Generalised Unitarity At One-Loop With Massive Fermions

TL;DR

This paper applies generalized unitarity to compute one-loop amplitudes involving massive fermions, providing compact analytic results for specific helicity configurations and addressing divergence renormalization.

Contribution

It introduces a novel approach for calculating one-loop amplitudes with massive fermions using generalized unitarity, yielding compact analytic expressions and a method to handle divergences.

Findings

Analytic results for $tar{t}gg$ amplitude in all-plus helicity configuration.

Compact expressions achieved through a special helicity basis.

Method to fix divergences using universal UV and IR behaviour.

Abstract

We describe an application of generalised unitarity to the computation of one-loop amplitudes with massive external fermions. We present analytic results for the cut-constructible parts of the leading colour contributions to the all-plus helicity configuration of the $t\bar{t}gg$ amplitude. Using a special choice for the helicity basis of the massive fermions we are able to obtain extremely compact analytic expressions. In particular we describe how one can fix the divergent contributions from tadpole and wave-function renormalisation using universal UV and IR behaviour.