Numerical evaluation of virtual corrections to multi-jet production in massless QCD

TL;DR

This paper introduces a C++ library for numerically computing one-loop virtual corrections in multi-jet production in massless QCD, enabling precise NLO calculations for up to seven external partons.

Contribution

The paper presents a novel C++ library utilizing generalized unitarity for arbitrary multiplicity primitive amplitudes, facilitating accurate NLO multi-jet cross section evaluations.

Findings

Successfully applied to four jet production at NLO.

Provides a framework for up to seven external partons.

No approximation in colour is used.

Abstract

We present a C++ library for the numerical evaluation of one-loop virtual corrections to multi-jet production in massless QCD. The pure gluon primitive amplitudes are evaluated using NGluon. A generalized unitarity reduction algorithm is used to construct arbitrary multiplicity fermion-gluon primitive amplitudes. From these basic building blocks the one-loop contribution to the squared matrix element, summed over colour and helicities, is calculated. No approximation in colour is performed. While the primitive amplitudes are given for arbitrary multiplicities we provide the squared matrix elements only for up to 7 external partons allowing the evaluation of the five jet cross section at next-to-leading order accuracy. The library has been recently successfully applied to four jet production at next-to-leading order in QCD.