Determination of $σ(e^+e^-\to π^+ π^-)$ from radiative processes at DA$Φ$NE

Abstract

We have measured the cross section $σ(e^+e^-\toπ^+π^-γ)$ with the KLOE detector at DA$Φ$NE, at an energy $W=M_ϕ=1.02$ GeV. From the dependence of the cross section on $m(π^+π^-)=\sqrt{W^2-2WE_γ}$, where $E_γ$ is the energy of the photon radiated from the initial state, we extract $σ(e^+e^-\toπ^+π^-)$ for the mass range $0.35<m^2(π^+π^-)<0.95$ GeV$^2$. From our result we extract the pion form factor and the hadronic contribution to the muon anomaly, $a_μ$.