Measurement of σ(ee→ππγ(γ)) and the dipion contribution to the muon anomaly with the KLOE detector

We have measured the cross section σ(ee→ππγ(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<M<0.975 GeV. For the latter we find Δa=(387.2±0.5±2.4±2.3)×10.