Measurement of $\sigma(e^+e^- \to \pi^+\pi^-)$ at DA$\Phi$NE with the radiative return

Abstract

The measurement of hadronic cross sections at low centre-of-mass energies is currently attracting much interest because of the r\^o{}le these measurements play in the theoretical evaluation of the anomalous magnetic moment of the muon. The KLOE experiment at the DA$\Phi$NE $\phi$-factory in Frascati aims to determine the cross section of the dominant contribution $e^{+}e^{-} \to \pi^{+}\pi^{-}$ at energies below 1 GeV exploiting the radiative return from the $\phi$ to the $\rho$ and $\omega$ mesons. This method has systematic errors completely different from previous measurements and allows a cross check of existing data in this energy region. The method and results on both the differential cross section for $e^{+}e^{-} \to \pi^{+}\pi^{-}\gamma$ and the total cross section for $e^{+}e^{-} \to \pi^{+}\pi^{-}$ are presented.