TL;DR
This paper presents an updated, precise measurement of the strong coupling constant alpha_s at the tau mass scale using spectral functions, comparing perturbative methods and estimating systematic uncertainties, resulting in a highly accurate alpha_s(M_Z).
Contribution
It provides a refined determination of alpha_s(m_tau) from tau decays, analyzing perturbative approaches and systematic effects, achieving one of the most precise alpha_s(M_Z) values from tau data.
Findings
Contour-improved perturbation theory shows better convergence than fixed-order.
Systematic effects from quark-hadron duality violations are within estimated errors.
The measured alpha_s(M_Z) aligns with values from Z decays, confirming consistency.
Abstract
An updated measurement of alpha_s(m_tau) from ALEPH tau hadronic spectral functions is presented. We report a study of the perturbative prediction(s) showing that the fixed-order perturbation theory manifests convergence or principle problems not presented in the contour-improved calculation. Potential systematic effects from quark-hadron duality violations are estimated to be within the quoted systematic errors. The fit result is alpha_s(m_tau) = 0.344 +- 0.005 +- 0.007, where the first error is experimental and the second theoretical. After evolution, the alpha_s(M_Z) determined from tau data is one of the most precise to date, in agreement with the corresponding NNNLO value derived from Z decays.
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Taxonomy
TopicsParticle physics theoretical and experimental studies · Quantum Chromodynamics and Particle Interactions · High-Energy Particle Collisions Research