Precise measurement of the e+ e- → π+ π- (γ) cross section with the initial state radiation method at BABAR

We present a precise BABAR measurement on the cross section of the process e+ e- → π+ π- (γ) from threshold to an energy of 3 GeV with the initial state radiation(ISR) technique,using 232 fb-1 of data collected with the BABAR detector at e+ e-center-of-mass energies near 10.58 GeV.The ISR luminosity is determined from a study of the leptonic process e+ e- → μ+ μ- γ (γ). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the π π cross section measured from threshold to 1.8 GeV is(514.1 ± 2.2(stat) ± 3.1(syst)) x 10-10. (author)