Analysis of the background on cross section measurements with the MAGNEX spectrometer: The (20Ne, 20O) Double Charge Exchange case - Calabrese, S; Borello-Lewin, Thereza; Medina, Nilberto Heder; Oliveira, José Roberto Brandão de (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020)