Hadronic Z- and tau-Decays in Order alpha_s^4

Details Hadronic Z- and tau-Decays in Order alpha_s^4 Hadronic Z- and tau-Decays in Order alpha_s^4

2008-01-11

arxiv.org/abs/0801.1821v2

Phys.Rev.Lett.101:012002,2008

Physics

High Energy Physics

High Energy Physics - Phenomenology

few citations added, final published version

Scientific paper

10.1103/PhysRevLett.101.012002

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.

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