Gluon Spin in a Quark Model
  We compute the gluon polarization $\Delta G$ and the gluon total angular momentum $J_g$ in the Isgur-Karl quark model. Taking into account self-interaction contributions, we obtain for both quantities a positive value of about 0.24 at the model scale $\mu_0^2 \simeq 0.25$ GeV$^2$. This estimate is reasonably close to the expectation from polarized deep inelastic scattering analyses. 
V.Barone, T.Calarco and A.Drago