PROGRAM SUMMARY
Title of program:
HELAC
Catalogue identifier:
ADMS
Ref. in CPC:
132(2000)306
Distribution format: tar gzip file
Operating system: Unix
Number of lines in distributed program, including test data, etc:
65726
Keywords:
Elementary particle physics, Quantum Chromodynamics,
Automatic evaluation of helicity amplitudes, Dyson-Schwinger
equations, Recursive algorithms.
Programming language used: Fortran
Computer:
ALPHA workstation ,
HP workstation ,
IBM workstation .
Nature of problem:
A substantial part of particle phenomenology nowadays is based upon our
ability to study efficiently processes involving a relatively large
number of particles. This requires efficient algorithms for matrix
element calculation and phase space generation and integration. As far
as the matrix element calculation is concerned, the traditional approach
utilizes standard Feynman graph representation of the scattering
amplitude, resulting to a computational cost that grows asymptotically
as n!, where n is the number of particles involved in the process.
Method of solution:
As alternative recursive algorithms based on Schwinger-Dyson equations
lead asymptotically to a much lower growth of the computational cost,
namely a**n, where a ~ 3, it is the aim of this paper to present such an
algorithm as well as the corresponding Fortran code which allows the
computation of any tree-order electroweak amplitude.