Thermal Squeezeout of Dark Matter

TL;DR

This paper investigates how a first-order confinement phase transition in a dark sector can lead to enhanced dark matter annihilation, allowing for heavier dark matter particles beyond the unitarity bound, largely independent of portal details.

Contribution

It provides a detailed analysis of dark matter production during a first-order confinement phase transition, revealing a new mechanism for heavier dark matter particles.

Findings

Dark matter can be heavier than 100 TeV due to enhanced annihilation during phase transition.

Dark matter abundance is significantly affected by the trapping and compression during the phase transition.

The results are largely independent of the portal interactions with the Standard Model.

Abstract

We carry out a detailed study of the confinement phase transition in a dark sector with a $SU(N)$ gauge group and a single generation of dark heavy quark. We focus on heavy enough quarks such that their abundance freezes out before the phase transition and the phase transition is of first-order. We find that during this phase transition the quarks are trapped inside contracting pockets of the deconfined phase and are compressed enough to interact at a significant rate, giving rise to a second stage of annihilation that can dramatically change the resulting dark matter abundance. As a result, the dark matter can be heavier than the often-quoted unitarity bound of $\sim100~$TeV. Our findings are almost completely independent of the details of the portal between the dark sector and the Standard Model. We comment briefly on possible signals of such a sector. Our main findings are summarized in a companion letter, while here we provide further details on different parts of the calculation.