Measurement of the e+e−→ hadrons cross-section at low energy with ISR events at BABAR

The precise measurement of the cross section e+e−→π+π−(γ) from threshold to an energy of 3 GeV, using events with Initial State Radiation (ISR) collected with the BABAR detector, is presented. The ISR luminosity is determined from a study of the leptonic process e+e−→μ+μ−γ(γ), and the method is tested by the comparison with the next-to-leading order (NLO) QED prediction. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the BABAR ππ cross section measured from threshold to 1.8 GeV is (514.1±2.2(stat)±3.1(syst))×10−10. Other results on ISR multihadronic cross sections from BABAR are presented.