Measurement of the pion form factor at KLOE with photons at small angle

Abstract

The KLOE experiment at the DAΦNE ϕ-factory in Frascati performs a measurement of the cross section e + e − → π + π − using Initial State Radiation events, known as radiative return method. Here we present work in progress to improve the published result which used photons emitted at small polar angles without requiring their explicit detection (no photon tagging). In particular, a possibility to normalize the cross section using μμγ events is discussed. The knowledge of the μμγ cross section also allows to test the initial state radiator function.