Nucleon Spin in QCD: Old Crisis and New Resolution

Abstract

We discuss the shortfalls of existing resolutions of the long-standing gauge invariance problem of the canonical decomposition of the nucleon spin to the spin and angular momentum of quarks and gluons. We provide two logically flawless expressions of nucleon spin which have different physical meanings, using the gauge independent Abelian decomposition. The first one is based on the assumption that all gluons (binding and valence gluons) contribute to the nucleon spin, but the second one is based on the assumption that only the binding gluons (and the quarks) contribute to it. We propose the second expression to be the physically correct one.

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Cited by in corpus (11)

• The angular momentum controversy: What's it all about and does it matter?
• Notes on the orbital angular momentum of quarks in the nucleon
• Is gauge-invariant complete decomposition of the nucleon spin possible ?
• Geometrical approach to the proton spin decomposition
• Gluon polarization in the nucleon demystified
• Quark tensor charge and electric dipole moment within the Schwinger-Dyson formalism
• Are there infinitely many decompositions of the nucleon spin ?
• Cho-Duan-Ge decomposition of QCD in the constraintless Clairaut-type formalism
• Quark and Glue Components of the Proton Spin from Lattice Calculation
• Gauge invariant gluon spin operator for spinless non-linear wave solutions
• Consistent gauge invariant nucleon spin decomposition