ATLAS Inner Detector Performance with the Rome-Initial Layout

The performance of the ATLAS Inner Detector with the Rome-Initial Layout has been studied for single muons using the Geant4 framework and the iPatRec software package. The results have been assessed and compared with those derived within the Geant3 framework for the DC1 layout. No significant change in performance as measured by transverse impact parameter or pT resolution is visible but a small decrease in longitudinal impact parameter resolution is observed, attributed to increased pixel size. Systematic shifts away from the truth, in the mean reconstructed track momentum were found during the studies. Some of these deviations are shown. An explanation for the problem has recently been found. The solution is discussed and some corrected results are shown.