Reevaluation of the hadronic contribution to the muon g − 2 and to α ( M 2 Z )

We reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass. We include new π+π− cross-section data from KLOE, all available multi-hadron data from BABAR, a reestimation of missing low-energy contributions using results on cross sections and process dynamics from BABAR, a reevaluation of all experimental contributions using the software package HVPTools together with a reanalysis of inter-experiment and inter-channel correlations, and a reevaluation of the continuum contributions from perturbative QCD at four loops. These improvements lead to a decrease in the hadronic contributions with respect to earlier evaluations. For the muon g − 2 we find lowest-order hadronic contributions of (692.3±4.2) ·10−10 and (701.5±4.7) ·10−10 for the e+e−based and τ -based analyses, respectively, and full Standard Model predictions that differ by 3.6σ and 2.4σ from the experimental value. For the e+e−-based five-quark hadronic contribution to α(M2 Z) we find Δα (5) had(M 2 Z) = (274.9±1.0) · 10−4. The reduced electromagnetic coupling strength at MZ leads to an increase by 12 GeV in the central value of the Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.