Interplay between improved interaction rates and modified cosmological histories for dark matter

TL;DR

This paper investigates how recent advances in particle interaction rates and alternative cosmological expansion histories jointly influence the predicted dark matter abundance, focusing on freeze-out and freeze-in mechanisms.

Contribution

It introduces the combined effects of updated particle physics processes and modified cosmological models on dark matter density predictions.

Findings

Enhanced annihilation due to Sommerfeld and bound-state effects.

Thermal masses can significantly alter dark matter yields.

Faster universe expansion impacts dark matter production.

Abstract

A novel particle has been and still is an intriguing option to explain the strong evidence for dark matter in our universe. To quantitatively predict the dark matter energy density, two main ingredients are needed: interaction rates and an expansion history of the universe. In this work, we explore the interplay between recent progress in the determination of particle production rates and modified cosmological histories. For the freeze-out mechanism, we focus on Sommerfeld and bound-state effects, which boost and make dark matter pair annihilation more efficient. As regards the freeze-in option, we include thermal masses, which enter the decay processes that produce dark matter, and we find that they can suppress or enhance the dark matter yield. We consider a class of modified cosmological histories that induce a faster universe expansion, and we assess their effect in combination with improved particle interaction rates on the dark matter energy density.