Measurement of $σ(e^+e^-\to π^+ π^- γ)$ and extraction of $σ(e^+e^-\to π^+π^-)$ below 1 {\rm GeV} with the KLOE detector

Abstract

We have measured the cross section $σ(e^+e^-\to π^+π^- γ)$ at an energy $W=m_ϕ=1.02$ GeV with the KLOE detector at the electron-positron collider DA$Φ$NE. From the dependence of the cross section on the invariant mass of the two-pion system, we extract $σ(e^+e^-\to π^+π^-)$ for the mass range $0.35<s<0.95$ GeV$^2$. From this result, we calculate the pion form factor and the hadronic contribution to the muon anomaly, $a_μ$.