LIGHT GLUINOS AND UNIFICATION OF COUPLINGS

We analyze the implications of the light gluino scenario for the unifi cation of gauge and Yukawa couplings within the minimal supersymmetric standard model. Within this scheme all fermionic supersymmetric parti cles are naturally light, while the scalar partners of quarks and lept ons, together with the heavy Higgs doublet may be heavy. This implies both a bound on tan beta < 2.3, in order to fulfill the experimental c onstraints on the chargino masses, and a strong correlation between si n2 theta(W) (M(Z)) and alpha3 (M(Z)), due to the suppression of the su persymmetric threshold corrections to the low energy values of the gau ge couplings. Assuming the scalar sparticles to be lighter than 10 TeV , the physical top quark mass is constrained to be 145 GeV < M(t) < 21 0 GeV for tan beta > 1, while the strong gauge coupling values, 0.122 less-than-or-equal-to alpha3 (M(Z)) less-than-or-equal-to 0.133, are i n good agreement with the measured LEP ones. We also show that a relax ation of some of the conventional assumptions is necessary in order to achieve the radiative breaking of the electroweak symmetry within the grand unification scheme.