Determination of the Effective Electroweak Mixing Angle from Z-Decays

Abstract The effective electroweak mixing angle sin 2 θ w is measured from the production and decay of the Z boson in e + e − interactions. The data sample corresponds to an integrated luminosity of 18pb −1 with about 420 000 hadronic and 40 000 leptonic Z decays. The mixing angle sin 2 θ w is determined from several independent measurements: the leptonic and hadronic cross sections, the forward-backward asymmetries of charged leptons and b-quarks, and the τ-polarization. The results are found to be in good agreement with each other. The value of sin 2 θ w from a fit to the asymmetries in a model independent method is 0.2321±0.0021 and from a global fit to the data in the Standard Model framework is 0.2328±0.0013.