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Manuscript Title: High-energy-physics event generation with PYTHIA 5.7 and JETSET 7.4.
Authors: T. Sjostrand
Program title: PYTHIA 5.7 AND JETSET 7.4
Catalogue identifier: ACTU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 82(1994)74
Programming language: Fortran.
Computer: IBM 9000.
Operating system: VM/ESA, Unix.
RAM: 420K words
Word size: 32
Keywords: Particle physics, Elementary, Event simulation, Standard model, Beyond standard model, Hard scattering, E+e- annihilation, Leptoproduction, Photoproduction, Hadronic processes, High-p scattering, Prompt photons, Gauge bosons, Higgs physics, Parton distribution Functions, Jet production, Parton showers, Fragmentation, Hadronization, Beam remnants, Multiple interactions, Particle decays, Event measures.
Classification: 11.2.

Nature of problem:
High-energy collisions between elementary particles normally give rise to complex final states, with large multiplicities of hadrons, leptons, neutrinos and photons. The relation between these final states and the underlying physics description is not a simple one, for two main reasons. Firstly, we do not even in principle have a complete understanding of the physics. Secondly, any analytical approach is made untractable by the large multiplicities.

Solution method:
Complete events are generated by Monte Carlo methods. The complexity is mastered by a subdivision of the full problem into a set of simpler separate tasks. All main aspects of the events are simulated, such as hard-process selection, initial- and final-state radiation, beam remnants, fragmentation, decays, and so on. Therefore events should be directly comparable with experimentally observable ones. The programs can be used to extract physics from comparisons with existing data, or to study physics at future experiments.

At very high energies the program may break down for one of two reasons: either the number of particles may exceed the memory space available, or the (mainly) single-precision kinematics may give unacceptable roundoff errors. Many physics restrictions exist, as already noted.

Unusual features:

Running time:
1-100 events per second, depending on process studied.