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 couplings in terms of the universal gaugino mass m1/2, 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.