Three quark currents and baryon spin

TL;DR

This paper demonstrates that incorporating three-quark axial currents, due to broken SU(6) symmetry, significantly alters the quark spin contributions to baryons, aligning theoretical predictions with experimental data and revealing geometric shapes of baryons.

Contribution

It introduces the role of three-quark axial currents in baryon spin structure, improving agreement with empirical data and providing geometric interpretations.

Findings

Reduces proton spin contribution from 1 to approximately 0.41.

Increases $elta^+$ axial current value from 3 to about 3.87.

Predicts prolate and oblate shapes for proton and $elta^+$ baryons.

Abstract

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 $\Sigma_p = 1$ (one-quark axial current value) to $\Sigma_p = 0.41(12)$ consistent with the empirical value $\Sigma_{p, exp} = 0.33(08)$. In the case of the $\Delta^+(1232)$ baryon, we find that three-quark axial currents increase the one-quark axial current value $\Sigma_{\Delta^+} = 3$ to $\Sigma_{\Delta^+} = 3.87(22)$. We also calculate the quark orbital angular momenta $L_u$ and $L_d$ in the proton and $\Delta^+$ and interpret our results in terms of the prolate and oblate geometric shapes of these baryons consistent with their intrinsic quadrupole moments.