Test of FSR in the process $e^+e^-\toπ^+π^-γ$ at DA$Φ$NE and extraction of the pion form factor at threshold

Abstract

Effects due to non-pointlike behaviour of pions in the process $e^+e^-\toπ^+π^-γ$ can arise for hard photons in the final state. By means of a Monte Carlo event generator, which also includes the contribution of the direct decay $ϕ\toπ^+π^-γ$, we estimate these effects in the framework of Resonance Perturbation Theory. We consider angular cuts used in the KLOE analysis of the pion form factor at threshold. A method to reveal the effects of non-pointlike behaviour of pions in a model-independent way is proposed.