Improved Determination of the Hadronic Contribution to the Muon (g-2) and to alpha(M_Z**2) Using new Data from Hadronic Tau Decays

TL;DR

This paper refines the calculation of the hadronic contributions to the muon g-2 and alpha(M_Z^2) by incorporating new tau decay data and extensive e+e- data, reducing uncertainties significantly.

Contribution

It introduces a new evaluation method combining tau decay data with e+e- data, improving the precision of hadronic contribution estimates to fundamental constants.

Findings

Reduced uncertainty in the pion form factor by more than a factor of two.

Provided updated values for hadronic vacuum polarization contributions to muon g-2.

Enhanced the accuracy of alpha(M_Z^2) calculations using combined data sets.

Abstract

We have reevaluated the hadronic contribution to the anomalous magnetic moment of the muon (g-2) and to the running of the QED fine structure constant alpha(s) at s=M_Z**2. We incorporated new data from hadronic tau decays, recently published by the ALEPH Collaboration. In addition, compared to previous analyses, we use more extensive e+e- annihilation data sets. The integration over the total hadronic cross section is performed using experimental data up to 40 GeV and results from perturbative QCD above 40 GeV. The improvement from tau data concerns mainly the pion form factor, where the uncertainty in the corresponding integral could be reduced by more than a factor of two. We obtain for the lowest order hadronic vacuum polarization graph a_mu(had) = (695.0 +/- 15.0) x 10^{-10} and delta(alpha(M_Z**2))(had) = (280.9 +/- 6.3) x 10^{-4} using e+e- data only. The corresponding results for combined e+e- and tau data are a_mu(had) = (701.1 +/- 9.4) x 10^{-10} and delta(alpha(M_Z**2))(had) = (281.7 +/- 6.2) x 10^{-4}, where the latter is calculated using the contribution from the five lightest quarks.