Collier: a fortran-based Complex One-Loop LIbrary in Extended Regularizations

TL;DR

Collier is a Fortran library designed for the numerical evaluation of one-loop scalar and tensor integrals in quantum field theories, supporting complex masses and various regularization schemes.

Contribution

It introduces a comprehensive Fortran-based tool capable of handling complex masses and multiple regularization methods for one-loop integrals in quantum field theory.

Findings

Supports arbitrary tensor and scalar integrals for scattering processes

Handles complex masses and regularization schemes

Provides numerical results for various quantum field theory calculations

Abstract

We present the library Collier for the numerical evaluation of one-loop scalar and tensor integrals in perturbative relativistic quantum field theories. The code provides numerical results for arbitrary tensor and scalar integrals for scattering processes in general quantum field theories. For tensor integrals either the coefficients in a covariant decomposition or the tensor components themselves are provided. Collier supports complex masses, which are needed in calculations involving unstable particles. Ultraviolet and infrared singularities are treated in dimensional regularization. For soft and collinear singularities mass regularization is available as an alternative.