Speaker
Description
Accurate modelling of charge sharing and pixel response is essential for evaluating the performance of the Circular Electron–Positron Collider (CEPC) vertex detector, particularly for tracks at large incident angles. We present an Allpix²-based simulation and digitization workflow for TaichuPix monolithic active pixel sensors developed for CEPC, with an emphasis on the processes connecting particle energy deposition to reconstructed pixel clusters.
The workflow combines Geant4 energy deposition, electron and hole transport through imported three-dimensional electric-field maps, Shockley–Ramo signal induction, and threshold-based digitization incorporating electronic noise and threshold dispersion. Simulations of 2.5 GeV electrons at incident angles from 0° to 80° relative to the sensor normal are used to investigate charge collection, lateral charge sharing, hit efficiency, and cluster-size distributions. Comparisons with beam-test measurements provide experimental benchmarks for assessing the angular dependence of the simulated response.
Particular attention is given to the consistency between collected charge, induced signals, and the threshold decision. Controlled studies examine the effects of collection geometry, carrier termination at sensor boundaries, transport time step, and signal integration. An idealized continuously active discriminator response is also implemented to study threshold crossing during pulse development. These diagnostics identify simulation assumptions that can substantially affect the predicted cluster multiplicity and help distinguish transport effects from signal-formation and digitization effects.
We discuss the current simulation-to-data comparisons, remaining discrepancies, and priorities for further validation. This work provides a reproducible basis for refining TaichuPix digitization and supporting future studies of the CEPC vertex-detector response.
