Measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ cross section in the energy range 0.62-3.50 GeV at Belle II

Abstract

We report a measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an $e^{+}{e}^{-}$ data sample corresponding to 191 ${\text{fb}}^{-1}$ of integrated luminosity, collected at a center-of-mass energy at or near the ${\rm Y}(4S)$ resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0\gamma$ events, which involve a ${\pi }^0\to \gamma \gamma$ decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the $\omega$ and $\varphi$ resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62-1.80 GeV energy range yield $a_{\mu }^{3\pi }=[48.91\pm 0.23(\mathrm{stat})\pm 1.07(\mathrm{syst})]\times 10^{-10}$ for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by $2.5$ standard deviations from the most precise current determination.

23 pages, 24 figures, submitted to PRD

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Cited by in corpus (2)

• Radiative corrections and Monte Carlo tools for low-energy hadronic cross sections in $e^{+}{e}^{-}$ collisions
• Ordinary and exotic mesons in the extended Linear Sigma Model