Investigating the dE/dx Response of the ATLAS Simulation for Long-Lived Charged Particle Searches

Physics beyond the Standard Model (BSM), including supersymmetry, predicts long-lived charged particles (LLPs). If produced at the LHC, such states may traverse part of the ATLAS detector before decaying leaving a disappearing track (tracklet). They are also expected to produce unusually large specific ionization (dE/dx) relative to Standard Model minimum-ionizing particles. Motivated by this signature, we wish to characterize the dE/dx modeling of Monte Carlo simulation. To do this, we analyze the dE/dx response of tracks and tracklets in data and from simulation. Z→μ⁺μ⁻ collision data is compared with QCD-dijet simulation, and the consistency of energy-loss patterns is assessed across tracks and tracklets.To ensure the simulation is accurate across different kinematic regions, a simple transverse-momentum and ionization zone scheme is employed; in parallel, Pixel cluster topology is studied across layers of the detector. . Together, these elements provide a coherent basis for comparing data and simulation in regimes relevant to charged-LLP searches.