Single- and double-unresolved limits of polarized tree-level matrix elements

TL;DR

This paper derives the complete set of splitting amplitudes for polarized tree-level QCD matrix elements at NNLO, enabling more precise calculations of polarized collider processes involving unresolved partons.

Contribution

It provides the first analytic derivation of polarized splitting amplitudes at NNLO, extending unpolarized results to include polarization effects in the Larin gamma_5 scheme.

Findings

Derived polarized splitting amplitudes from DIS-like processes

Verified amplitudes in higher multiplicity matrix elements

Facilitates NNLO calculations of polarized spin asymmetries

Abstract

The calculation of exclusive cross sections at next-to-next-to-leading order (NNLO) in QCD requires an analytic understanding of the infrared singular structure with up to two unresolved partons. This has so far only been achieved for unpolarized matrix elements. We derive the full set of splitting amplitudes arising in longitudinally polarized tree-level QCD matrix elements at NNLO in the Larin $\gamma_5$ scheme. They are extracted from DIS-like processes, and are verified in matrix elements of higher multiplicity. Our results will enable the calculation of NNLO corrections to longitudinal spin asymmetries in polarized collider processes.