Dark matter relic density in strongly interacting dark sectors with light vector mesons

Stable dark matter particles may arise as pseudo-Goldstone bosons from the confinement of dark quarks interacting via a non-Abelian gauge force. Their relic abundance is determined not by annihilations into visible particles but by dark pion number-changing processes within the dark sector, such as $3⁢𝜋_𝐷→2⁢𝜋_𝐷$. However, if the dark vector mesons $𝜌_𝐷$ are light enough for $3⁢𝜋_𝐷→𝜋_𝐷⁢𝜌_𝐷$ annihilations to be kinematically allowed, this process dominates and significantly delays freeze-out. As a result, the preferred dark matter mass scale increases and bounds from the Bullet Cluster can be evaded.