Proper identification of the gluon spin

Properties of the recently proposed gauge-invariant gluon spin Sg are studied and compared to the usually defined “gluon polarization” Δg. By explicit 1-loop calculations in a quark state, it is found that Sg=59Δg. Furthermore, 45 of Sg can actually be identified as a “static-field” contribution and shown to cancel exactly an analogous static term in the gluon orbital angular momentum Lg, leaving Sg+Lg unaltered. These observations suggest that by an alternative definition, the gluon contribution to the nucleon spin may be drastically smaller than in the conventional wisdom.