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Published November 1, 2017 | Published
Journal Article Open

Measurement of the e^+e^− → π^+π^−π^0π^0 cross section using initial-state radiation at BABAR


The process e^+e^− → π^+π^−2π^0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3  fb^(-1) of data collected around a center-of-mass energy of √s = 10.58  GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel's contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (g^(π+π−2π^0)_μ−2)/2=(17.9 ± 0.1_(stat) ± 0.6_(syst))×10^(-10) in the energy range 0.85  GeV < E_(CM) < 1.8  GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z^0-pole is determined as Δα^(π+π−2π0)(M^2_Z) = (4.44 ± 0.02_(stat) ± 0.14_(syst))×10^(-4). Furthermore, intermediate resonances are studied and especially the cross section of the process e^+e^− → ωπ^0 → π^+π^−2π^0 is measured.

Additional Information

© 2017 American Physical Society. Received 5 September 2017; published 29 November 2017. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relies critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions thank SLAC for its support and the kind hospitality extended to them. This work is supported by the U.S. Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l'Energie Atomique and Institut National de Physique Nucléaire et de Physique des Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Economía y Competitividad (Spain), the Science and Technology Facilities Council (United Kingdom), and the Binational Science Foundation (U.S. and Israel). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation (USA). The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

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Published - PhysRevD.96.092009.pdf


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