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Manuscript Title: Numerical calculation of helicity amplitudes for processes involving massive fermions.
Authors: H. Tanaka
Program title: CHANEL
Catalogue identifier: ABLT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 58(1990)153
Programming language: Fortran.
Computer: FACOM M780.
Operating system: OSIV/F4 MSP, VOS3.
RAM: 650K words
Word size: 32
Keywords: General purpose, Diagramatic expansions, Particle physics, Elementary, Helicity amplitude, Electroweak theory, Qed, Event generator.
Classification: 4.4, 11.4.

Nature of problem:
In high energy physics, it is important to evaluate higher order contributions. However, calculations of higher order corrections are quite complicated in the framework of the standard method based on squaring the amplitudes and summing over spin states. More efficient ways to calculate cross sections for complicated sets of Feynman diagrams are desired.

Solution method:
A simple method for exact calculation of scattering amplitudes is proposed. In the method presented in this paper, Feynman amplitudes are decomposed to vertex amplitudes by rewriting the numerators of propagators into wave functions of spinor fields and polarization vectors of gauge bosons, and these amplitudes are evaluted numerically. It is found that the resultant expressions are compact and lend themselves to fast numerical evaluation.