A DETERMINATION OF THE ZB(B)OVER-BAR VERTEX CORRECTION FROM LEP DATA

Using recent LEP measurements of the ratios of Z bosons widths GAMMA(Z --> bbBAR)/GAMMA(Z --> hadrons) and GAMMA(Z --> hadrons)/GAMMA(Z --> leptons), we determine the size of the vertex radiative correction to the Z --> bbBAR partial decay width. This allows, in the context of the minimal standard model, to set the 95% confidence level upper bound on the top quark mass, m(t) < 208 GeV independently of the Higgs boson mass. This value is remarkably close to the completely independent available bounds, which are extracted from the measurement of the radiative correction to the p parameter. The implication of possible New Physics on this measurement is briefly commented upon.