Proper identification of the gluon spin

Abstract

Properties of the recently proposed gauge-invariant gluon spin $S_g$ are studied and compared to the usually defined "gluon polarization" $\Delta g$. By explicit 1-loop calculations in a quark state, it is found that $S_g=\frac{5}{9}\Delta g$. Furthermore, $\frac{4}{5}$ of $S_g$ can actually be identified as a "static-field" contribution and shown to cancel exactly an analogous static term in the gluon orbital angular momentum $L_g$, leaving $S_g+L_g$ unaltered. These observations suggest that if properly identified, the gluon contribution to the nucleon spin may be drastically smaller than in the conventional wisdom.

9 pages, no figure; minor editing revision, references updated

References in corpus (5)

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• Spin and orbital angular momentum in gauge theories: Nucleon spin structure and multipole radiation revisited
• Do gluons carry half of the nucleon momentum?
• Gauge- and frame-independent decomposition of nucleon spin
• Physical decomposition of the gauge and gravitational fields