Measurement of the e+eπ+ππ0 cross section in the energy range 0.62-3.50 GeV at Belle II

Sumitted to PubDB: 2024-04-09

Category: Physics / performance paper, Visibility: Public

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Authors
Non-Belle II authors Belle II Collaboration
Date April 7, 2024
Belle II Number BELLE2-PUB-PH-2024-002
Abstract We report a measurement of the e+eπ+ππ0 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 fb1 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+eπ+ππ0γ events, which involve a π0γγ 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 aμ3π=[48.91±0.23 (stat)±1.07 (syst)]×1010 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.

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