# Evaluation of alpha(m**2(z) and (g-2)(mu).

Abstract : his talk summarizes the recent developments in the evaluation of the leading order hadronic contributions to the running of the QED f\/ine structure constant \aqed, at $s=M_{\rm Z}^2$, and to the anomalous magnetic moment of the muon $(g-2)_\mu$. The accuracy of the theoretical prediction of these observables is limited by the uncertainties on the hadronic contributions. Signif\/icant improvement has been achieved in a series of new analyses which is presented historically in three steps: (I), use of $\tau$ spectral functions in addition to \eee\ cross sections, (II), extended use of perturbative QCD and (III), application of QCD sum rule techniques. The most precise values obtained are: \daqedhZ\,$=(276.3\pm1.6)\times10^{-4}$, yielding $\alpha^{-1}(M_{\rm Z}^2)=128.933\pm0.021$, and $a_\mu^{\rm had}=(692.4\pm6.2)\times 10^{-10}$ with which one f\/inds for the complete Standard Model prediction $a_\mu^{\rm SM}=(11\,659\,159.6\pm6.7)\times10^{-10}$. For the electron $(g-2)_e$, the hadronic contribution is $a_e^{\rm had}=(187.5\pm1.8)\times 10^{-14}$.
Document type :
Conference papers

http://hal.in2p3.fr/in2p3-00007502
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Submitted on : Monday, February 19, 2001 - 3:04:28 PM
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### Citation

M. Davier. Evaluation of alpha(m**2(z) and (g-2)(mu).. International Workshop on tau Physics 5, Sep 1998, Santander, Spain. pp.327-338. ⟨in2p3-00007502⟩

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