Eur. Phys. J. A 10, 395-446
The light-baryon spectrum in a relativistic quark model with instanton-induced quark forces
The non-strange-baryon spectrum and ground states
U. Löring, B.Ch. Metsch and H.R. PetryInstitut für Theoretische Kernphysik, Universität Bonn, Nußallee 14-16, D-53115 Bonn, Germany loering@itkp.uni-bonn.de
(Received: 27 March 2001 Communicated by V.V. Anisovich )
Abstract
This is the second of a series of three papers treating light-baryon
resonances up to 3 GeV within a relativistically covariant quark model based
on the three-fermion Bethe-Salpeter equation with instantaneous two- and
three-body forces. In this paper we apply the covariant Salpeter framework
(which we developed in the first paper, U. Löring, K. Kretzschmar, B.Ch. Metsch, H.R. Petry,
Eur. Phys. J. A 10, 309 (2001))
to specific quark
model calculations. Quark confinement is realized by a linearly rising
three-body string potential with appropriate spinorial structures in
Dirac space. To describe the hyperfine structure of the baryon spectrum we
adopt 't Hooft's residual interaction based on QCD-instanton effects and
demonstrate that the alternative one-gluon exchange is disfavored on
phenomenological grounds. Our fully relativistic framework allows to
investigate the effects of the full Dirac structures of residual and
confinement forces on the structure of the mass spectrum. In the present
paper we present a detailed analysis of the complete non-strange-baryon
spectrum and show that several prominent features of the nucleon spectrum
such as, e.g., the Roper resonance and approximate "parity doublets"
can be uniformly explained due to a specific interplay of relativistic
effects, the confinement potential and 't Hooft's force. The results for the
spectrum of strange baryons will be discussed in a subsequent paper, see
U. Löring, B.Ch. Metsch, H.R. Petry,
this issue, p. 447.
11.10.St - Bound and unstable states; Bethe-Salpeter equations.
12.39.Ki - Relativistic quark model.
12.40.Yx - Hadron mass models and calculations.
14.20.-c - Baryons (including antiparticles).
© Società Italiana di Fisica, Springer-Verlag 2001
