INCORPORATION OF QCD EFFECTS IN BASIC CORRECTIONS OF THE ELECTROWEAK THEORY

We study the incorporation of QCD effects in the basic electroweak corrections DELTAr, DELTAr(W), and DELTAr. They include perturbative O(alphaalpha(s)) contributions and ttBAR threshold effects. The latter are studied in the resonance and Green-function approaches, in the framework of dispersion relations that automatically satisfy relevant Ward identities. Refinements in the treatment of the electroweak corrections, in both the modified minimal subtraction (MSBAR) and the on-shell schemes of renormalization, are introduced, including the decoupling of the top quark in certain amplitudes, its effect on e2(m(Z)) and sin2theta(W)(m(Z)), the incorporation of recent results on the leading irreducible O(alpha2) corrections, and simple expressions for the residual, i.e., ''nonelectromagnetic,'' parts of DELTAr, DELTAr(W), and DELTAr. The results are used to obtain accurate values for mw and sin2theta(W)(m(Z)), as functions of m(t) and m(H). The higher-order effects induce shifts in these parameters comparable to the expected experimental accuracy, and they increase the prediction for mt derived from current measurements. The MSBAR and the on-shell calculations of DELTAr, in a recently proposed formulation, are compared and found to be in excellent agreement over the wide ranges 60 GeV less-than-or-equal-to m(H) less-than-or-equal-to 1 TeV, m(Z) less-than-or-equal-to m(t) < 250 GeV.