Transverse Spin in QCD: Radiative Corrections

TL;DR

This paper investigates the properties and renormalization of transverse spin operators in light-front QCD, revealing their interaction dependence, a novel decomposition, and the dominant intrinsic fermion contribution after one-loop corrections.

Contribution

It provides the first detailed analysis of the interaction-dependent transverse spin operator, including its decomposition, physical relevance, and one-loop renormalization in light-front QCD.

Findings

Transverse spin operators are interaction dependent in light-front QCD.

A meaningful decomposition of the transverse spin operator exists.

The intrinsic fermion part dominates the transverse spin after renormalization.

Abstract

In this paper we address various issues connected with transverse spin in light front QCD. The transverse spin operators, in $A^+ = 0$ gauge, expressed in terms of the dynamical variables are explicitly interaction dependent unlike the helicity operator which is interaction independent in the topologically trivial sector of light-front QCD. Although it cannot be separated into an orbital and a spin part, we have shown that there exists an interesting decomposition of the transverse spin operator. We discuss the physical relevance of such a decomposition. We perform a one loop renormalization of the full transverse spin operator in light-front Hamiltonian perturbation theory for a dressed quark state. We explicitly show that all the terms dependent on the center of mass momenta get canceled in the matrix element. The entire non-vanishing contribution comes from the fermion intrinsic -like part of the transverse spin operator as a result of cancellation between the gluonic intrinsic-like and the orbital-like part of the transverse spin operator. We compare and contrast the calculations of transverse spin and helicity of a dressed quark in perturbation theory.