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Manuscript Title: The Lund Monte Carlo for e+e- jet physics.
Authors: T. Sjostrand
Program title: JETSET 4.3 E
Catalogue identifier: AAVM_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 28(1983)229
Programming language: Fortran.
Computer: ND-50.
Operating system: SINTRAN III/VS.
RAM: 37K words
Word size: 32
Keywords: Elementary, Particle physics, Event simulation, E+e- annihilation, Jet fragmentation, Monte carlo simulation, Sphericity, Thrust, Cluster analysis.
Classification: 11.2.

Subprograms used:
Cat Id Title Reference
AAVJ_v1_0 JETSET 4.3 G CPC 27(1982)243

Other versions:
Cat Id Title Reference
AAVJ_v1_0 JETSET 4.3 G CPC 27(1982)243
AAFP_v1_0 JETSET 6.2 CPC 39(1986)347
AAFP_v2_0 JETSET 6.3 CPC 43(1987)367
ACTU_v1_0 PYTHIA 5.7 AND JETSET 7.4 CPC 82(1994)74

Nature of problem:
In high energy e+e- annihilation events a large number of particles are to be found in the final state. These particles are not uniformly distributed in space, but rather concentrated into a few jets. In QCD, the candidate theory of strong interactions, this is understood as the creation of a small number of quarks and gluons in the primary interaction, which then hadronize to give the jets. However, the mechanism of this hadronization is not well understood. Experimentally, it is then difficult to disentangle the perturbative aspects of QCD from the hadronization ones.

Solution method:
Matrix elements obtained in perturbative QCD and QFD (the standard SU(2)*U(1) theory of weak and electromagnetic interactions) are implemented to give a description of the production of different quark flavours, the emission of gluons and the angular orientation of partons. The program presented in a companion paper is then used to take care of the jet fragmentation and particle decays. This way, we generate complete events that can be directly compared with experimental data. To help characterize these events, we also implement the ordinary sphericity and thrust measures and present a new cluster algorithm.

Restrictions:
Only leading order QFD and first order QCD (second order QCD if the user supplies virtual corrections) are implemented. Radiative corrections are not included, but can be added.

Unusual features:
A random number generator is required.

Running time:
The matrix element treatment (i.e. the parts presented in this paper ) of a continuum event at 40 GeV takes 0.015 s if four-jet events are not included and 0.03 s if they are. The subsequent jet fragmentation and particle decays take 0.25 s. For a toponium event at 40 GeV matrix element treatment again takes 0.015 s and the subsequent hadronization 0.35 s. Times for sphericity, thrust and cluster analysis of 40 GeV events are 0.02, 0.15 and 0.3 s, respectively. The time for four-jet treatment depends strongly on the energy, making inclusion of four-jet events quite time-consuming at higher energies, while time for hadronization and event analysis is roughly linear in multiplicity and hence slowly increasing with the energy.