Measurement of initial-state–final-state radiation interference in the processes $e^+e^- → μ^+μ^-γ$ and $e^+e^- → π^+π^-γ$

J.P. Lees, G. Raven

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Abstract

Charge asymmetry in the processes e+e-→μ+μ-γ and e+e-→π+π-γ is measured using 232 fb-1 of data collected with the BABAR detector at e+e- center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial- and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+e-→μ+μ-γ, and from theoretical models for e+e-→π+π-γ. A clear interference pattern is observed in e+e-→π+π-γ, particularly in the vicinity of the f2(1270) resonance. The inferred rate of lowest-order FSR production is consistent with the QED expectation for e+e-→μ+μ-γ, and is negligibly small for e+e-→π+π-γ.
Original languageEnglish
Pages (from-to)072015
JournalPhysical Review D
Volume92
Issue number7
DOIs
Publication statusPublished - 2015

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Lees:2015qna

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