A measurement of the Z0 leptonic partial widths and the vector and axial vector coupling constants

Abstract We have measured the partial widths of the Z 0 into leptonpairs, and the forward-backward charge asymmetry for the process e + e − → μ + μ − using the L3 detector at LEP. We obtain an average Γ ll of 83.0±2.1±1.1 MeV.From this result and the asymmetry measurement, we extract the values of the vector and axial vector couplings of the Z 0 to leptons: g rmv =−0.066 −0.027 +0.046 and g rmA = −0.495 −0.007 +0.007 .