Production Regimes for Self-Interacting Dark Matter

TL;DR

This paper explores non-thermal production mechanisms for self-interacting dark matter, identifying regimes that satisfy observational constraints and differ from traditional thermal scenarios.

Contribution

It analyzes dark matter production via freeze-in, reannihilation, and dark freeze-out in a simple model, highlighting regimes compatible with constraints.

Findings

Dark freeze-out with 3-to-2 annihilations can satisfy constraints.

Freeze-in via a light mediator can also meet observational bounds.

Different temperatures in sectors help evade structure formation constraints.

Abstract

In the context of Self-Interacting Dark Matter as a solution for the small-scale structure problems, we consider the possibility that Dark Matter could have been produced without being in thermal equilibrium with the Standard Model bath. We discuss one by one the following various dark matter production regimes of this kind: freeze-in, reannihilation and dark freeze-out. We exemplify how these mechanisms work in the context of the particularly simple Hidden Vector Dark Matter model. In contrast to scenarios where there is thermal equilibrium with the Standard Model bath, we find two regimes which can easily satisfy all the laboratory and cosmological constraints. These are dark freeze-out with 3-to-2 annihilations and freeze-in via a light mediator. In the first regime, different temperatures in the visible and the Dark Matter sectors allow us to avoid the constraints coming from cosmic structure formation as well as the use of non-perturbative couplings to reproduce the observed relic density. For the second regime, different couplings are responsible for Dark Matter relic density and self-interactions, permitting to surpass BBN, X-ray, CMB and direct detection constraints.