1201.5804 (P. A. Baikov et al.)

Complete QCD Corrections to Hadronic $Z$--Decays in Order $α_s^4$    [PDF]

P. A. Baikov, K. G. Chetyrkin, J. H. Kühn, J. Rittinger

Corrections of order $\alpha_s^4$ for the axial singlet contributions for the
decay rates of the $Z$-boson into hadrons are evaluated in the limit of the
heavy top quark mass. Combined with recently finished ${\cal O}(\alpha_s^4)$
calculations of the non-signlet corrections, the new results directly lead us
to the first {\em complete} ${\cal O}(\alpha_s^4)$ prediction for the total
hadronic decay rate of the Z-boson.
The new ${\cal O}(\alpha_s^4)$ 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 $\alpha_s$, as extracted from these
measurements, and to a small shift of the central value.

View original: http://arxiv.org/abs/1201.5804