Dark matter from strong dynamics: the minimal theory of dark baryons

As a simple model for dark matter, we propose a QCD-like theory based on 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 SU(2)_B, resembling isospin; and baryons and mesons are unified together in 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 η′ 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 → 2 cannibalizing transitions. We discuss some experimental implications of coupling dark baryons to the Higgs portal.