions about early universe conditions or production mechanisms.

Findings

Viable parameter space exists for dark matter with self-interactions mediated by a light vector.

Current observational data do not exclude models with a meta-stable light mediator.

Modified search strategies are needed for detecting such dark matter scenarios.

Abstract

The existence of dark matter particles that carry phenomenologically relevant self-interaction cross sections mediated by light dark sector states is considered to be severely constrained through a combination of experimental and observational data. The conclusion is based on the assumption of specific dark matter production mechanisms such as thermal freeze-out together with an extrapolation of a standard cosmological history beyond the epoch of primordial nucleosynthesis. In this work, we drop these assumptions and examine the scenario from the perspective of the current firm knowledge we have: results from direct and indirect dark matter searches and cosmological and astrophysical observations, without additional assumptions on dark matter genesis or the thermal state of the very early universe. We show that even in the minimal set-up, where dark matter particles self-interact via a kinetically mixed vector mediator, a significant amount of parameter space remains allowed. Interestingly, however, these parameter regions imply a meta-stable, light mediator, which in turn calls for modified search strategies.