Improvement in the 3D shower shapes description in the Monte Carlo simulation for a lead-scintillating fiber electromagnetic calorimeter

Background The lead-scintillating fiber electromagnetic calorimeter (ECAL) of the Alpha Magnetic Spectrometer measures the energy of positrons/electrons and separates them from hadrons. The electromagnetic shower shapes from Monte Carlo (MC) simulation and data show disagreement. Purpose Tuning the MC to make the shower shapes from MC and data agree with each other. Methods The tuning is based on a 3D electromagnetic shower model. Results After tuning, the electromagnetic shower shapes are well described by MC up to TeV. As a result, the output of ECAL electron/proton separation estimator, ECAL BDT, shows that MC and data are in good agreement. The proton rejection power of the ECAL BDT trained with MC electron samples is improved by a factor of 5 at ∼ 800 GeV compared to the one trained with data.