CutTools: a program implementing the OPP reduction method to compute one-loop amplitudes

TL;DR

CutTools is a software tool that efficiently computes one-loop amplitudes in quantum field theory by implementing the OPP reduction method, handling rational terms and numerical instabilities adaptively.

Contribution

It introduces a practical implementation of the OPP reduction method for one-loop amplitude calculations, including rational term computation and stability enhancements.

Findings

Successfully computes one-loop scalar integral coefficients

Handles rational terms from 4D and epsilon-dimensional parts

Employs adaptive precision to mitigate numerical instabilities

Abstract

We present a program that implements the OPP reduction method to extract the coefficients of the one-loop scalar integrals from a user defined (sub)-amplitude or Feynman Diagram, as well as the rational terms coming from the 4-dimensional part of the numerator. The rational pieces coming from the epsilon-dimensional part of the numerator are treated as an external input, and can be computed with the help of dedicated tree-level like Feynman rules. Possible numerical instabilities are dealt with the help of arbitrary precision routines, that activate only when needed.