Golem95C: A library for one-loop integrals with complex masses

TL;DR

This paper introduces Golem95C, a numerical library for evaluating one-loop scalar and tensor integrals with complex masses, supporting algebraic and unitarity-based methods, and avoiding inverse Gram determinants.

Contribution

Golem95C extends previous libraries by enabling complex mass support and improved numerical stability in one-loop integral calculations.

Findings

Supports complex masses in one-loop integrals

Avoids inverse Gram determinants for stability

Applicable to algebraic and unitarity-based methods

Abstract

We present a program for the numerical evaluation of scalar integrals and tensor form factors entering the calculation of one-loop amplitudes which supports the use of complex masses in the loop integrals. The program is built on an earlier version of the golem95 library, which performs the reduction to a certain set of basis integrals using a formalism where inverse Gram determinants can be avoided. It can be used to calculate one-loop amplitudes with arbitrary masses in an algebraic approach as well as in the context of a unitarity-inspired numerical reconstruction of the integrand.