Paper
Complete QCD Corrections to Hadronic $Z$--Decays in Order $α_s^4$
Authors
P. A. Baikov, K. G. Chetyrkin, J. H. Kühn, J. Rittinger
Abstract
Corrections of order for the axial singlet contributions for the decay rates of the -boson into hadrons are evaluated in the limit of the heavy top quark mass. Combined with recently finished calculations of the non-signlet corrections, the new results directly lead us to the first {\em complete} prediction for the total hadronic decay rate of the Z-boson.
The new term in Z-decay rate lead to a significant stabilization of the perturbative series, to a reduction of the theory uncertainty in the strong coupling constant , as extracted from these measurements, and to a small shift of the central value.