arXiv:hep-ph/0212078·v3·High Energy Physics — Phenomenology
On the Behavior of the Effective QCD Coupling alpha_tau(s) at Low Scales
Stanley J. Brodsky (1)🇺🇸 · Sven Menke (1 and 2)🇺🇸 · Carlos Merino (1 and 3)🇺🇸 · Johan Rathsman (4) ((1) SLAC, Stanford University, (2) MPI fuer Physik, Muenchen, (3) Department of Particle Physics, University of Santiago de Compostela, (4) High Energy Physics, Uppsala University)🇸🇪
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.
Comments: 15 pages, 4 figures, submitted to Physical Review D, added references, some text added, no results nor figures changed