Implications of Color Gauge Symmetry For Nucleon Spin Structure

Abstract

We study the chromodynamical gauge symmetry in relation to the internal spin structure of the nucleon. We show that 1) even in the helicity eigenstates the gauge-dependent spin and orbital angular momentum operators do not have gauge-independent matrix element; 2) the evolution equations for the gluon spin take very different forms in the Feynman and axial gauges, but yield the same leading behavior in the asymptotic limit; 3) the complete evolution of the gauge-dependent orbital angular momenta appears intractable in the light-cone gauge. We define a new gluon orbital angular momentum distribution $L_g(x)$ which {\it is} an experimental observable and has a simple scale evolution. However, its physical interpretation makes sense only in the light-cone gauge just like the gluon helicity distribution $\Delta g(x)$y.

Minor corrections are made in the text

References in corpus (5)

• Quark and Gluon Orbital Angular Momentum and Spin in Hard Processes
• Quark Orbital-Angular-Momentum Distribution in the Nucleon
• Evolution Equations for Higher Moments of Angular Momentum Distributions
• How Much of the Nucleon Spin is Carried by Glue?
• Gluon Spin in a Quark Model

Cited by in corpus (26)

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• The Gauge-Invariant Angular Momentum Sum-Rule for the Proton
• Proper identification of the gluon spin
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• Does the Gluon Spin Contribute in A Gauge Invariant Way to Nucleon Spin?
• QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part
• Exploring the polarization of gluons in the nucleon
• Proton spin after 30 years: what we know and what we don't?
• Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena
• Orbital Angular Momentum Parton Distributions in Light-Front Dynamics
• The proton spin decomposition : path dependence and gauge symmetry