Neutralino dark matter in a class of unified theories

The cosmological significance of the neutralino sector is studied for a class of supersymmetric grand unified theories in which electroweak symmetry breaking is seeded by a gauge singlet. Extensive use is made of the renormalization group equations to significantly reduce the parameter space, by deriving analytic expressions for all the supersymmetry-breaking coupling in terms of the universal gaugino mass m12, the universal scalar mass m0 and the coupling A. The composition of the lightest supersymmetric partner is determined exactly below the W-mass, no approximations are made for sfermion masses, and all particle exchanges are considered in calculating the annihilation cross section; the relic abundance is then obtained by an analytic approximation. We find that in these models, stable neutralinos may make a significant contribution to the dark matter in the universe.