Asymmetric dark matter

We consider a simple class of models in which the relic density of dark matter is determined by the baryon asymmetry of the Universe. In these models a $B\ensuremath{-}L$ asymmetry generated at high temperatures is transferred to the dark matter, which is charged under $B\ensuremath{-}L$. The interactions that transfer the asymmetry decouple at temperatures above the dark matter mass, freezing in a dark matter asymmetry of order the baryon asymmetry. This explains the observed relation between the baryon and dark matter densities for the dark matter mass in the range 5--15 GeV. The symmetric component of the dark matter can annihilate efficiently to light pseudoscalar Higgs particles $a$ or via $t$-channel…