${\alpha }_s$ analyses from hadronic tau decays with OPAL and ALEPH data

Abstract

Recently, we extracted the strong coupling, ${\alpha }_s(m_{\tau }^2)$, from the revised ALEPH data for non-strange hadronic tau decays. Our analysis is based on a method previously used for the determination of the strong coupling from OPAL data. In our strategy, we employ different moments of the spectral functions both with and without pinching, including Duality Violations, in order to obtain fully self-consistent analyses that do not rely on untested assumptions (such as the smallness of higher dimension contributions in the OPE). Here we discuss the ${\alpha }_s$ values obtained from the ALEPH and the OPAL data, the robustness of the analysis, as well as non-perturbative contributions from DVs and the OPE. We show that, although the ${\alpha }_s$ determination is sound, non-perturbative effects limit the accuracy with which one can extract the strong coupling from tau decay data. Finally, we discuss the compatibility of the data sets and the possibility of a combined analysis.

arXiv commentInvited contribution to the workshop "Determination of the Fundamental Parameters in QCD" (MITP/Mainz, 7-11 March 2016). 14 pages 5 figures

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• The strong coupling from hadronic $\tau$ decays: a critical appraisal