The ATLAS Tracking Geometry Description

Track reconstruction requires a detector geometry description for the usage in track extrapolation processes and material effects integration during track finding and track fitting. Since, in general, the more realistic detector description used in full detector simulation causes an unacceptable increase of CPU time consumption when being used in track reconstruction, the reconstruction geometry is realised as a simplified description of the actual detector layout. This documents presents the data classes of the newly developed ATLAS reconstruction geometry and describes its building process for the ATLAS CSC detector layouts. Additionally a comparison of the material budget described by the reconstruction geometry with one used in full detector simulation will be presented for the Inner Detector and the Calorimeter.