Precision measurement of σ(e+e−→π+π−γ)/σ(e+e−→μ+μ−γ) and determination of the π+π− contribution to the muon anomaly with the KLOE detector

We have measured the ratio σ(e+e−→π+π−γ)/σ(e+e−→μ+μ−γ), with the KLOE detector at DAΦNE for a total integrated luminosity of ∼240 pb−1. From this ratio we obtain the cross section σ(e+e−→π+π−). From the cross section we determine the pion form factor |Fπ|2 and the two-pion contribution to the muon anomaly aμ for 0.592