title: Octet spin fractions and the proton spin problem.
abstract: The relatively small fraction of the spin of the proton carried by its quarks presents a major challenge to our understanding of the strong interaction. Traditional efforts to explore this problem have involved new and imaginative experiments and QCD based studies of the nucleon. We propose a new approach to the problem that exploits recent advances in lattice QCD. In particular, we extract values for the spin carried by the quarks in other members of the baryon octet in order to see whether the suppression observed for the proton is a general property or depends significantly on the baryon structure. We compare these results with the values for the spin fractions calculated within a model that includes the effects of confinement, relativity, gluon exchange currents, and the meson cloud required by chiral symmetry, finding a very satisfactory level of agreement given the precision currently attainable.
authors.affiliation: CSSM and ARC Centre of Excellence for Particle Physics at the Tera-scale, School of Chemistry and Physics, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: P E
authors.initials: PE
authors.lastname: Shanahan
authors.affiliation: CSSM and ARC Centre of Excellence for Particle Physics at the Tera-scale, School of Chemistry and Physics, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: A W
authors.initials: AW
authors.lastname: Thomas
authors.affiliation: CSSM and ARC Centre of Excellence for Particle Physics at the Tera-scale, School of Chemistry and Physics, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Tsushima
authors.affiliation: CSSM and ARC Centre of Excellence for Particle Physics at the Tera-scale, School of Chemistry and Physics, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: R D
authors.initials: RD
authors.lastname: Young
authors.affiliation: Department of Physics, University of South Carolina, Columbia, South Carolina, USA.
authors.forename: F
authors.initials: F
authors.lastname: Myhrer