In order to track particles through the NA49 detector system, a code called GNA49 was constructed
based on the GEANT package.
The tracking incorporates all relevant physical processes such as the decay of unstable particles,
multiple scattering of charged
particles, and production of secondary particles by inelastic reactions with detector materials.
GNA49 includes a detailed description of the geometry and materials of the
detector system along with many utility routines, including routines for generating input particles
with a variety of momentum distributions.
Tracks generated by GNA49 consist of a list of idealized space points at the track intersections
with the vertical planes defined by the TPC readout pad rows.
Each space point records the spatial coordinates at the point of intersection, the momentum
components of the particle at that position, and the ionization energy loss
the particle suffered within the pad row.
To run GEANT we must have an input file. It can be of two kinds: from a simple simulation ("Micky Mouse")
in ASCII format or from a model such as UrQMD or Venus
in DSPACK format.
More informations about GEANT you may find
Below are the major components of this program described step-by-step: