Performance reconstruction of eco-friendly gas mixtures for improved resistive plate Chambers at GIF++ using Geant4

Abstract A reconstruction is developed to infer the performance of CMS improved Resistive Plate Chambers (iRPC) using Geant4 observables and one experimental anchor. The Geant4 energy deposition is used to estimate the primary ionization yield, while the efficiency is modeled through an induced charge description encoded in an effective gain G ( E ). The absolute scale is fixed by calibrating the standard CMS mixture to the experimentally measured efficiency curve of the detector at GIF++ under defined irradiation conditions, and extracting macroscopic Townsend parameters. The same procedure is propagated to four alternative mixtures, including two tetrafluoropropene (HFO-1234ze, hereafter HFO) and CO 2 eco-friendly blends, to reconstruct efficiency curves and working points. The framework focuses on efficiency observables (sensitivity and effective gain) and provides rapid estimates of gain, sensitivity and efficiency for initial mixture studies without requiring dedicated experimental measurements.