1) Results of BDSIM and capabilities of the tools -- John Carter
2) Moving from Geant 3 to Geant 4 -- Takashi Maruyama


John and Takashi presented possible approaches to modeling the beam delivery system and detector components.

The BDSIM tool described by John is a C++, Geant4 based toolkit providing fast tracking through accelerator components, has all physics processes from Geant4 and is currently looking to improve handling of neutron processes, takes optics as MAD format, can track bunch and halo particles or Guinea-Pig disrupted beam or pairs. BDSIM can perform collimation studies, can evaluate background levels at any point along the beam line, etc. Complicated geometries of Interaction Region can be built using MySQL database, linking BDSIM to detector studies.

Takashi described the need to move from Geant3 to Geant4, for BDS/Detector simulations, and the issues associated with this transition, in particular that the geometry need to be C++ coded. One possible solution is to use SLIC (Simulator for Linear Collider) which is Geant4 based, and where geometry is described by LCDD (linear collider detector description) XML file. There are however several functionalities missing in SLIC (such as tracking in real solenoid field) which however already built in in BDSIM.

The group then engaged into discussion of the way to proceed. Clearly, it is unavoidable and beneficial to have several tools that could be cross checked. The benefits to have a common detailed description of the optics and detector, that could be parsed and fed to BDSIM, SLIC, MARS, etc., is obvious. But one should not also forget that too detailed models are not always necessary, and simplified yet accurate models may be required (e.g. for magnetic calculations). As a first step to solving these questions we agreed that smaller group of people will discuss how BDSIM/SLIC/MARS can benefit from each other and if some common description can be used. We will hear from this subgroup in about three weeks. 

Andrei Seryi, 07/13/05