On thermal production of self-interacting dark matter

TL;DR

This paper explores how self-interacting dark matter can be thermally produced in models with gauged Z3 symmetry, highlighting the roles of dark photon and dark Higgs in the freeze-out process.

Contribution

It introduces a model with gauged Z3 symmetry for self-interacting dark matter and analyzes the thermal production mechanisms including SM-annihilation, SIMP, and forbidden channels.

Findings

Light dark photon and dark Higgs are necessary for unitarity.

Parameter space constraints depend on dominant production channels.

Multiple channels can influence the relic density of dark matter.

Abstract

We consider thermal production mechanisms of self-interacting dark matter in models with gauged $Z_3$ symmetry. A complex scalar dark matter is stabilized by the $Z_3$, that is the remnant of a local dark $U(1)_d$. Light dark matter with large self-interaction can be produced from thermal freeze-out in the presence of SM-annihilation, SIMP and/or forbidden channels. We show that dark photon and/or dark Higgs should be relatively light for unitarity and then assist the thermal freeze-out. We identify the constraints on the parameter space of dark matter self-interaction and mass in cases that one or some of the channels are important in determining the relic density.