Precise alpha_s from tau decay

International audienceAn updated measurement of α_s(m^2_τ) from ALEPH τ 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 α_s(m^2_τ) = 0.344±0.005±0.007, where the first error is experimental and the second theoretical. After evolution, the α_s(m^2_z) determined from τ data is one of the most precise to date, in agreement with the corresponding N^3LO value derived from Z decays