Improved Evaluation of the Hadronic Vacuum Polarization Contributions to Muon $g-2$ and $\bar\alpha_{\rm QED}(M_Z)$ Using High Order QCD Calculations

Abstract

We use recently evaluated radiative and nonperturbative corrections to production of heavy quarks by a vector current to give very precise theoretical calculations of the high energy ($t^{1/2}\geq \sqrt{2}$ GeV) imaginary part of the photon vacuum polarization function, ${\rm Im}\Pi(t)$. This allows us to improve the corresponding contributions to the muon (or any other lepton) $g-2$ anomaly and to the running QED constant on the $Z$, $\bar\alpha_{\rm QED}(M_Z)$. This decreases the error in the evaluations by a factor between two and six for the high energy contribution, and by some 50\% for the overall result. We find for the hadronic contributions $a_h=6993.4\pm110.0\times10^{-11}$ and $\Delta\alpha_h=272.59\pm4.09\times10^{-4}\,.$