ELECTROWEAK EFFECTIVE CHARGES AND THEIR RELATION TO PHYSICAL CROSS-SECTIONS

In quantum electrodynamics with fermions f = e, mu...., knowledge of t he vacuum polarization spectral function determined from the tree-leve l e(+)e(-) --> f(+)f(-) cross sections, together with a single low-ene rgy measurement of the fine structure constant alpha, enables the cons truction of the one-loop effective charge alpha(eff)(q(2)) for all q(2 ). It is shown how an identical procedure can be followed in the elect roweak sector of the Standard Model to construct three gauge-, scale- and scheme-independent one-loop electroweak effective charges and an e ffective weak mixing angle from the tree-level e(+)e(-) --> W+W-, ZH a nd e(+)nu(e) --> W(+)Z, W(+)gamma, W+H differential cross sections, to gether with three low-energy measurements, which may be chosen to be a lpha and the masses of the W and Z bosons. It is found that the corres ponding proper self-energy-like functions thus constructed are identic al to those obtained in the pinch technique framework. In this way, it is shown how the concept of effective charges in the electroweak Stan dard Model is as well defined and unique as in quantum electrodynamics . (C) 1997 Elsevier Science B.V. PACS: 12.15.Lk; 11.55.Fv.