Study of the A/H -> mumu channel in the Muon Spectrometer with GEANT4 and comparison with ATLFAST

This note documents the first attempt at using Geant4 for the ATLAS Muon Spectrometer full simulation. The development of the code for the detailed description of MDTs, RPCs and TGCs and for the connection to the reconstruction program MUONBOX allows for testing the Muon Spectrometer simulation on physics events, in view of the next Data Challenges. The A/H -> mu mu physics channel is chosen as a benchmark, since dimuon final state identification and reconstruction may be performed with high efficiency by using the standalone Muon System. Events fully simulated and reconstructed within the Geant4 framework are evaluated and subsequently compared to the results obtained with the ATLFAST fast simulation program. The same kinematic selections have been applied to both event samples so as to be able to compare the final results. A good agreement is found for both the reconstruction efficiency and the signal acceptance. This work represents the first step towards the Geant4 full simulation of the ATLAS detector and its performance.