Higgs effects on the relic supersymmetric particle density

We explore in the minimal supersymmetric extension of the standard model the effects of Higgs exchange on the cosmological relic density ρ of the lightest supersymmetric particle (LSP), taking into account the constraints on the supersymmetric Higgs masses imposed by LEP. We find in general a significant enlargement of the region of parameter space in which ρ < ρ70=10-29 g cm-3, the closure density if the Hubble constant is 70 km s-1 Mpc-1. This effect is potentially important if the ratio of Higgs VEVs tan β=vt/vb≅2-4 as in many realistic models. The restricted region of parameter space in which closure density is obtained for a Hubble constant between 50 and 70 km s-1 Mpc-1 is particularly sensitive to the Higgs contribution. (orig.)