Hadronic Z- and tau-Decays in Order alpha_s^4
Abstract
Using recently developed methods for the evaluation of five-loop amplitudes in perturbative QCD, corrections of order alpha_s^4 for the cross section of electron-positron annihilation into hadrons and for the decay rates of the Z-boson and the tau-lepton into hadrons are evaluated. The new terms lead to a significant stabilization of the perturbative series, to a reduction of the theory uncertainly in the strong coupling constant alpha_s, as extracted from these measurements, and to a small shift of the central value, moving two central values closer together. The agreement between two values of alpha_s measured at vastly different energies constitutes a striking test of asymptotic freedom. Combining the results from Z and tau decays we find alpha_s(M_Z)=0.1198 \pm 0.0015 as one of the most precise and presently only result for the strong coupling constant in order alpha_s^4.
Cite
@article{arxiv.0801.1821,
title = {Hadronic Z- and tau-Decays in Order alpha_s^4},
author = {P. A. Baikov and K. G. Chetyrkin and J. H. Kühn},
journal= {arXiv preprint arXiv:0801.1821},
year = {2008}
}
Comments
few citations added, final published version