HIGGS AND SUPERSYMMETRIC PARTICLE SIGNALS AT THE INFRARED FIXED-POINTOF THE TOP-QUARK MASS

We study the properties of the Higgs and supersymmetric particle spect rum, associated with the infrared fixed point solution of the top quar k mass in the Minimal Supersymmetric Standard Model. We concentrate on the possible detection of these particles, analysing the deviations f rom the Standard Model predictions for the leptonic and hadronic varia bles measured at LEP and for the b --> s gamma decay rate. We consider the low and moderate tan beta regime, imposing the constraints derive d from a proper radiative SU(2)(L) X U(1)(Y) symmetry breaking, and we study both the cases of universal and non-universal soft supersymmetr y-breaking parameters at high energies. In the first case, for any giv en value of the top quark mass, the Higgs and supersymmetric particle spectrum is completely determined as a function of only two soft super symmetry-breaking parameters, implying very definite experimental sign atures. In the case of non-universal mass parameters at M(GUT), instea d, the strong correlations between the sparticle masses are relaxed, a llowing a richer structure for the precision data variables. As a gene ral feature, whenever a significant deviation from the Standard Model value of the precision data parameters is predicted, a light sparticle , which should be visible at LEP2, appears in the model.