We report a measurement of the e+e− → π+π−π0 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 fb^−1 of integrated luminosity, collected at a center-of-mass energy at or near the ϒ(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− → π+π−π0γ events, which involve a π0 → γγ 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 ω and ϕ 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^{3π}_μ = [48.91 ± 0.23(stat) ± 1.07(syst)] × 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.
Measurement of the e+e− → π+π−π0 cross section in the energy range 0.62–3.50 GeV at Belle II
Bianchi, F.;Destefanis, M.;Maggiora, M.;Mussa, R.;Pinna Angioni, G.;Spataro, S.;Tamponi, U.;
2024-01-01
Abstract
We report a measurement of the e+e− → π+π−π0 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 fb^−1 of integrated luminosity, collected at a center-of-mass energy at or near the ϒ(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− → π+π−π0γ events, which involve a π0 → γγ 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 ω and ϕ 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^{3π}_μ = [48.91 ± 0.23(stat) ± 1.07(syst)] × 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.| File | Dimensione | Formato | |
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PhysRevD.110.112005.pdf
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