# A Cosmic Selection Rule for Glueball Dark Matter Relic Density

## TL;DR

This paper proposes a mechanism where glueball dark matter relic density is determined by a cosmic selection rule involving early universe dynamics, dark sector confinement, and entropy sharing, largely independent of initial conditions.

## Contribution

It introduces a novel cosmic selection rule linking dark sector parameters to relic density, based on vectorlike quark dynamics and dark confinement.

## Key findings

- Relic density depends mainly on dark confinement scale and number of dark colors.
- The mechanism is largely insensitive to initial vectorlike quark abundance.
- Entropy sharing between sectors sets the final dark matter abundance.

## Abstract

We point out a unique mechanism to produce the relic abundance for glueball dark matter from a gauged $SU(N)_d$ hidden sector which is bridged to the standard model sector through heavy vectorlike quarks colored under gauge interactions from both sides. A necessary ingredient of our assumption is that the vectorlike quarks, produced either thermally or non-thermally, are abundant enough to dominate the universe for some time in the early universe. They later undergo dark color confinement and form unstable vectorlike-quarkonium states which annihilate decay and reheat the visible and dark sectors. The ratio of entropy dumped into two sectors and the final energy budget in the dark glueballs is only determined by low energy parameters, including the intrinsic scale of the dark $SU(N)_d$, $\Lambda_d$, and number of dark colors, $N_d$, but depend weakly on parameters in the ultraviolet such as the vectorlike quark mass or the initial condition. We call this a cosmic selection rule for the glueball dark matter relic density.