LEP electroweak parameter results

During 1990-1994 LEP was run at center-of mass energies near the Z peak and precise measurements of the beam energy have been performed. The LEP experiments ALEPH, DELPHI, L3 and OPAL have recorded more than 107 hadronic and leptonic decays of the Z. Results on hadronic and leptonic cross sections, leptonic forward-backward asymmetries and T polarization asymmetries are presented. They allow for a determination of the mass and the width of the Z boson: mz = 91.1887 ± 0.0022 GeV and fz = 2.4971 ± 0.0033 GeV. From all LEP asymmetry measurements a value of sin2B��t was derived: sin20�';1'' = 0.2318 ± 0.0004. Precise electroweak data are used to test the Standard Model prediction and, within its framework, to constrain the top quark mass to the value: m, = 179 ± 9 :!::�GeV which is in excellent agreement with the results from direct observation.