85 research outputs found
Extended Goldstone-Boson-Exchange Constituent Quark Model
We present an extension of the Goldstone-boson-exchange constituent quark
model including additional interactions beyond the ones used hitherto. For the
hyperfine interaction between the constituent quarks we assume pseudoscalar,
vector, and scalar meson exchanges and consider all relevant force components
produced by these types of exchanges. The resulting model, which corresponds to
a relativistic Poincare-invariant Hamiltonian (or equivalently mass operator),
provides a unified framework for a covariant description of all light and
strange baryons. The ground states and resonances up to an excitation energy of
about 2 GeV are reproduced in fair agreement with phenomenology, with the
exception of the first excitations above the Lambda and Xi ground states.Comment: 11 pages, 4 figures, 3 tables; substantial revisions, additional
author, bibliography extended and update
Strong Decays of N and Delta Resonances in the Point-Form Formalism
We present covariant predictions of relativistic constituent quark models for
pi and eta decay widths of N and Delta resonances. The results are calculated
for a model decay operator within the point-form spectator approximation. It is
found that most theoretical values underestimate the experimental data
considerably.Comment: 4 pages; Proceedings for N*2004, Grenoble, March 24-27 (2004
Nucleon magnetic moments in an extended chiral constituent quark model
We present results for the nucleon magnetic moments in the context of an
extended chiral constituent quark model based on the mechanism of the Goldstone
boson exchange, as suggested by the spontaneous breaking of chiral symmetry in
QCD. The electromagnetic charge-current operator is consistently deduced from
the model Hamiltonian, which includes all force components for the
pseudoscalar, vector and scalar meson exchanges. Thus, the continuity equation
is satisfied for each piece of the interaction, avoiding the introduction of
any further parameter. A good agreement with experimental values is found. The
role of isoscalar two-body operators, not constrained by the continuity
equation, is also investigated.Comment: 7 pages, 1 table, submitted for publication to Phys. Lett. B,
elsart.sty/elsart12.sty include
Hadronic Decays of N and \Delta Resonances in a Chiral Quark Model
\pi and \eta decay modes of light baryon resonances are investigated within a
chiral quark model whose hyperfine interaction is based on Goldstone-boson
exchange. For the decay mechanism a modified version of the 3P0 model is
employed. Our primary aim is to provide a further test of the recently proposed
Goldstone-boson-exchange constituent quark model. We compare the predictions
for \pi and \eta decay widths with experiment and also with results from a
traditional one-gluon-exchange constituent quark model. The differences between
nonrelativistic and semirelativistic versions of the constituent quark models
are outlined. We also discuss the sensitivity of the results on the
parametrization of the meson wave function entering the 3P0 model.Comment: 17 pages, 6 eps figure
Chiral symmetry patterns of excited mesons with the Coulomb-like linear confinement
The spectrum of mesons in a model where the only interaction is a
linear Coulomb-like instantaneous confining potential is studied. The
single-quark Green function as well as the dynamical chiral symmetry breaking
are obtained from the Schwinger-Dyson (gap) equation. Given the dressed quark
propagator, a complete spectrum of "usual" mesons is obtained from the
Bethe-Salpeter equation. The spectrum exhibits restoration of chiral and
symmetries at large spins and/or radial excitations. This property is
demonstrated both analytically and numerically. At large spins and/or radial
excitations higher degree of degeneracy is observed, namely all states with the
given spin fall into reducible representations that combine all possible chiral multiplets with the
given and . The structure of the meson wave functions as well as the
form of the angular and radial Regge trajectories are investigated.Comment: 1. Order of references has been changed and one reference has been
added; 2. A short discussion of nonrelativistic and semirelativistic quark
models has been added in the conclusion part on referee's request. To appear
in Phys. Rev.
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