Generating the Dark Matter mass from the QCD vacuum: A new approach to the Dark Matter-Baryon coincidence problem

Abstract

The comparable abundances of dark matter and baryons imply a deep connection between the dark sector and the QCD sector. In models of asymmetric dark matter, the number densities of both sectors are ensured to be similar. However, a complete solution should also include a mechanism for comparable masses. In this letter, we present a solution based on a strongly coupled chiral dark sector, featuring a light composite fermion as the dark matter. Its mass is generated through the misalignment triggered by the QCD vacuum, ensuring the mass to be at the GeV scale. The model features $\mathcal{O}(1)$ GeV dark baryon dark matter together with dark pions (axion-like particles). Moreover, a composite QCD axion naturally arise in the UV model.