A new evaluation of the hadronic vacuum polarisation contributions to the muon anomalous magnetic moment and to α(mZ2)

Abstract

We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass. We include newest $e^{+}{e}^{-}\to \mathrm{hadrons}$ cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant ${\pi }^{+}{\pi }^{-}$ channel. For the muon $(g-2)/2$, we find for the lowest-order hadronic contribution $(694.0\pm 4.0)·{10}^{-10}$. The full Standard Model prediction differs by $3.3\sigma$ from the experimental value. The five-quark hadronic contribution to $\alpha (m_Z^2)$ is evaluated to be $(276.0\pm 1.0)·{10}^{-4}$.