Dark Matter and the Baryon Asymmetry of the Universe

We present a mechanism to generate the baryon asymmetry of the Universe which preserves the net baryon number created in the big bang. If dark matter particles carry baryon number BX, and σX̄ᵃⁿⁿⁱʰ<σXᵃⁿⁿⁱʰ, the X̄'s freeze-out at a higher temperature and have a larger relic density than X's. If mX4.5BX GeV and the annihilation cross sections differ by O(10%) or more, this type of scenario naturally explains the observed ΩDM≈5Ωb.