Supersymmetric dark matter in the light of CERN LEP and the Fermilab Tevatron collider

Abstract

We analyze the accelerator constraints on the parameter space of the minimal supersymmetric extension of the standard model, comparing those now available from CERN LEP II and anticipating the likely sensitivity of Fermilab Tevatron run II. The most important limits are those from searches for charginos ${\ensuremath{\chi}}^{\ifmmode\pm\else\textpm\fi{}},$ neutralinos ${\ensuremath{\chi}}_{i}$ and Higgs bosons at LEP, and searches for top squarks, charginos and neutralinos at the Tevatron collider. We also incorporate the constraints derived from $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma}$ decay, and discuss the relevance of charge- and color-breaking minima in the effective potential. We combine and compare the different constraints on the Higgs-mixing parameter $\ensuremath{\mu},$ the gaugino-mass parameter ${m}_{1/2}$ and the scalar-mass parameter ${m}_{0},$ incorporating radiative corrections to the physical particle masses. We focus on the resulting limitations on supersymmetric dark matter, assumed to be the lightest neutralino $\ensuremath{\chi},$ incorporating coannihilation effects in the calculation of the relic abundance. We find that ${m}_{\ensuremath{\chi}}>51 \mathrm{GeV}$ and $\mathrm{tan}\ensuremath{\beta}>2.2$ if all soft supersymmetry-breaking scalar masses are universal, including those of the Higgs bosons, and that these limits weaken to ${m}_{\ensuremath{\chi}}>46 \mathrm{GeV}$ and $\mathrm{tan}\ensuremath{\beta}>1.9$ if nonuniversal scalar masses are allowed. Light neutralino dark matter cannot be primarily Higgsino in composition.