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On the Behavior of the Effective QCD Coupling alpha_tau(s) at Low Scales

Stanley J. Brodsky·Sven Menke·Carlos Merino·Johan Rathsman
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Abstract

The hadronic decays of the tau lepton can be used to determine the effective charge alpha_tau(m^2_tau') for a hypothetical tau-lepton with mass in the range 0 < m_tau' < m_tau. This definition provides a fundamental definition of the QCD coupling at low mass scales. We study the behavior of alpha_tau at low mass scales directly from first principles and without any renormalization-scheme dependence by looking at the experimental data from the OPAL Collaboration. The results are consistent with the freezing of the physical coupling at mass scales s = m^2_tau' of order 1 GeV^2 with a magnitude alpha_tau ~ 0.9 +/- 0.1.

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Stanley J. Brodsky, Sven Menke, Carlos Merino, Johan Rathsman. 2003-01-23. On the Behavior of the Effective QCD Coupling alpha_tau(s) at Low Scales. https://doi.org/10.1103/physrevd.67.055008

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