alpha_s from tau decays: Contour-improved versus fixed-order summation in a new QCD perturbation expansion

0345228 - FZÚ 2011 RIV DE eng J - Journal Article
Caprini, I. - Fischer, Jan
alpha_s from tau decays: Contour-improved versus fixed-order summation in a new QCD perturbation expansion.
European Physical Journal C. Roč. 64, č. 1 (2009), s. 35-45. ISSN 1434-6044. E-ISSN 1434-6052
R&D Projects: GA MŠMT LA08015
Institutional research plan: CEZ:AV0Z10100502
Keywords : strong coupling * tau decay * QCD * perturbation * expansion * conformal mapping
Subject RIV: BF - Elementary Particles and High Energy Physics
Impact factor: 2.746, year: 2009
http://www.springerlink.com/content/c1p8377l50770l34/fulltext.pdf

We consider the determination of $/alpha_s$ from τ hadronic decays, by investigating the CIPT and the FOPT renormalization group summations in the frame of a new perturbation expansion of QCD, which incorporates in a systematic way the available information about the divergent character of the series. The new expansion functions are defined by the analytic continuation in the Borel complex plane, achieved through an optimal conformal mapping. Using a model discussed by Beneke and Jamin, we show that the new CIPT approaches the true results with great precision when the perturbative order is increased, while the new FOPT gives a less accurate description in the regions where the imaginary logarithms present in the expansion of the running coupling are large. From the new CIPT we predict $/alpha_s(m_/tau^2)= 0.320 ^{+0.011}_{-0.009}$.
Permanent Link: http://hdl.handle.net/11104/0186544