Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
1996-10-21
Nucl.Phys. A627 (1997) 427-459
Physics
High Energy Physics
High Energy Physics - Phenomenology
33 pages, Latex, 9 Postscpript figures, section on the excited states has been completely rewritten after error was detected,
Scientific paper
10.1016/S0375-9474(97)00402-8
The tensor-RPA approach developed previously in part I is applied to the Nambu-Jona-Lasinio (NJL) model. As a first step we investigate the structure of Dirac-Hartree-Fock solutions for a rotationally and isospin invariant ground-state density. Whereas vacuum properties can be reproduced, no solitonic configuration for a system with unit baryon number is found. We then solve the tensor-RPA equation employing simple models of the nucleon ground state. In general the ph interaction effects a decrease of the excited states to lower energies. Due to an enhanced level density at low energies the obtained spectra cannot be matched with the experimental data when a standard MIT-bag configuration is used. However, when the size of the nucleon quark core is reduced to approximately 0.3 fm a fair description of the baryon spectrum in the positive-parity channel is achieved. For this purpose the residual interaction turns out to be crucial and leads to a significant improvement compared with the mean-field spectra.
Geiss Johannes
Hardt Steffen
Lenske Horst
Mosel Ulrich
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