EPJ Web Conf.
Volume 137, 2017XIIth Quark Confinement and the Hadron Spectrum
|Number of page(s)||12|
|Published online||22 March 2017|
Precision physics with QCD
Departament de Física Teòrica, IFIC, Universitat de València – CSIC Edifici d’Instituts de Paterna, Apt. Correus 22085, E-46071, València, Spain
a e-mail: Antonio.Pich@ific.uv.es
Published online: 22 March 2017
The four-loop determination of the strong coupling from fully inclusive observables is reviewed. Special attention is given to the low-energy measurement extracted from the hadronic τ decay width. A recent exhaustive analysis of the ALEPH data, exploring several complementary methodologies with very different sensitivities to inverse power corrections and duality violations, confirms the strong suppression of non-perturbative contributions to Rτ. It gives the value αs(mτ2) = 0.328, which implies αs(MZ2) = 0.1197 ± 0.0015. The excellent agreement with the direct measurement at the Z peak, αs(MZ2) = 0.1196 ± 0.0030, provides a beautiful test of asymptotic freedom. Together with the most recent lattice average from FLAG and the NNLO determinations from e+e−, PDFs and collider data quoted by the PDG, these two inclusive determinations imply a world average value αs(MZ2) = 0.1180 ± 0.0010.
© The Authors, published by EDP Sciences, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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