ELECTROWEAK SUPERSYMMETRIC QUANTUM CORRECTIONS TO THE TOP-QUARK WIDTH

Within the framework of the MSSM, we compute the electroweak one-loop supersymmetric quantum corrections to the width GAMMA(t --> W+b) of th e canonical main decay of the top quark. The results are presented in two on-shell renormalization schemes parametrized either by alpha or G (F). While in the Standard Model, and in the Higgs sector of the MSSM, the electroweak radiative corrections in the G(F)-scheme are rather i nsensitive to the top quark mass and are of order of 1% at most, the r est (''genuine'' part) of the supersymmetric quantum effects in the MS SM amount to a non-negligible correction that could be about one order of magnitude larger, depending on the top quark mass and of the regio n of the supersymmetric parameter space. These new electroweak effects , therefore, could be of the same order (and go in the same direction) as the conventional leading QCD corrections.