https://doi.org/10.1140/epjc/s2003-01362-6
experimental physics
Updated estimate of the muon magnetic momentusing revised results from e + e -annihilation
1
Laboratoire de l’Accélérateur Linéaire, IN2P3-CNRS et Université de Paris-Sud, 91898 , Orsay, France
2
Budker Institute of Nuclear Physics, 630090, Novosibirsk, Russia
* e-mail: davier@lal.in2p3.fr
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
