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

Physics beyond the Standard Model (BSM), such as supersymmetric models, predicts long-lived charged particles (LLPs). If produced at the LHC, such states are expected to traverse part of the ATLAS detector before decaying into a stable neutral particle, leaving a disappearing track (tracklet). These particles are expected to produce unusually large specific ionization (dE/dx) in silicon compared with Standard Model minimum-ionizing particles. Motivated by this signature, we aim to evaluate whether dE/dx behavior is accurately captured in simulation. We study dE/dx for tracks and tracklets in Z→μ⁺μ⁻ collision data and inclusive QCD-dijet simulations to test whether momentum-dependent energy-loss patterns are consistently reproduced. To limit detector-interaction effects and kinematic biases, a simple momentum–ionization zoning approach is applied. Together, these elements provide a coherent basis for comparing data and simulation in regimes relevant to searches for charged LLPs.