Validation of the GEANT4-Based Full Simulation Program for the ATLAS Detector: An Overview of Performance and Robustness

This paper gives an overview of the validation tests of the ATLAS GEANT4 simulation package G4ATLAS, which were performed in the period from fall 2003 until the end of 2004. This spans the time from first comprehensive tests after G4ATLAS had been fully embedded into the ATLAS common framework in its full functionality and detail, the time of its development into a highly reliable, performant and robust tool, up to its extremely successful usage in ATLAS Data Challenge 2 (DC2) and (Combined) Testbeam simulation productions. In DC2, more than 12 million full physics events were successfully simulated in a world-wide, distributed way. During that validation phase, G4ATLAS became widely accepted as the simulation package for ATLAS.The paper describes in some detail the testing period from its beginning (ATLAS offline release 7.1.0) until arriving at a stable version of G4ATLAS for DC2 (release 8.0.5), and presents results from performance tests carried out after DC2 and in the context of (Combined) Testbeam simulation.