APACIC++ 1.0, A parton cascade in C++. R. Kuhn, F. Krauss, B. Ivanyi, G. Soff.

PROGRAM SUMMARY
Title of program: APACIC++, version 1.0
Catalogue identifier: ADNE
Ref. in CPC: 134(2001)223
Distribution format: tar gzip file
Operating system: UNIX, LINUX, VMS
Number of lines in distributed program, including test data, etc: 29710
Keywords: Elementary particle physics, Event simulation, Standard model, Gauge bosons, Higgs-boson physics, e+e- annihilations, Jet production, Parton shower.
Programming language used: C++, Fortran

Nature of physical problem:
With rising energies, the final state in high-energy electron positron-annihilations becomes increasingly complex. The number of jets as well as the number of observable particles, leptons, hadrons and photons, increases drastically and prevents any analytical prediction of the full final state. In addition, the transformation of the partons of perturbative quantum field theory into the experimentally observable hadrons is so far not understood on a quantitative level. Both obstacles prevent any attempt to bring the fundamental theory in direct contact with the final states by analytical methods.

Method of solution:
APACIC++ produces complete e+e- -events on a level suitable for direct comparison with experiment. The events are generated using Monte-Carlo methods and by dividing their simulation into well-separated steps. APACIC++ concentrates in its event generation on the hard subprocess producing jets and the subsequent parton shower describing their evolution. For the production of jets, interfaces to various matrix element generators are provided. The fragmentation into hadrons and their subsequent decays are left for well-defined models encoded in already existing Fortran programs. Suitable interfaces are supplemented.