On the Subleading-Soft Behaviour of QCD Amplitudes

TL;DR

This paper investigates the sub-leading soft gluon emission in QCD amplitudes, revealing that it is governed by universal differential operators derived from on-shell recursion and gauge invariance.

Contribution

It demonstrates that the sub-leading soft term in QCD can be universally described by differential operators, extending previous results from gravity and gluon scattering.

Findings

Sub-leading soft gluon behavior is controlled by universal differential operators.

The form of these operators can be derived from on-shell recursion relations.

Gauge invariance underpins the universality of the sub-leading soft terms.

Abstract

We elaborate on the radiative behaviour of tree-level scattering amplitudes in the soft regime. We show that the sub-leading soft term in single-gluon emission of quark-gluon amplitudes in QCD is controlled by differential operators, whose universal form can be derived from both on-shell recursion relation and gauge invariance, as it was shown to hold for graviton- and gluon-scattering.