On the electroweak and gluonic corrections to the hadronic width of the Z boson |
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Authors: | V A Novikov L B Okun M I Vysotsky |
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Institution: | a ITEP, Moscow 117259, Russia b Theoretical Physics Division, CERN, CH-1211, Geneva 23, Switzerland |
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Abstract: | The electroweak corrections to the Z-boson hadronic width are presented in a simple analytical form for the width itself, Λh, for its ratio to the leptonic width, Rl = Λh/Λl, for the Λb/Λh ratio, and for the total width ΛZ. 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 σ with the electroweak Born approximation if the gluon coupling constant
. 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
extracted from the experimental value of ΛZ differs by 3σ from that obtained from Rl, if mt 200 GeV; they agree within 1σ if mt 150 GeV. Thus a low upper limit on mt can be obtained from hadronic decays of the Z-boson alone, even without data on its leptonic decays. |
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