"Production of pion and muon pairs in e^± e^- colliding beams, going out of the limits of equivalent photon approximation"

Abstract
The reactions e^± e^- → e^± e^- π⁺ π^- (µ⁺ µ^-) are considered here in such a set-up, where only pions (muons) are recorded and k_<< total transverse momentum of the pair is not too small (roughly speaking m²_e ⊥ k²_⊥ << m²_π ; this domain gives the main contribution to the cross section). In the paper the differential cross sections have been obtained with accuracy of [MATH]. The amplitudes with the one scalar photon have to be taken into account in this approximation. Besides, the charge asymmetry appears here due to the interference of the two-photon and bremsstrahlung diagrams. It is shown what information on the amplitudes of the reaction and the pion electromagnetic form factor can be obtained from experiment in the given set-up.