New Constraints on Neutralino Dark Matter in the Supersymmetric Standard Model

Abstract

We investigate the prospects for neutralino dark matter within the Supersymmetric Standard Model (SSM) including the constraints from universal soft supersymmetry breaking and radiative breaking of the electroweak symmetry. The latter is enforced by using the one-loop Higgs effective potential which automatically gives the one-loop corrected Higgs boson masses. We perform an exhaustive search of the allowed five-dimensional parameter space and find that the neutralino relic abundance $Ω_χh^2_0$ depends most strongly on the ratio $ξ_0\equiv m_0/m_{1/2}$. For $ξ_0\gg1$ the relic abundance is almost always much too large, whereas for $ξ_0\ll1$ the opposite occurs. For $ξ_0\sim1$ there are wide ranges of the remaining parameters for which $Ω_χ\sim1$. We also determine that $m_{\tilde q}\gsim250\GeV$ and $m_{\tilde l}\gsim100\GeV$ are necessary in order to possibly achieve $Ω_χ\sim1$. These lower bounds are much weaker than the corresponding ones derived previously when radiative breaking was {\it not} enforced.