New constraints on neutralino dark matter in the supersymmetric standard model

We investigate the prospects for neutralino dark matter within theSupersymmetric Standard Model (SSM) including the constraints from universalsoft supersymmetry breaking and radiative breaking of the electroweak symmetry.The latter is enforced by using the one-loop Higgs effective potential whichautomatically gives the one-loop corrected Higgs boson masses. We perform anexhaustive search of the allowed five-dimensional parameter space and find thatthe neutralino relic abundance $\Omega_\chi h^2_0$ depends most strongly on theratio $\xi_0\equiv m_0/m_{1/2}$. For $\xi_0\gg1$ the relic abundance is almostalways much too large, whereas for $\xi_0\ll1$ the opposite occurs. For$\xi_0\sim1$ there are wide ranges of the remaining parameters for which$\Omega_\chi\sim1$. We also determine that $m_{\tilde q}\gsim250\GeV$ and$m_{\tilde l}\gsim100\GeV$ are necessary in order to possibly achieve$\Omega_\chi\sim1$. These lower bounds are much weaker than the correspondingones derived previously when radiative breaking was {\it not} enforced.Comment: 12 pages plus 6 figures (not included), CERN-TH.6584/92, CTP-TAMU-56/92, UAHEP921