(g − 2)μ and α(M2Z) re-evaluated using new precise data

Abstract

We update our standard model predictions for g − 2 of the muon and for the hadronic contributions to the running of the QED coupling, Δα(5)had(M2Z). Particular emphasis is put on recent changes in the hadronic contributions from new data in the 2π channel and from the energy region just below 2 GeV. In particular, for the e+e− → π+π− contribution we include the recent ‘radiative return’ data from KLOE and BaBar. We also include the recent BaBar data on other exclusive channels. We make a detailed study of the effect of replacing the measurements of the inclusive cross section, σ(e+e− → hadrons), by the sum of the exclusive channels in the energy interval GeV, which includes a QCD sum-rule analysis of this energy region. Our favoured prediction for the muon anomalous magnetic moment is (g − 2)/2 = (11 659 182.8 ± 4.9) × 10−10 which is 3.3 σ below the present world-average measurement. We compare our g − 2 value with other recent calculations. Our prediction for the QED coupling, obtained via Δα(5)had(MZ2) = (276.26 ± 1.38) × 10−4 , is α(M2Z)−1 = 128.944 ± 0.019.