Two sets of parameterized models are provided for the simulation of high
energy hadron-nucleus interactions. The so-called ``low energy model'' is
intended for hadronic projectiles with incident energies between 1 GeV and
25 GeV, while the ``high energy model'' is valid for projectiles between 25
GeV and 10 TeV. Both are based on the well-known GHEISHA package of GEANT3.
The physics underlying these models comes from an old-fashioned multi-chain
model in which the incident particle collides with a nucleon inside the
nucleus. The final state of this interaction consists of a recoil nucleon,
the scattered incident particle, and possibly many hadronic secondaries.
Hadron production is approximated by the formation zone concept, in which the
interacting quark-partons require some time and therefore some range to
hadronize into real particles. All of these particles are able to re-interact
within the nucleus, thus developing an intra-nuclear cascade.
In these models only the first hadron-nucleon collision is simulated in detail. The remaining interactions within the nucleus are simulated by generating additional hadrons and treating them as secondaries from the initial collision. The numbers, types and distributions of the extra hadrons are determined by functions which were fitted to experimental data or which reproduce general trends in hadron-nucleus collisions. Numerous tunable parameters are used throughout these models to obtain reasonable physical behavior. This restricts the use of these models as generators for hadron-nucleus interactions because it is not always clear how the parameters relate to physical quantities. On the other hand a precise simulation of minimum bias events is possible, with significant predictive power for calorimetry.