A New Precise Measurement of the e+e-→π+π-(γ) Cross Section with the Initial-State Radiation Method at BaBar
Abstract
We measure the e+e-→π+π-(γ) cross section from threshold to 1.4 GeV using 460 fb−1 of BaBar initial-state radiation data. The result is obtained from the π+π-/μ+μ- ratio, reducing systematic uncertainties that are in common. Unlike the previous 2009 BaBar analysis, the pion and muon contributions are separated statistically through their angular distributions. The compatibility with the previous BaBar result is quantified including statistical and systematic correlations. The new measurement is also compared with other two-pion results as a function of energy and in terms of its hadronic vacuum polarization (HVP) contribution to the muon magnetic anomaly. The leading-order HVP contribution of the two-pion channel in the energy range of 0.3−1.4 GeV is aμππ=525.9± 3.5stat±3.8syst and 517.8± 2.4stat±3.3syst in units of 10−10 for the new 2026 and combined 2009 and 2026 BaBar measurements, respectively.
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BibTeX
@misc{collaboration2026precise,
title = {{A New Precise Measurement of the $e^+e^-\toπ^+π^-(γ)$ Cross Section with the Initial-State Radiation Method at BaBar}},
author = {BaBar Collaboration},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.04596},
eprint = {2611.04596},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.04596},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A New Precise Measurement of the e^+e^-→π^+π^-(γ) Cross Section with the Initial-State Radiation Method at BaBar
AU - BaBar Collaboration
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.04596
UR - https://arxiv.org/abs/2611.04596
AB - We measure the e^+e^-→π^+π^-(γ) cross section from threshold to 1.4 GeV using 460 fb^−1 of BaBar initial-state radiation data. The result is obtained from the π^+π^-/μ^+μ^- ratio, reducing systematic uncertainties that are in common. Unlike the previous 2009 BaBar analysis, the pion and muon contributions are separated statistically through their angular distributions. The compatibility with the previous BaBar result is quantified including statistical and systematic correlations. The new measurement is also compared with other two-pion results as a function of energy and in terms of its hadronic vacuum polarization (HVP) contribution to the muon magnetic anomaly. The leading-order HVP contribution of the two-pion channel in the energy range of 0.3−1.4 GeV is a_μ^ππ=525.9± 3.5_stat±3.8_syst and 517.8± 2.4_stat±3.3_syst in units of 10^−10 for the new 2026 and combined 2009 and 2026 BaBar measurements, respectively.
ER -