The muon $g-2$: a brief overview of hadronic cross section data

Abstract

The hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu }^{\mathrm{had},\mathrm{VP}}$ are evaluated dispersively via a combination of experimentally measured $e^{+}{e}^{-}\to \mathrm{hadrons}$ cross section data. Many experiments have dedicated programmes to precisely measure these final states, meaning that a vast amount of data is now available and that, in some cases, overall precision has reached the sub-percent level. However, data tensions are evident between measurements of the same hadronic channels from different experiments, which reduces the overall quality of the data combinations used to determine $a_{\mu }^{\mathrm{had},\mathrm{VP}}$. The inclusion of these data in the KNT18 analysis results in $a_{\mu }^{\mathrm{had},\mathrm{LO}\mathrm{VP}}=(693.26\pm 2.46)\times 10^{-10}$ and $a_{\mu }^{\mathrm{had},\mathrm{NLO}\mathrm{VP}}=(-9.82\pm 0.04)\times 10^{-10}$. The corresponding new estimate for the Standard Model prediction is found to be $a_{\mu }^{\mathrm{SM}}=(11659182.04\pm 3.56)\times 10^{-10}$, which is $3.7\sigma$ below the current experimental measurement.

Comments: The 9th International Workshop on Chiral Dynamics. arXiv admin note: text overlap with arXiv:1802.06229