dorsal/arxiv
View SchemaCurrent Conservation in the Covariant Quark-Diquark Model of the Nucleon
| Authors | Martin Oettel, Mike Pichowsky, Lorenz von Smekal |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9909082 |
| URL | https://arxiv.org/abs/nucl-th/9909082 |
| DOI | 10.1007/s100530050034 |
| Journal | Eur.Phys.J. A8 (2000) 251-281 |
Abstract
The description of baryons as fully relativistic bound states of quark and glue reduces to an effective Bethe-Salpeter equation with quark-exchange interaction when irreducible 3-quark interactions are neglected and separable 2-quark (diquark) correlations are assumed. This covariant quark-diquark model of baryons is studied with the inclusion of the quark substructure of the diquark correlations. In order to maintain electromagnetic current conservation it is then necessary to go beyond the impulse approximation. A conserved current is obtained by including the coupling of the photon to the exchanged quark and direct ``seagull'' couplings to the diquark structure. Adopting a simple dynamical model of constituent quarks and exploring various parametrisations of scalar diquark correlations, the nucleon Bethe-Salpeter equation is solved and the proton and neutron electromagnetic form factors are calculated numerically. The resulting magnetic moments are still about 50% too small, the improvements necessary to remedy this are discussed. The results obtained in this framework provide an excellent description of the electric form factors (and charge radii) of the proton, up to a photon momentum transfer of 3.5GeV^2, and the neutron.
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"abstract": "The description of baryons as fully relativistic bound states of quark and\nglue reduces to an effective Bethe-Salpeter equation with quark-exchange\ninteraction when irreducible 3-quark interactions are neglected and separable\n2-quark (diquark) correlations are assumed. This covariant quark-diquark model\nof baryons is studied with the inclusion of the quark substructure of the\ndiquark correlations. In order to maintain electromagnetic current conservation\nit is then necessary to go beyond the impulse approximation. A conserved\ncurrent is obtained by including the coupling of the photon to the exchanged\nquark and direct ``seagull\u0027\u0027 couplings to the diquark structure. Adopting a\nsimple dynamical model of constituent quarks and exploring various\nparametrisations of scalar diquark correlations, the nucleon Bethe-Salpeter\nequation is solved and the proton and neutron electromagnetic form factors are\ncalculated numerically. The resulting magnetic moments are still about 50% too\nsmall, the improvements necessary to remedy this are discussed. The results\nobtained in this framework provide an excellent description of the electric\nform factors (and charge radii) of the proton, up to a photon momentum transfer\nof 3.5GeV^2, and the neutron.",
"arxiv_id": "nucl-th/9909082",
"authors": [
"Martin Oettel",
"Mike Pichowsky",
"Lorenz von Smekal"
],
"categories": [
"nucl-th",
"hep-ph"
],
"doi": "10.1007/s100530050034",
"journal_ref": "Eur.Phys.J. A8 (2000) 251-281",
"title": "Current Conservation in the Covariant Quark-Diquark Model of the Nucleon",
"url": "https://arxiv.org/abs/nucl-th/9909082"
},
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