Quasi-Classical Evaluation of Gluon Saturation Induced Helicity Effects

TL;DR

This paper investigates how gluon saturation effects induce helicity-dependent phenomena in high-energy QCD, revealing a two-particle correlation mechanism that impacts dijet production in polarized electron-nucleus collisions.

Contribution

It introduces a novel saturation-induced helicity effect derived via classical Yang-Mills equations and diagrammatic methods, highlighting its multi-particle correlation nature.

Findings

Saturation effects suppress back-to-back dijet correlations.

The helicity effect magnitude is comparable to direct helicity effects.

The study offers a new way to probe gluon saturation in polarized collisions.

Abstract

At sub-eikonal order in the high-energy limit, helicity dependences are generally contained in the transverse components of the gluon field. In the gluon saturation regime, novel helicity effects arise from the nonlinear interaction between the eikonal-order longitudinal gluon field and the sub-eikonal-order transverse gluon field. We derive this saturation induced helicity-dependent field both by solving the classical Yang-Mills equations and through direct diagrammatic calculations. Our analysis shows that the saturation induced helicity effect is intrinsically a two-particle (or multi-particle) correlation effect, rather than a single-particle distribution effect. Furthermore, we evaluate this effect in the context of double-spin asymmetry for incoherent diffractive dijet production in longitudinally polarized electron-nucleus collisions, using a simplified helicity-extended McLerran-Venugopalan model. We find that the saturation induced helicity effect further suppresses the back-to-back peak in the dijet azimuthal angle correlation, with a magnitude comparable to that of the direct helicity effect. This gluon saturation induced helicity effect may offer a novel avenue to probe gluon saturation in polarized collisions.