Study of the process e⁺e^-→ π⁺π^-π⁰ using initial state radiation with BABAR

2021/10/01 by The BABAR Collaboration
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2110.00520

Abstract

The process e⁺e^-→ π⁺π^-π⁰γ 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⁺e^-→ π⁺π^-π⁰ cross section in the center-of-mass energy range from 0.62 to 3.5 GeV. In the energy regions of the ω 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⁺e^-→ π⁺π^-π⁰ cross section from threshold to 2.0 GeV is (45.86 ± 0.14 ± 0.58)× 10^-10. From the fit to the measured 3π mass spectrum we have determined the resonance parameters Γ(ω→ e⁺e^-)\cal B(ω→ π⁺π^-π⁰)=(0.5698±0.0031±0.0082) keV, Γ(ϕ→ e⁺e^-)\cal B(ϕ→ π⁺π^-π⁰)=(0.1841±0.0021±0.0080) keV, and \cal B(ρ→ 3π)=(0.88± 0.23± 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^-)\cal B(J/ψ→ 3π)=(0.1248±0.0019±0.0026) keV.

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