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Manuscript Title: Automatic generation of tree level helicity amplitudes.
Authors: T. Stelzer, W.F. Long
Program title: MadGraph
Catalogue identifier: ACTX_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 81(1994)357
Programming language: Fortran.
Computer: DEC.
Operating system: UNIX, VMS.
RAM: 3000K words
Keywords: Feynman diagrams, Feynman helicity Amplitudes, Automatic code generation, Helas.
Classification: 4.4, 11.5.

Nature of problem:
Calculation of higher order tree level Feynman helicity amplitudes which involve several external particles can require the evaluation of hundreds of Feynman diagrams. Hand coding programs to compute these amplitudes is very time consuming and error-prone. For complex problems the widely used packages based on symbolic mathematics systems either produce inefficient code or fail because of excessive memory or CPU requirements.

Solution method:
A program, MadGraph, was written in Fortran to accept a simple description of the desired process and create a Fortran function subprogram in either f77 or f90 syntax which will compute the specified amplitude by making calls to subroutines in the HELAS package. MadGraph also produces a postscript file with drawings of all the included Feynman diagrams.

[1] A HELAS manual giving detailed descriptions of the routines is freely available from the authors (e-mail address: long@phenob.physics.wisc.edu)