Defining the Detector Geometry

The definition of the detector geometry happens in two steps, as usual in Geant. First the materials have to be defined, then the actual geometry. The master routine called by GEANT is UGEOM. Logically the detector is divided into four volumes:

• cave: the master volume, which encloses all other volumes.
• inner detector, volume CDET: all detector elements which are inside the coil, including the coil itself.
• outer detector, volume ODET: all detector elements which are outside the coil.
• machine, volume MACH: all detector elements which are connected to the machine: beampipe, beamline elements, etc.

The structure of this logical subdivision is mirrored by separate subroutines, which build the different detector parts. Each of these routines then in turn calls one routine for every subdetector.