Initial-state radiation measurement of the e^{+}e^{-}→π^{+}π^{-}π^{+}π^{-} cross section

We study the process e +e -→π +π -π +π -γ, with a photon emitted from the initial-state electron or positron, using 454.3fb -1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260000 signal events. We use these data to extract the nonradiative σ(e +e -→π +π -π +π -) cross section in the energy range from 0.6 to 4.5 GeV. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.