Measurement of the hadronic cross section at KLOE using the radiative return

Abstract

We report on the measurement of the hadronic cross section below 1GeV at the electron-positron-collider DAPHNE, using the multiple purpose detector KLOE. The radiative return, which is due to initial state radiation (e+ e- \to gamma + hadrons), allows us to obtain the cross section for variable center-of-mass-energies of the hadronic system from the 2m_pi threshold up to 1.02GeV. This measurement can be performed while DAPHNE is running with a fixed accelerator energy on the phi mass (1.02 GeV). For the exclusive process e+ e- \to pi+ pi- gamma, the status of the analysis and first preliminary results of the invariant mass spectrum of the two-pion-state are presented.