Multi-gluon one-loop amplitudes numerically

TL;DR

This paper presents a C++ implementation of a numerical algorithm for evaluating one-loop multi-gluon amplitudes in QCD, addressing stability and extending to arbitrary gluon numbers.

Contribution

It introduces a new C++ code for the D_s-dimensional unitarity cut method to compute virtual NLO QCD amplitudes with multiple gluons.

Findings

Achieved numerical stability in calculations.

Validated results against existing literature.

Extended capabilities to arbitrary gluon numbers.

Abstract

A c++ implementation of the D_s-dimensional unitarity cut algorithm for the numerical evaluation of the virtual contribution to NLO QCD amplitudes is presented. The current version includes an arbitrary number of external gluons with gluonic propagators in the loop. The building blocks are tree level color-ordered amplitudes with gluons and with gluons and two scalars in five dimensions. Numerical stability issues are addressed and agreement has been reached with the results published in the literature.