Scanning of the e+e- → π+π- cross section below 1 GeV at DAΦNE by radiative events

The tagged photon events for the measurement of the e+e- → π+π- total cross section by the radiative return method at DAΦNE is discussed. The effects caused by the not exactly head-on collision of beams and by the QED radiative corrections are investigated. The essential part consists of the analysis of the event selection rules that ensure the rejection of the 3-pion hadronic state and take the main properties of the multiple purpose KLOE detector into account. The study of the non-head-on effect is performed in the Born approximation by integrating over the tagged photon angles, whereas the radiative corrections are calculated neglecting this effect. Together with the quasireal electron approach, this allows us to derive analytical formulas for the correction to the cross section of the initial-state radiative process. Some numerical calculations illustrate our analytical results