A new RG-summation method for extraction of αs(Mτ) from hadronic tau decays

por Gauhar Abbas (Centre for High Energy Physics, Bangalore (India))

jueves 3 may. 2012 12:00 → 13:00 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

We provide a new determination of strong coupling αs(Mτ) using an improved fixed-order perturbation theory based on the explicit summation of all renormalization-group accessible logarithms, proposed some time ago in the literature. In this approach, the powers of the coupling in the expansion of the QCD Adler function are multiplied by a set of functions Dn , which depend themselves on the coupling and can be written in a closed form by iteratively solving a sequence of differential equations. We find that the new expansion has an improved behaviour in the complex energy plane compared to that of the standard fixed-order perturbation theory (FOPT), and is similar but not identical to the contour-improved perturbation theory (CIPT). With five terms in the perturbative expansion we obtain in the MS scheme αs(Mτ) = 0.338 ± 0.010.