Measurement of the Z resonance parameters at LEP

The properties of the Z resonance are measured from the analysis of 4.5 million Z decays into fermion pairs collected with the ALEPII detector at LEP. The data are consistent with lepton universality. The resonance parameters are measured to be M-Z = (91.1885 +/- 0.0031) GeV/c(2), Gamma(Z) = (2.4941 +/- 0.0043) GeV, sigma(had)(0) = (41.559 +/- 0.058) nb and, combining the three lepton flavours, R-l = 20.725 +/- 0.039. The corresponding number of light neutrino species is N-v = 2.983 +/- 0.013 and the strong coupling constant is alpha(s)(M-Z) = 0.114 +/- 0.004 +/- 0.002(QCD) + 0.005 log(10) [M-H/150 GeV/c(2)]. The lepton pair forward-backward asymmetry is measured to be A(FB)(0,l) = 0.0173 +/- 0.0016 from which the effective weak mixing angle is described: sin(2) theta(eff)(lept) = 0.23089 +/- 0.00089. The measurement of the leptonic width Gamma(ll) = 84.02 +/- 0.15 MeV leads to a determination of the effective rho parameter rho(eff)(lept) = 1.0064 +/- 0.0018. The data support the Standard Model and favour a light Higgs.