Volume 364 - European Physical Society Conference on High Energy Physics (EPS-HEP2019) - QCD and Hadronic Physics
A new evaluation of the hadronic vacuum polarisation contributions to the muon $\mathbf{g-2}$ and $\mathbf{\alpha(m^2_Z)}$
Z.P. Zhang
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Abstract
The hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the $Z$-boson mass are reevaluated. Newest $e^+e^- \to {\rm hadrons}$ cross-section data are included together with a phenomenological fit of the $\pi^+\pi^-$ 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 $(g-2)/2$, the lowest-order hadronic contribution obtained is $(693.9 \pm 4.0)\cdot10^{-10}$. The full Standard Model prediction differs by $3.3\sigma$ from the experimental value. The five-quark hadronic contribution to $\alpha(m^2_Z)$ is evaluated to be $(276.1\pm1.0)\cdot10^{-4}$.
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