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−)B(ω→π+π−π0)=(0.5698±0.0031±0.0082) keV, Γ(ϕ→e+e−)B(ϕ→π+π−π0)=(0.1841±0.0021±0.0080) keV, and 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−)B(J/ψ→3π)=(0.1248±0.0019±0.0026) keV.21 MoreReceived 4 October 2021Accepted 12 November 2021DOI:https://doi.org/10.1103/PhysRevD.104.112003Published 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.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle interactionsPhysical SystemsLight mesonsQuarkoniaTechniquesLepton collidersParticle productionParticles & Fields
Highlights
The process eþe− → πþπ−π01 has the second largest hadronic cross section after eþe− → πþπ− in the energy region below 1 GeV and is very important for the Standard Model calculation of the anomalous magnetic moment of the muon aμ ≡ ðg − 2Þμ=2
We study the process eþe− → πþπ−π0γ, where the photon emission is caused by initial-state radiation
Signal and background initial-state radiation (ISR) processes are simulated by a Monte Carlo (MC) event generator based on the approach suggested in Ref. [14]
Summary
The process eþe− → πþπ−π01 has the second largest hadronic cross section after eþe− → πþπ− in the energy region below 1 GeV and is very important for the Standard Model calculation of the anomalous magnetic moment of the muon aμ ≡ ðg − 2Þμ=2. The most precise measurements of the eþe− → πþπ−π0 cross section in the energy region of the ω and φ resonances were performed by the SND and CMD-2 Collaborations at the VEPP-2M eþe− collider [2,3,4,5]. The φ meson resonance the latest measurements come from the BABAR experiment [6], which used the initial-state radiation (ISR). There is a preliminary result from the BESIII experiment [8], which measured the eþe− → πþπ−π0 cross section in the energy range between 0.7 and. We require that the ISR photon be detected The goal of this analysis is to improve the accuracy of the eþe− → πþπ−π0 cross section measurement and the contribution of this process to aμ
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