Combined effects of internal quark motion and SU(6) breaking on the properties of the baryon ground state

Journal Article · Tue Feb 01 04:00:00 EST 1977 · Phys. Rev., D; (United States)

DOI:https://doi.org/10.1103/PhysRevD.15.844· OSTI ID:7228668

Le Yaouanc, A; Oliver, L; Pene, O; Raynal, J C

A sizeable departure from naive SU(6) results has been shown to come, within the quark-model approach, from the relativistic character of the internal quark motion: axial-vector couplings and chiral configuration mixing. On the other hand, an interband mixing (56, 0/sup +/)/sub N /sub 0// + (70, 0/sup +/)/sub N /sub 2// of the harmonic-oscillator levels correctly describes the large-x behavior of the ratio F/sup e n//sub 2//F/sup e p//sub 2/. This paper is devoted to further consequences of both effects which result from their interference. Keeping the same basic parameters already used in the previous calculations, we compute mass differences within the 1/2/sup +/ octet and axial-vector and magnetic couplings. The most striking results are (i) the survival of the good SU(6) predictions: ..mu../sup tot//sub p//..mu../sub n/ approx. = -3/2, (F/D)/sub axialhyphen/ approx. = 2/3; (ii) the explanation in sign and order of magnitude of the ..sigma..-..lambda.. splitting; (iii) the explanation of the sizeable discrepancy between experiment and SU(6) for the various ..delta..-N couplings, which are systematically underestimated: the magnetic dipole transition ..mu..*/..mu../sup tot//sub p/ approx. = (2 ..sqrt..2 /3)(1 + 30%) and the ..delta.. ..-->.. N..pi.. width. The new parameters introduced are the lambda-P quark mass difference (fixed by the (..sigma.. + ..lambda..)/2-N splitting), the anomalous quark magnetic moment kappa (fixed by ..mu../sup tot//sub p/), and (g/sub A/)/sub q/, the renormalized quark axial-vector coupling (fixed by vertical-bar G/sub A//G/sub V/ vertical-bar ). The conclusions are that: in spite of an unwanted problem for the neutron charge form factor: a good description can be obtained for fine details of the baryon ground state, and that, as suspected, the quarks must be given a structure.

• Research Organization: Laboratoire de Physique Theorique et Hautes Energies, Orsay, France
• OSTI ID: 7228668
• Journal Information: Phys. Rev., D; (United States), Journal Name: Phys. Rev., D; (United States) Vol. 15:3; ISSN PRVDA
• Country of Publication: United States
• Language: English

Related Subjects

645303* -- High Energy Physics-- Particle Invariance Principles & Symmetries-- Applications to Strong Interactions-- (-1987)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BARYONS
CHIRAL SYMMETRY
COMPOSITE MODELS
COUPLING
ELEMENTARY PARTICLES
ENERGY LEVELS
FERMIONS
FIELD THEORIES
GENERAL RELATIVITY THEORY
GROUND STATES
HADRONS
LIE GROUPS
MAGNETIC MOMENTS
MASS DIFFERENCE
MATHEMATICAL MODELS
PARTICLE MODELS
PARTICLE PROPERTIES
PARTICLE STRUCTURE
POSTULATED PARTICLES
QUARK MODEL
QUARKS
RELATIVITY THEORY
SU GROUPS
SU-6 GROUPS
SYMMETRY
SYMMETRY BREAKING
SYMMETRY GROUPS