TOP QUARK MASS FROM RADIATIVE-CORRECTIONS TO THE Z-]BBBAR DECAY

The one-loop correction to the ZbbBAR vertex presents a quadratic dependence on the top-quark mass, which has its origin in the spontaneous symmetry breaking mechanism of the Standard Model. We study the possibility of fixing the top mass by comparing LEP measurements with theoretical predictions. Using the MSBAR renormalization scheme, we calculate the top mass dependence of the ZbbBAR vertex. For all Z-widths, we give simple approximate formulae which work at the 0.05% level. It is found that if some branching ratios involving the b-quark are measured at the 0.5% level the top mass will be determined with an error of 30 GeV using only LEP1 experiments.