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.
@article{arxiv.0809.2823,
title = {Precise alpha_s from Tau Decays},
author = {Bogdan Malaescu},
journal= {arXiv preprint arXiv:0809.2823},
year = {2010}
}
Comments
4 pages, 2 figures. To appear in the proceedings of QCD08, Montpellier, France, 7-12th July 2008