Precision electroweak tests of the Standard Model

The present status of precision electroweak data is reviewed. These data include measurements of e⁺e^-→f\barf, taken at the Z resonance at LEP, which are used to determine the mass and width of the Z-boson. In addition, measurements have also been made of the forward-backward asymmetries for leptons and heavy-quarks, and also the final state polarization of the τ-lepton. At SLAC, where the electron beam was polarized, measurements were made of the left-right polarized asymmetry, A_LR, and the left-right forward-backward asymmetries for b- and c-quarks.

The mass, m_W, and width, Γ_W, of the W-boson have been measured at the Tevatron and at LEP, and the mass of the top-quark, m_t, has been measured at the Tevatron. These data, plus other electroweak data, are used in global electroweak fits in which various Standard Model (SM) parameters are determined. A comparison is made between the results of the direct measurements of m_W and m_t with the indirect results coming from electroweak radiative corrections. Using all precision electroweak data, fits are also made to determine limits on the mass of the Higgs boson, m_H. The influence on these limits of specific measurements, particularly those which are somewhat inconsistent with the SM, is explored. The data are also analysed in terms of the quasi-model-independent variables.

Finally, the impact on the electroweak fits of the improvements in the determination of the W-boson and top-quark masses, expected from the Tevatron Run 2, is examined.