Measurement of σ(e+e-→π+π-γ(γ)) and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section σ(e+e-→π+π-γ(γ)) at DAΦNE, the Frascati φ-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb-1. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<Mππ<0.975 GeV. For the latter we find Δππaμ=(387.2±0.5stat±2.4exp±2.3th)x10-10