Cogenerating and pre-annihilating dark matter by a new gauge interaction in a unified model

Grand unified theories based on large groups (with rank >= 6) are a natural context for dark matter models. They contain Standard-Model-singlet fermions that could be dark matter candidates, and can contain new non-abelian interactions whose sphalerous convert baryons, leptons, and dark matter into each other, "cogenerating" a dark matter asymmetry comparable to the baryon asymmetry. In this paper it is shown that the same non-abelian interactions can "pre-annihilate" the symmetric component of heavy dark matter particles chi, which then decay late into light stable dark matter particles zeta that inherit their asymmetry. We derive cosmological constraints on the parameters of such models. The mass of chi must be < 3000 TeV and their decays must happen when 2 x 10(-7) < T-dec/m(chi) < 10(-4) is shown that such decays can come from d = 5 operators with coefficients of order 1/M-GUT try or 1/M-Pl. We present a simple realization of our model based on the group SU(7).