Combined Fit of Low Energy Constraints to Minimal Supersymmetry and Discovery Potential at LEP II

Abstract

Within the Constrained Minimal Supersymmetric Standard Model it is possible to predict the low energy gauge couplings and masses of the 3. generation particles from a few parameters at the GUT scale. In addition the MSSM predicts elektroweak symmetry breaking due to large radiative corrections from Yukawa couplings, thus relating the Z^0 boson mass to the top quark mass. From a \chi^2 analysis, in which these constraints can be considered simultaneously, one can calculate the probability for each point in the MSGUT parameter space. Our fits include full second order corrections for the gauge and Yukawa couplings, low energy treshold effects, contributions of all (s)particles to the Higgs potential and corrections to m_b from qluinos and higgsinos, which exclude (in our notation) positive values of the mixing parameter in the Higgs potential \mu for the large tan \beta region. Further constraints can be derived from the branching ratio for the radiative (penguin) decay of the b-quark into s \gamma and the lower limit on the lifetime of the universe, which requires the dark matter density due to the Lightest Supersymmetric Particle (LSP) not to overclose the universe. For particles, which are most likely to have masses in the LEP II energy range, the cross sections are given for the various energy scenarios at LEP II. For low tan \beta the production of the lightest Higgs boson, which is expected to have a mass below 103 GeV, is the most promising channel, while for large tan \beta the production of charginos and/or neutralinos covers the preferred parameter space.