LanHEP - a package for automatic generation of Feynman rules in field theory. Version 2.0
A. V. Semenov
TL;DR
LanHEP 2.0 automates the generation of Feynman rules directly from a user-defined Lagrangian, producing consistent momentum-space vertices in CompHEP formats or LaTeX tables. It supports QED, QCD, and MSSM-compatible features, including supersymmetric superpotentials, BRST invariance checks, ghost terms, and advanced vertex handling such as splitting of 4-fermion/4-color interactions via auxiliary fields. The framework emphasizes index management, two-component fermion formalisms, and extensive validation workflows (charge conservation, Hermitian conjugates, mass terms, BRST) to minimize manual errors in complex theories. With modular input, flexible indexing, and LaTeX/CompHEP outputs, LanHEP enables rapid exploration and verification of extended models, including MSSM and beyond, while providing tools for simplification and visualization of vertices.
Abstract
The LanHEP program for Feynman rules generation in momentum representation is presented. It reads the Lagrangian written in a compact form, close to the one used in publications. It means that Lagrangian terms can be written with summation over indices of broken symmetries and using special symbols for complicated expressions, such as covariant derivative and strength tensor for gauge fields. The output is Feynman rules in terms of physical fields and independent parameters. This output can be written in LaTeX format and in the form of CompHEP model files, which allows one to start calculations of processes in the new physical model. Although this job is rather straightforward and can be done manually, it requires careful calculations and in modern theories with many particles and vertices, such as supersymmetric models, can lead to errors and misprints. The program allows one to introduce into CompHEP new gauge theories as well as various anomalous terms.