Dark Matter from Strong Dynamics: The Minimal Theory of Dark Baryons

TL;DR

This paper introduces a minimal dark matter model based on an SU(2) gauge theory with one dark quark, exploring its properties via lattice simulations and proposing it as a candidate for stable dark matter with unique features.

Contribution

The paper presents a novel SU(2) gauge theory with one flavor as a dark matter model, analyzing its hadron spectrum and stability, and discusses its implications for dark matter phenomenology.

Findings

The lightest baryon is a stable vector boson dark matter candidate.

The theory exhibits no Goldstone bosons or chiral symmetry restoration at massless dark quark.

Dark matter can annihilate via an analog of the eta' state, affecting relic density.

Abstract

As a simple model for dark matter, we propose a QCD-like theory based on $\rm{SU}(2)$ gauge theory with one flavor of dark quark. The model is confining at low energy and we use lattice simulations to investigate the properties of the lowest-lying hadrons. Compared to QCD, the theory has several peculiar differences: there are no Goldstone bosons or chiral symmetry restoration when the dark quark becomes massless; the usual global baryon number symmetry is enlarged to $\rm{SU}(2)_B$, resembling isospin; and baryons and mesons are unified together in $\rm{SU}(2)_B$ iso-multiplets. We argue that the lightest baryon, a vector boson, is a stable dark matter candidate and is a composite realization of the hidden vector dark matter scenario. The model naturally includes a lighter state, the analog of the $\eta^\prime$ in QCD, for dark matter to annihilate into to set the relic density via thermal freeze-out. Dark matter baryons may also be asymmetric, strongly self-interacting, or have their relic density set via $3 \to 2$ cannibalizing transitions. We discuss some experimental implications of coupling dark baryons to the Higgs portal.