# Differences

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+ | ====== TTP08-01 Hadronic Z- and tau-Decays in Order alpha_s^4 ====== | ||

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+ | <hidden TTP08-01 Hadronic Z- and tau-Decays in Order alpha_s^4 > 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 NNNLO result for the strong coupling constant. | ||

+ | </hidden> | ||

+ | |**P.A. Baikov, K.G. Chetyrkin and J.H.K\"uhn** | | ||

+ | |** Phys. Rev. Lett. 101 012002 2008 ** | | ||

+ | | {{preprints:2008:ttp08-01.pdf|PDF}} {{preprints:2008:ttp08-01.ps|PostScript}} [[http://arxiv.org/abs/0801.1821|arXiv]] | | ||

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