Speaker
Description
During CERN LHC Run 3 data taking, the CMS Geant4-based full simulation was upgraded a few times. The Geant4 version was changed from 10.7.2 to 11.2.2. Other libraries used for the Monte Carlo simulation of CMS---CLHEP, DD4hep, VecGeom---were also updated. A new library G4HepEm was adopted for the CMS simulation, improving CPU performance both for Run 3 and Run 4. In this work, we discuss physics validation results, CPU performance, and memory consumption of the CMS full simulation, which were obtained using test beam, detector simulation, and CMS data. During Run 3, some subdetectors of CMS were added or modified mechanically. We describe these modifications and methods of geometry adoption and maintenance. The CMS geometry of Run 4 has not yet been finalized. We discuss software development for the geometry evolution and the status of the CMS Run 4 geometry description. For the Run 4 CMS full simulation, several R&D projects are ongoing, including AdePT and Celeritas GPU-based simulation of electromagnetic particle transport. We will present progress and validation results for these projects.