# Conversion-driven freeze-out: Dark matter genesis beyond the WIMP paradigm

## TL;DR

This paper explores a novel dark matter production mechanism called conversion-driven freeze-out, where dark matter's relic abundance is set by conversion processes within a dark sector, rather than traditional self-annihilation.

## Contribution

It introduces and analyzes the conversion-driven freeze-out scenario, expanding the understanding of dark matter genesis beyond the standard WIMP paradigm.

## Key findings

- Conversion-driven freeze-out can produce the correct dark matter relic abundance.
- This scenario involves chemical equilibrium maintained by conversion processes, not annihilation.
- Distinct phenomenological signatures differentiate it from traditional WIMP models.

## Abstract

We consider dark matter (DM) with very weak couplings to the standard model (SM), such that its self-annihilation cross section is much smaller than the canonical one, $\langle\sigma v\rangle_{\chi\chi} \ll 10^{-26}\mathrm{cm}^3/\mathrm{s}$. In this case DM self-annihilation is negligible for the dynamics of freeze-out and DM dilution is solely driven by efficient annihilation of heavier accompanying dark sector particles provided that DM maintains chemical equilibrium with the dark sector. This chemical equilibrium is established by conversion processes which require much smaller couplings to be efficient than annihilation. The chemical decoupling of DM from the SM can either be initiated by the freeze-out of annihilation, resembling a co-annihilation scenario, or of conversion processes, leading to the scenario of conversion-driven freeze-out. We focus on the latter and discuss its distinct phenomenology.