Updated estimate of the muon magnetic momentusing revised results from e + e -annihilation
Laboratoire de l’Accélérateur Linéaire, IN2P3-CNRS et Université de Paris-Sud, 91898 , Orsay, France
2 Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia
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A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e + e -annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e + e -and spectral functions in the channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and , so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are
where the errors have been separated according to their sources: experimental, missing radiative corrections in e + e -data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read
where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be (1.9 ) and (0.7 ) for the e + e -- and -based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.
© Springer-Verlag, 2003