Readiness of the CMS detector simulation

The porting of the GEANT4 based CMS simulation application to the newly re-engineered CMS software framework has been completed and extensively validated from almost 250 million physics events generated during 2006-2007 for several commissioning, software, and physics validation challenges. The focus is currently centered on improving and validating the geometry description, and the physics modeling from comparisons with test beam, magnet tests, and cosmic ray data. Software robustness and time performance, as well as the development of tools toward a data driven, tunable, Monte Carlo are also areas of significant activity. In this paper, we describe the basic elements of the CMS simulation application within the new architecture, the progress toward an accurate modeling of geometry, interaction of particles with matter, magnetic field, and electronic processing. We also describe the different tools to make the simulation more realistic and data based, as well as the results from the most recent robustness and time performance tests.