Three quark currents and baryon spin

We show that three-quark axial currents as required by broken SU(6) spin-flavor symmetry reduce the quark spin contribution to proton spin from ${\mathrm{\Sigma }}_p=1$ (one-quark axial current value) to ${\mathrm{\Sigma }}_p=0.41(12)$ consistent with the empirical value ${\mathrm{\Sigma }}_{p,exp}=0.33(08)$. In the case of the ${\mathrm{\Delta }}^{+}(1232)$ baryon, we find that three-quark axial currents increase the one-quark axial current value ${\mathrm{\Sigma }}_{{\mathrm{\Delta }}^{+}}=3$ to ${\mathrm{\Sigma }}_{{\mathrm{\Delta }}^{+}}=3.87(22)$. We also calculate the quark orbital angular momenta $L_u$ and $L_d$ in the proton and ${\mathrm{\Delta }}^{+}$ and interpret our results in terms of the prolate and oblate geometric shapes of these baryons consistent with their intrinsic quadrupole moments.