A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model
This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 2003 summer conferences. Averages from $\Zzero$ resonance results are derived for hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the $\tau$ polarisation asymmetries, the $\bb$ and $\cc$ partial widths and forward-backward asymmetries and the $\qq$ charge asymmetry. Above the $\Zzero$ resonance, averages are derived for di-fermion cross sections and forward-backward asymmetries, photon-pair, W-pair, Z-pair, single-W and single-Z cross sections, electroweak gauge boson couplings, W mass and width and W decay branching ratios. Also, an investigation of the interference of photon and Z-boson exchange is presented, and colour reconnection and Bose-Einstein correlation analyses in W-pair production are combined. The main changes with respect to the experimental results presented in summer 2002 are updates to the mass of the W boson, four-fermion cross sections and gauge couplings, all measured at LEP-2, and the LEP heavy-flavour results measured at the Z pole. The results are compared with precise electroweak measurements from other experiments, notably the recent final result on the electroweak mixing angle determined in neutrino-nucleon scattering by the NuTeV collaboration and the new result in atomic parity violation in Caesium. The parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of electroweak results.