PUB - Publikationen an der Universität Bielefeld

We review the empirical evidence for the validity of the Standard Electroweak Theory in Nature. The experimental data are interpreted in terms of an effective Lagrangian for Z physics, allowing for potential sources of SU(2) violation and containing the predictions of the Standard Electroweak Theory as a special case. Particular emphasis is put on discriminating loop corrections due to fermion-loop vector-boson propagator corrections on the one hand, from corrections depending on the non-Abelian structure and the Higgs sector on the other hand. Results from recently obtained fits of the Higgs-boson mass are reported, yielding M-H less than or similar to 430 GeV [680 GeV] at 95% C.L. based on the input of (s) over bar(w)(2)(LEP + SLD)('97) = 0.23152 +/- 0.00023 [(s) over bar(w)(2)(LEP)('97) = 0.23196 +/- 0.00028]. The LEP2 data provide first direct experimental evidence for Iron-zero non-Abelian couplings among the electroweak vector bosons.