Top quark contribution to hadronic decays of the Z-boson at α 2 s in QCD

We evaluate the effect of a virtual top quark on the coefficient of α2s in the decay rates Γ(Z → hadrons) and Γ(Z → bb). We treat the dependence on the top quark mass exactly instead of using a large mass expansion. The present work completes the evaluation of the α2s contributions to these quantities. The calculation uses both the MS and Collins-Wilczek… CONTINUE READING