Introduction#
New projects in High Energy Physics (HEP) and upgrades to existing ones promise new discoveries but at the cost of increased hardware complexity and data readout rates. Deducing new physics from detector readouts requires a proportional increase in computational resources. The High Luminosity Large Hadron Collider (HL-LHC) detectors will require more computational resources than are available with traditional CPU-based computing grids. For example, the CMS collaboration forecasts [20221f] that when the upgrade is brought online, computational resource requirements will exceed availability by more than a factor of two, about 40% of which is Monte Carlo (MC) detector simulation, without substantial research and development improvements.
Celeritas [1] is a new MC particle transport code designed for high performance simulation of complex HEP detectors on GPU-accelerated hardware. Its immediate goal is to simulate electromagnetic (EM) physics for LHC-HL detectors with no loss in fidelity, acting as a plugin to accelerate existing Geant4 [AAA+03] workflows by “offloading” selected particles to Celeritas to transport on GPU.
This user manual is written for three audiences with different goals: Geant4 toolkit users for integrating Celeritas as a plugin, advanced users for extending Celeritas with new physics, and developers for maintaining and advancing the codebase.