From WIMPs to FIMPs: Impact of Early Matter Domination

TL;DR

This paper investigates how an early matter-dominated era in non-standard cosmologies affects dark matter production, revealing a continuous WIMP-FIMP transition and expanding the viable parameter space for detection.

Contribution

It demonstrates how early matter domination alters dark matter genesis, enabling a unified WIMP-FIMP framework and broadening experimental prospects.

Findings

EMD modifies Hubble rate and entropy, impacting DM production.

WIMP couplings can be smaller, FIMP couplings larger than in standard cosmology.

Results applicable to various DM models, expanding detection possibilities.

Abstract

In the context of non-standard cosmologies, an early matter-dominated (EMD) era can significantly alter the conventional dark matter (DM) genesis. In this work, we reexamine the impact of an EMD on the weakly- and feebly-interacting massive particle (WIMP and FIMP) paradigms. EMD eras significantly modify the genesis of DM because of the change in the Hubble expansion rate and the injection of entropy. The WIMP paradigm can be realized with couplings much smaller than in the standard cosmological scenario, whereas much larger couplings are required in the FIMP case. Using the singlet-scalar DM model as a case study, we show that these results can lead to a continuous transition between the WIMP and FIMP scenarios, with results that are also applicable to other DM models. This broadens the parameter space consistent with observed DM levels and suggests that even elusive FIMP scenarios may be within the reach of future experimental searches.