IMPLICATIONS OF A HEAVY TOP IN SUPERSYMMETRIC THEORIES

In the context of the radiative electroweak symmetry breaking scenario , we investigate the implications of a heavy top quark mass, close to its infrared fixed point, on the low energy parameters of the minimal supersymmetric standard model. We use analytic expressions to calculat e the Higgs masses as well as the supersymmetric masses of the third g eneration. We further assume bottom-tau unification at the GUT scale a nd examine the constraints put by this condition on the parameter spac e (tan beta,alpha(3)), using the renormalization group procedure at th e two-loop level. For supersymmetry breaking scale varying in the rang e (250-1000) GeV we find only a small fraction of the parameter space where the above conditions can be satisfied, namely 1 less than or equ al to tan beta less than or equal to 2, while 0.114 less than or equal to alpha(3)(M(z)) less than or equal to 0.125. We further analyse in brief the case where all three Yukawa couplings reach the perturbative limit just after the unification scale. In this case, due to the larg e corrections on the bottom mass from sparticle loops, the top-mass an d tan beta predictions are significantly lower than those estimated wh en such corrections were ignored.