Simulation strategies using FATRAS and Geant4 for a future upgrade of the ATLAS tracking detectors

With the completion of installation and commissioning of the ATLAS detector in 2008, the collaboration has increased its effort focussing on the upgrade of the ATLAS detector devices that should take place in parallel to a luminosity upgrade of the Large Hadron Collider (LHC). The upgrade of the ATLAS tracking detector will be performed in two steps, starting from the insertion of a new innermost pixel silicon layer to a full replacement of the inner tracking devices. Design decisions based on Monte Carlo simulation are necessary within the near future to allow hardware research and development and finally to guarantee a completion of the detector construction until the planned intervention periods.