Quark Spin and Orbital Angular Momentum in the Baryon

Abstract

The spin and orbital angular momentum carried by different quark flavors in the nucleon are calculated in the SU(3) chiral quark model with symmetry-breaking. The model is extended to all octet and decuplet baryons. In this model, the reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as function of the partition factor $\kappa$ and the chiral splitting probability $a$ is shown. Although the total amount of the quark spin reduction is canceled by the the equal amount increase of the quark orbital angular momentum, the cancellation does not apply to each quark flavor. Especially, the cancellation between the spin and orbital contributions in the baryon magnetic moment is discussed. Comparisons of our results with other models are also shown.