Status of shower parameterisation Marc Verderi LLR – Ecole polytechnique Bordeaux, 9th Nov. 2005

Recent past/current news ATLAS discovered a problem in stepping Made the “exclusive force” flag not working properly in some situations Now fixed and released Migration to region Fast simulation code migrated to G4Region Fast simulation models are now attached to the G4Region (through a G4FastSimulationManager), thanks to Makoto. They used to be attached to an “envelope” (a G4LogicalVolume, root of a volume hierarchy tree) Envelope and region are close/same concept Still, example N05 needs to be updated Must be done quickly Migration to region implies some changes of the user code: For what concerns informations related to the “envelope” Change of G4LogicalVolume → G4Region GFlash code migrated to G4Region as well, by Joanna

About gflash in G4 Work undertaken by Joanna Weng Motivated by CMS needs Concrete EM shower parameterisation H1 fortran code, re-engineered to G4 Up to 2 order of magnitudes speed-up in “block” geometries  But only factor ~<5 in realistic geometries  Many parts left to detailed tracking Many calls to trigger methods of fast simulation returning “false” : ie no parameterisation Case of low energy particles in shower Investigate what optimization could be done on fast simulation code side Like “forget” a track Or “forget track and daughters” Limited gain expected ?

Future developments The “ghost volumes” capability was part of the requirements for the “parallel geometry” development “ghost volumes” are used to define regions in which a fast simulation can be triggered, having this ghost volumes independent of the tracking geometry These geometry are “flavored” : ie defined for given particle types A parallel navigation is provided currently by the fast simulation process But complications arise in case of a presence of a magnetic field The general parallel navigation capability should solve this Fast simulation will be migrated to this general framework when available Will/should consist mainly of changes in the fast simulation process. Informal parallel session on this topic this afternoon 17:00 – 18:15