Next-to-soft radiation from a different angle

TL;DR

This paper investigates a formula for leading next-to-soft QCD radiation in collider processes, demonstrating its validity in W+jet production with massive particles and analyzing how it affects angular ordering.

Contribution

It introduces and validates a momentum-shift formula for next-to-soft radiation, expanding understanding of soft-collinear factorization in complex collider processes.

Findings

The formula holds for processes with massive final-state particles.

Momentum shifts disrupt angular ordering of soft radiation.

Provides a physical interpretation of the momentum shift mechanism.

Abstract

Soft and collinear radiation in collider processes can be described in a universal way, that is independent of the underlying process. Recent years have seen a number of approaches for probing whether radiation beyond the leading soft approximation can also be systematically classified. In this paper, we study a formula that captures the leading next-to-soft QCD radiation affecting processes with both final- and initial-state partons, by shifting the momenta in the non-radiative squared amplitude. We first examine W+jet production, and show that a previously derived formula of this type indeed holds in the case in which massive colour singlet particles are present in the final state. Next, we develop a physical understanding of the momentum shifts, showing precisely how they disrupt the well-known angular ordering property of leading soft radiation.