Factorisation and Subtraction beyond NLO

TL;DR

This paper introduces a general method for constructing local infrared subtraction counterterms applicable to any order in perturbation theory, simplifying higher-order calculations of differential cross sections.

Contribution

It develops a unified framework based on factorised virtual corrections, gauge-invariant matrix elements, and differential jet functions for infrared subtraction at all perturbative orders.

Findings

Reproduces known NLO and NNLO results

Simplifies the organisation of subtraction procedures

Facilitates the development of higher-order computational algorithms

Abstract

We provide a general method to construct local infrared subtraction counterterms for unresolved radiative contributions to differential cross sections, to any order in perturbation theory. We start from the factorised structure of virtual corrections to scattering amplitudes, where soft and collinear divergences are organised in gauge-invariant matrix elements of fields and Wilson lines, and we define radiative eikonal form factors and jet functions which are fully differential in the radiation phase space, and can be shown to cancel virtual poles upon integration by using completeness relations and general theorems on the cancellation of infrared singularities. Our method reproduces known results at NLO and NNLO, and yields substantial simplifications in the organisation of the subtraction procedure, which will help in the construction of efficient subtraction algorithms at higher orders.