QED corrections in the radiative return method during measurement of the e + e −→π+π− cross-section below 1 GeV

We discuss radiative corrections during the measurement of the e + e − →π + π − cross-section by the radiative return method without photon tagging. The radiative corrections to the initial-state radiation process are computed for DAΆNE conditions using the quasireal electron approximation for both the cross-section and the underlying kinematics. The efficiency of experimental rules for event selection by the restrictions on the lost invariant mass and so-called “track mass” is estimated. Some numerical calculations illustrate our analytical results.