Electroweak Theory and the 1996/97 Precision Electroweak Data

Abstract

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 < 430 GeV [680 GeV] at 95% C.L. based on the input of \swbar^2(\LEP+\SLD)_{`97} = 0.23152 +- 0.00023 [\swbar^2(\LEP)_{`97} = 0.23196 +- 0.00028]. The LEP2 data provide first direct experimental evidence for non-zero non-Abelian couplings among the electroweak vector bosons.