Simulation strategies for the LHC ATLAS experiment

The ATLAS experiment, operational at the new LHC collider, is fully simulated using a Geant 4-based simulation program within the ATLAS Athena framework. This simulation software is used for large-scale production of events on the LHC Computing Grid as well as for smaller-scale studies. Simulation of ATLAS requires many components, from the generators that simulate particle collisions to packages simulating the response of the various detectors and triggers. The latest developments in the saga of ATLAS simulation have been focussed on better representation of the real detector, based on first LHC data, and on performance improvements to ensure that event simulation is not a limiting factor in ATLAS physics analyses. The full process is constantly monitored and profiled to guarantee the best use of available resources without any degradation in the quality and accuracy of the simulation.