FAMOS: A Dynamically Configurable System for Fast Simulation and Reconstruction for CMS

Detailed detector simulation and reconstruction of physics objects at the LHC are very CPU intensive and hence time consuming due to the high energy and multiplicity of the Monte-Carlo events and the complexity of the detectors. We present a dynamically configurable system for fast Monte-Carlo simulation and reconstruction (FAMOS) that has been developed for CMS to allow fast studies of large samples of Monte-Carlo events. Each single step of the chain - simulation, digitization and reconstruction, as well as combinations of chain links can be replaced by modules that sacrifice precision for speed. Fast and detailed modules have identical interfaces so that a change is fully transparent for the user. Currently, a complete set of the fastest possible implementation, i.e. going directly from the Monte-Carlo truth to reconstructed objects, has been implemented. It is about hundred to thousand times faster than the fully detailed simulation/reconstruction and provides tracks reconstructed by the inner tracker, clusters in calorimeters and trigger-Lvl1 objects and tracks reconstructed for the muon system of the CMS detector.