Muon detector description as built and its simulation for the ATLAS experiment

The ATLAS detector is designed to exploit the full potential of the LHC, identifying and providing highly accurate energy and momentum measurements of particles emerging from the LHC proton–proton collisions. High-momentum final-state muons are among the most promising signatures at the LHC, thanks to a high-resolution Muon Spectrometer with standalone triggering and momentum measurement. The Muon Spectrometer is a large and complex system of gaseous detectors, requiring a detailed simulation to exploit its full capabilities. Over the last few years these systems have been described in terms of a set of geometrical primitives known as GeoModel. This description is now used in the GEANT4-based simulation program, which is fully operational and integrated into the ATLAS common analysis framework.