1061 articles – 5064 Notices  [english version]
 HAL : in2p3-00155193, version 1
 arXiv : hep-ph/0701163
 Tau06 International Workshop, Pisa : Italie (2006)
 The hadronic contribution to (g-2) of the muon
 (2007)
 The evaluation of the hadronic contribution to the muon magnetic anomaly $a_\mu$ is revisited, taking advantage of new experimental data on $e^+e^-$ annihilation into hadrons: SND and CMD-2 for the $\pi^+\pi^-$ channel, and \babar for multihadron final states. Discrepancies are observed between KLOE and CMD-2/SND data, preventing one from averaging all the $e^+e^-$ results. The long-standing disagreement between spectral functions obtained from $\tau$ decays and $e^+e^-$ annihilation is still present, and not accounted by isospin-breaking corrections, for which new estimates have been presented. The updated Standard Model value for $a_\mu$ based on $e^+e^-$ annihilation data is now reaching a precision better than experiment, and it disagrees with the direct measurement from BNL at the 3.3$\sigma$ level, while the $\tau$-based estimate is in much better agreement. The $\tau$/$e^+e^-$ discrepancy, best revealed when comparing the measured branching fraction for $\tau^- \to \pi^- \pi^0 \nu_\tau$ to its prediction from the isospin-breaking-corrected $e^+e^-$ spectral function, remains a serious problem to be understood.
 Thème(s) : Physique/Physique des Hautes Energies - Phénoménologie
 Lien vers le texte intégral : http://fr.arXiv.org/abs/hep-ph/0701163
 in2p3-00155193, version 1 http://hal.in2p3.fr/in2p3-00155193 oai:hal.in2p3.fr:in2p3-00155193 Contributeur : Françoise Marechal <> Soumis le : Vendredi 15 Juin 2007, 17:08:57 Dernière modification le : Mercredi 19 Mars 2008, 14:55:21