Methodology for measuring the transition electromagnetic form factor in the conversion decay ω → π0e+e– with the CMD-3 detector

This paper presents an improved methodology for measuring the transition electromagnetic form factor in the conversion decay ω → π0e+e– using data collected by the CMD-3 detector at the VEPP-2000 e+e– collider. The key improvement involves the application of a kinematic reconstruction technique under two distinct hypotheses: the signal hypothesis (ω → π0e+e–) and the dominant background hypothesis (ω → π+π–π0). This approach allows for a powerful suppression of 3π background, virtually eliminating it, and significantly narrows the invariant mass distribution of two photons from π0 decay in signal events. The refined π0 mass peak enhances the separation of the signal process from the remaining QED background (e+e– → e+e–γγ). To demonstrate the effectiveness of the method, it was applied to a subset of the data with an integrated luminosity of 13 pb⁻¹, accumulated near ω-meson mass. The analysis shows a significant improvement in the precision of the form factor F(q) measurement. The developed methodology paves the way for a more precise determination of the form factor slope parameter Λ ω−2 when applied to the full dataset, which has an integrated luminosity of approximately 50 pb⁻¹.