Material budget studies in the ALICE central barrel using proton production asymmetry

A differential analysis is performed to investigate an observed overabundance of protons relative to antiprotons in ALICE Time Projection Chamber (TPC) data when compared to Monte Carlo (MC) simulations. Two event generators, PYTHIA and EPOS, are employed to model Pb–Pb collisions and to provide reconstructed MC samples for direct comparison with experimental data. Proton identification in both data and MC is based on TPC specific energy loss (dE/dx) and track-quality selections. The first stage of the analysis focuses on pseudorapidity distributions and yield ratios of protons to antiprotons. The second stage identifies the spatial and material origin of protons and antiprotons in the MC simulations using detailed detector geometry information. The comparison indicates a pronounced proton-antiproton imbalance in data that is not reproduced by the simulations.