The Unresolved Behaviour of Polarized Scattering Matrix Elements at NNLO in QCD

TL;DR

This paper investigates the complex behavior of polarized scattering matrix elements at NNLO in QCD, providing insights crucial for precise spin asymmetry measurements in polarized hadron collisions.

Contribution

It derives the universal infrared behavior of polarized real radiation matrix elements at NNLO, facilitating the development of subtraction schemes for polarized cross sections.

Findings

Universal infrared limits for polarized matrix elements derived

Enables construction of NNLO subtraction schemes for polarized processes

Improves precision in spin asymmetry calculations

Abstract

Spin asymmetries in collisions of spin-polarized hadrons probe polarized parton distributions, which encode the spin structure of the colliding hadrons. To perform precision physics studies with spin asymmetries, higher order QCD corrections to the underlying polarized cross sections are required. Their numerical implementation relies on the use of an infrared subtraction scheme, which extracts the infrared singular pieces from the real and virtual subprocesses. We derive the universal behaviour of longitudinally polarized real radiation matrix elements in their infrared-singular limits up to next-to-next-to-leading order (NNLO) in QCD, thereby enabling the construction of infrared subtraction schemes for generic polarized cross sections at NNLO.