Nucleon properties in the covariant quark-diquark model |
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Authors: | M Oettel R Alkofer L von Smekal |
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Institution: | 1. Institut für Theoretische Physik, Universit?t Tübingen, Auf der Morgenstelle 14, 72076, Tübingen, Germany 2. Institut für Theoretische Physik III, Universit?t Erlangen-Nürnberg, Staudtstr. 7, 91058, Erlangen, Germany
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Abstract: | In the covariant quark-diquark model the effective Bethe-Salpeter (BS) equations for the nucleon and the Δ are solved including
scalar and axial vector diquark correlations. Their quark substructure is effectively taken into account in both, the interaction kernel of the BS
equations and the currents employed to calculate nucleon observables. Electromagnetic current conservation is maintained.
The electric form factors of proton and neutron match the data. Their magnetic moments improve considerably by including axial
vector diquarks and photon induced scalar-axial vector transitions. The isoscalar magnetic moment can be reproduced, the isovector
contribution is about 15% too small. The ratio μG
E/G
M and the axial and strong couplings g
A, g
NN, provide an upper bound on the relative importance of axial vector diquarks confirming that scalar diquarks nevertheless
describe the dominant 2-quark correlations inside nucleons.
Received: 3 July 2000 / Accepted: 15 August 2000 |
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Keywords: | PACS 11 10 St Bound states Bethe-Salpeter equations – 12 40 Yx Hadron mass models and calculations – 13 40 Gp Electromagnetic form factors – 14 20 Dh Protons and neutrons |
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