Near threshold radiative 3π production in e+e- annihilation

The π+π-π0γ final state in electron-positron annihilation at the center-of-mass system energies not far from the threshold is considered. Both initial and final state radiations of the hard photon are considered but without interference between them. The amplitude for the final state radiation is obtained by using the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid for low energies. In real experiments the energies are never so small that ρ and ω mesons would have negligible effect. So, a phenomenological Breit-Wigner factor is introduced in the final state radiation amplitude to consider for the vector mesons influence. Using the radiation of 3π production amplitudes, a Monte Carlo event generator was developed which could be useful in experimental studies