On the radiative corrections to the electroweak parameters and precision tests of the electroweak theory

The radiative corrections to the electroweak parameters are reconsidered with an emphasis on analysing prospects for future tests of the as yet untested parts of the electroweak theory, in particular the 'new physics' of vector-boson self-interactions and the Higgs scalar. The vacuum polarization due to the light fermions is treated in the leading-long approximation, while the top-quark is taken into account exactly. A detailed analysis of the errors involved in our approximations and a comparison with the results of complete on-loop calculations shows that vacuum polarization due to bosons is negligible, if mH = 100 GeV, while it may become visible in precision tests in e+e- annihilation, if mH ≅ 1 TeV. We also give detailed results (as a function of the top-quark mass) on the radiatively corrected parameters used in model-independent fits to neutrino-scattering and in the interpretation of atomic-parity violation experiments. Technically, we diagonalize the γ-Z propagator for any q2, and we show, when treating the top-quark vacuum polarization exactly, that the intuitively appealing notion of running coupling constants can be used beyond the leading-log approximation. (orig.)