AtlFast3 is the new, high-precision fast simulation in ATLAS that was deployed by the collaboration to replace AtlFastII, the fast simulation tool that was successfully used for most of Run2. AtlFast3 combines a parametrization-based Fast Calorimeter Simulation and a new machine-learning-based Fast Calorimeter Simulation based on Generative Adversarial Networks (GANs). The new fast simulation can reproduce the Geant4 inputs with higher accuracy than the old AtlFast2. In particular, the simulation of jets of particles reconstructed with large radii and the detailed description of their substructure are significantly improved in AtlFast3. Results will be presented on the performance of the new AtlFast3 that will be deployed for the simulation of the majority of events in Run3; these changes are crucial for achieving the precision needed by analyses that will need to rely mainly on fast simulation.
|Consider for long presentation||No|