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The process e+e→ π+ππ0γ is studied at a center-of-mass energy near the ϒ(4S) resonance using a data sample of 469 fb−1 collected with the BABAR detector at the PEP-II collider. We have performed a precise measurement of the e+eπ+ππ0 cross section in the center-of-mass energy range from 0.62 to 3.5 GeV. In the energy regions of theω and ϕ resonances, the cross section is measured with a systematic uncertainty of 1.3%. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured e+eπ+ππ0 cross section from threshold to 2.0 GeV is (45.86 plusmn; 0.14 plusmn; 0.58) × 10−10. From the fit to the measured 3π mass spectrum we have determined the resonance parameters Γ(ω → e+e−)B(ω → π+π-π0)= (0.5698 plusmn; 0.0031 plusmn; 0.0082) keV, Γ(ϕ → e+e) B(ϕ → π+π+π0) = (0.1841 plusmn; 0.0021 plusmn; 0.0080) keV, and B(ρ → 3π)=(0.88 plusmn;0.23 plusmn; 0.30) × 10−4. The significance of the ρ → 3π signal is greater than 6σ. For the J=ψ resonance we have measured the product Γ(J /ψ →e+e−)B(J/ψ→3π)=(0.1248±0.0019±0.0026)  keV.

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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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Lees, J. P., Poireau, V., Tisserand, V., Grauges, E., Palano, A., Eigen, G., Brown, D. N., Kolomensky, Yu. G., Fritsch, M., Koch, H., Schroeder, T., Cheaib, R., Hearty, C., Mattison, T. S., McKenna, J. A., So, R. Y., Blinov, V. E., Buzykaev, A. R., Druzhinin, V. P., … Wu, S. L. (2021a). Study of the process . Physical Review D, 104(11).

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