Neutralino Relic Density with a Cosmological Constant confronts Electroweak Precision Measurements

Abstract

We discuss the relic density of the lightest of the supersymmetric particles ({\small LSP}) in view of new cosmological data, which favour the concept of an accelerating Universe with a non-vanishing cosmological constant. The new bound on the Cold Dark Matter density, $Ω_{\mathrm{CDM}} h_0^2 \lesssim 0.22$, puts stringent constraints on supersymmetry preferring low supersymmetry breaking scales, in sharp contrast to electroweak precision measurements favouring large supersymmetry breaking scales. Supersymmetric predictions are in agreement with cosmological data and electroweak precision data in the window of the parameter space: $m_0<200\GeV$, $300\GeV<M_{1/2}<400\GeV$, putting bounds on sparticle masses, which may be evaded if $m_{LSP} <m_{{\tildeτ}_R} \lesssim 1.2 m_{LSP}$.