994 articles – 4726 Notices  [english version]
 HAL : in2p3-00155201, version 1
 arXiv : hep-ph/0701170
 9th International Workshop on Tau Lepton Physics (Tau06), Pisa : Italy (2006)
 ALEPH Tau Spectral Functions and QCD
 M. Davier1, A. Hoecker2, Z. Zhang1
 (2007)
 Hadronic $\tau$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $\tau$ decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, quark and gluon condensates. Using the ALEPH spectral functions and branching ratios, complemented by some other available measurements, and a revisited analysis of the theoretical framework, the value $\asm = 0.345 \pm 0.004_{\rm exp} \pm 0.009_{\rm th}$ is obtained. Taken together with the determination of \asZ from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of $\alpha_s^{-1}(s)$ is found to agree with QCD at a precision of 4%. The value of \asZ obtained from $\tau$ decays is $\asZ = 0.1215 \pm 0.0004_{\rm exp} \pm 0.0010_{\rm th} \pm 0.0005_{\rm evol}= 0.1215 \pm 0.0012$.
 Thème(s) : Physique/Physique des Hautes Energies - Phénoménologie
 Lien vers le texte intégral : http://fr.arXiv.org/abs/hep-ph/0701170
 in2p3-00155201, version 1 http://hal.in2p3.fr/in2p3-00155201 oai:hal.in2p3.fr:in2p3-00155201 Contributeur : Françoise Marechal <> Soumis le : Vendredi 15 Juin 2007, 17:24:34 Dernière modification le : Mercredi 19 Mars 2008, 14:50:39