ON THE ELECTROWEAK AND GLUONIC CORRECTIONS TO THE HADRONIC WIDTH OF THE Z-BOSON

The electroweak corrections to the Z-boson hadronic width are presented in a simple analytical form for the width itself, Gamma(h), for its ratio to the leptonic width, R(l) = Gamma(h)/Gamma(l), for the Gamma(b)/Gamma(h) ratio, and for the total width Gamma(Z). The rational parametrization, advocated in our recent papers on leptonic decays, simplifies the analysis of the hadronic decays too. There are two main results of this analysis: (1) All electroweak precision measurements agree within 1 sigma with the electroweak Born approximation if the gluon coupling constant ($) over bar alpha(s) = 0.12. Thus the electroweak radiative corrections have not been observed experimentally. The unexpected smallness of electroweak radiative corrections is caused by the mutual cancellation of the large positive contribution of a heavy top quark and the large negative contribution of all other virtual particles. (2) With electroweak radiative corrections being taken into account, the value of ($) over bar alpha(s) extracted from the experimental value of Gamma(Z) differs by greater than or equal to 3 sigma from that obtained from R(l), if m(t) greater than or equal to 200 GeV; they agree within 1 sigma if m(t) less than or equal to 150 GeV. Thus a low upper limit on mi can be obtained from hadronic decays of the Z-boson alone, even without data on its leptonic decays.