Gluon polarization in the nucleon demystified

TL;DR

This paper introduces a simplified scheme for decomposing nucleon spin, demonstrating that the gluon helicity derived from their method aligns with the measurable polarized gluon distribution, thus clarifying gluon contributions to nucleon spin.

Contribution

The paper proposes a straightforward separation scheme for gauge fields that yields a gauge-invariant gluon helicity consistent with experimental measurements.

Findings

Gluon helicity matches the first moment of the polarized gluon distribution.

The separation scheme simplifies the gauge-invariant decomposition of nucleon spin.

The approach aligns theoretical definitions with experimental observables.

Abstract

Recently, X. Chen et al. proposed a new approach to the gauge invariant decomposition of the nucleon spin into helicity and orbital parts. The key ingredient in their construction is the separation of the gauge field into `physical' and `pure gauge' parts. We suggest a simple separation scheme and show that the resulting gluon helicity coincides with the first moment of the conventional polarized gluon distribution measurable in high energy experiments.