Improved measurements of electroweak parameters from $Z$ decays into fermion pairs

The properties of theZ resonance are measured on the basis of 190 000Z decays into fermion pairs collected with the ALEPH detector at LEP. Assuming lepton universality,M z =(91.182±0.009exp±0.020L∶P) GeV,Г Z =(2484±17) MeV, σ had 0 =(41.44±0.36) nb, andГ jad /Гll=21.00±0.20. The corresponding number of light neutrino species is 2.97±0.07. The forward-back-ward asymmetry in leptonic decays is used to determine the ratio of vector to axial-vector coupling constants of leptons:g v 2 (M Z 2 )/g A 2 (M Z 2 )=0.0072±0.0027. Combining these results with ALEPH results on quark charge and\(b\bar b\) asymmetries, and τ polarization, sin2θ W (M Z 2 ). In the contex of the Minimal Standard Model, limits are placed on the top-quark mass.