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Manuscript Title: A Monte Carlo program for generating hadronic final states.
Authors: L. Angelini, M. Pellicoro, L. Nitti, G. Preparata, G. Valenti
Program title: FIRST
Catalogue identifier: ACBR_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 67(1991)293
Programming language: Fortran.
Computer: VAX.
Operating system: VAX-VMS, VM-CMS.
RAM: 366K words
Word size: 32
Keywords: Particle physics, Elementary, Event simulation, Monte carlo, Qgd/acd, Hadronic final states, Event generator.
Classification: 11.2.

Nature of problem:
Hadronic final states, originating from high energy collisions, show a high degree of universality in both physical composition and geometrical structure, thus suggesting a common underlying dynamics. A theoretical model, based on Quark-Geometro-Dynamics and Anisotropic-Chromo-Dynamics (QGD/ACD) and extensively developed in the last years is able to explain this relevant feature using highly excited quark-antiquark bound states (confined), called FireStrings (FS). The model assumes that the colliding particles in the initial state (lepton-lepton, lepton-hadron, hadron-hadron, etc.) give rise to an intermediate state in which one or more FS's get formed together with a few number of other particles (leading clusters, etc.). The evolution and the decay of each FS are responsible for the deposition of hadrons in the final state.

Solution method:
FIRST is a computer program for handling the decay of both the FS's and the unstable particles produced in the intermediate states. An earlier version (EPOS) was implemented for handling the electron-positron annihilation at high energies. FIRST uses the Monte Carlo method and generates events with weight = 1. The FS-decay occurs through a multi- step process arising from an iterative decay scheme. The process continues until the whole FS-mass has been converted into known hadrons. The particle decay is implemented using either the experimentally known branching ratios or, in absence of experimental information, theoretical predictions. The routines necessary to generate events in e+e- annihilation, have also been included in the package.

FIRST does not include a main program, which must be provided by the user in order to produce the FS's and/or other particles starting from the initial state.

Running time:
The mean running time for one event on a micro Vax 3800 is: 85 ms at W = 10 GeV, 160 ms at W = 50 GeV and 240 ms at W = 90 GeV.