Test of FSR in the process $e^+e^-\toπ^+π^-γ$ at DA$Φ$NE

Abstract

In this paper we consider the possibility to test the FSR model in the reaction $e^+e^-\toπ^+π^-γ$ at DA$Φ$NE. We propose to consider the low $Q^2$ region ($Q^2$ is the invariant mass squared of the di-pion system) to study the different models describing $gamma^*\toπ^+π^-γ$ interaction. As illustration we compare the scalar QED and Resonance Perturbation Theory prediction for the $e^+e^-\toπ^+π^-γ$ cross section. We also consider the contribution coming from the $ϕ$ direct decay ($ϕ\toπ^+π^-γ$). We find the low $Q^2$ region is sensitive to FSR models.