Fingerprints of freeze-in dark matter in an early matter-dominated era

TL;DR

This paper explores how an early matter-dominated epoch in the universe's history affects the freeze-in production of dark matter, allowing for larger couplings and providing testable predictions with dark photon models.

Contribution

It introduces a novel cosmological scenario with early matter domination impacting dark matter production, expanding the viable parameter space for freeze-in mechanisms.

Findings

Larger dark-visible sector couplings are possible in this scenario.

The model's parameter space can be tested by current experiments.

Early matter domination influences dark matter relic abundance calculations.

Abstract

We study the impact of an alternate cosmological history with an early matter-dominated epoch on the freeze-in production of dark matter. Such early matter domination is triggered by a meta-stable matter field dissipating into radiation. In general, the dissipation rate has a non-trivial temperature and scale factor dependence. Compared to the usual case of dark matter production via the freeze-in mechanism in a radiation-dominated universe, in this scenario, orders of magnitude larger coupling between the visible and the dark sector can be accommodated. Finally, as a proof of principle, we consider a specific model where the dark matter is produced by a sub-GeV dark photon having a kinetic mixing with the Standard Model photon. We point out that the parameter space of this model can be probed by the experiments in the presence of an early matter-dominated era.