Measurement of the e+e− → π+π−π+π−, K+K−π+π−, K+K−K+K− Cross Sections Using Initial State Radiation at BABAR

First results of a study of the e+e− → π+π−π+π−γ process with hard photon emitted from initial state are presented. About 60000 fully reconstructed events have been selected based on 89.3 fb−1 of BABAR data. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and so BABAR ISR data can be compared to the relevant direct e+e− measurements. From obtained 4π mass spectrum we evaluate e+e− → π+π−π+π− cross section for the range of c.m.s. energy from 0.6 to 4.5 GeV. The systematic error of the cross section measurement is 5% and comparable with the best e+e− data. The cross sections for identified 2K2π and 4K final states also have been presented.