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

Abstract

Within the Constrained Minimal Supersymmetric Standard Model (CMSSM) 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, and electroweak symmetry breaking. 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. 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. The recently measured top quark mass prefers two solutions for the mixing angle in the Higgs sector: tan beta in the range between 1 and 3 or alternatively tan beta approx 25-50. For both cases we find a unique chi^2 minimum in the parameter space. For the low tan beta solution these additional constraints can be fulfilled simultaneously for quite a large region of the parameter space. In contrast, for the high tan beta solution the correct value for the b --> s gamma rate is obtained only for small values of the gaugino scale. 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. The highest LEP II energies (205 GeV) are just high enough to cover a large region of the preferred parameter space, both for the low and high tan beta solutions. For low tan beta the production of the lightest Higgs boson, which is expected to have a mass below 115 GeV, is the most promising channel, while for large tan beta the production of charginos and/or neutralinos covers the preferred parameter space.