1,046 research outputs found
The Nucleon-Nucleon Potential in the Chromo-Dielectric Soliton Model: Statics
We study the N-N interaction in the framework of the chromo-dielectric
soliton model. Here, the long-range parts of the nonabelian gluon
self-interactions are assumed to give rise to a color-dielectric function which
is parameterized in terms of an effective scalar background field. The
six-quark system is confined in a deformed mean field through an effective
non-linear interaction between the quarks and the scalar field. The CDM is
covariant, respects chiral invariance, leads to absolute color confinement and
is free of the spurious long range Van der Waals forces which trouble
non-relativistic investigations employing a confining potential. Six-quark
molecular-type configurations are generated as a function of deformation and
their energies are evaluated in a coupled channel analysis. By using molecular
states instead of cluster model wave functions, all important six-quark
configurations are properly taken into account. The corresponding Hamiltonian
includes the effective interaction between the quarks and the scalar background
field and quark-quark interactions generated through one gluon exchange treated
in Coulomb gauge. When evaluating the gluonic propagators, the inhomogeneity
and deformation of the dielectric medium are taken into account. Results for
the adiabatic nucleon-nucleon potential are presented, and the various
contributions are discussed. Finally, an outlook is given on how, in the next
stage of our investigation, the dynamical effects will be incorporated by
employing the generator coordinate method.Comment: 43 pages, REVTeX file followed by 11 uuencoded PostScript figures,
DOE/ER/40427-02-N9
Multiquark Systems in a Constituent Quark Model with Chiral Dynamics
We discuss the stability of multiquark systems within the recent model of
Glozman et al. where the chromomagnetic hyperfine interaction is replaced by
pseudoscalar-meson exchange. We find that such an interaction binds a heavy
tetraquark system ( and by GeV.
This is at variance with results of previous models where is
unstable.Comment: 6 pages, Plain Latex, Contribution to the Workshop''Quark Confinement
and the Hadron Spectrum II'', Como, Italy, June 26--29, 1996, to appear in
the Proceedings, ed. Nora Brambilla, World Scientifi
Quasi-Two-Body Decays of Nonstrange Baryons
We examine the decays of nonstrange baryons to the final states ,
, , , , , and
, in a relativized pair-creation() model which has
been developed in a previous study of the decays of the same baryon
states. As it is our goal to provide a guide for the possible discovery of new
baryon states at CEBAF and elsewhere, we examine the decays of resonances which
have already been seen in the partial-wave analyses, along with those of states
which are predicted by the quark model but which remain undiscovered. The level
of agreement between our calculation and the available widths from the
partial-wave analyses is encouraging.Comment: 41 pages, CEBAF-TH-93-1
Heavy-Flavour Pentaquarks in a Chiral Constituent Quark Model
Within the chiral constituent quark model of Glozman and Riska, we discuss
the stability of heavy pentaquarks, i.e. hadrons containing four light quarks
and a heavy antiquark. The spin-dependent part of the Hamiltonian is dominated
by the short-range part of the Goldstone-boson-exchange interaction. We find
that these systems are not bound, having an energy above the lowest
dissociation threshold into a baryon and a meson.Comment: 10 pages + table
On a three-body confinement force in hadron spectroscopy
Recently it has been argued that a three-body colour confinement interaction
can affect the stability condition of a three-quark system and the spectrum of
a tetraquark described by any constituent quark model. Here we discuss the role
of a three-body colour confinement interaction in a simple quark model and
present some of its implications for the spectra of baryons, tetraquarks and
six-quark systems.Comment: 19 pages (RevTeX), addition of new material regarding the NN
interaction, more accurate discussion of the baryonic case, accepted for
publication in Phys. Rev.
New approach to He charge distribution
We present a study of the He charge distribution based on realistic
nucleonic wave functions and incorporation of the nucleon's quark substructure.
The central depression of the proton point density seen in modern four-body
calculations is too small by itself to lead to a correct description of the
charge distribution. We utilize six-quark structures calculated in the
Chromodielectric Model for N-N interactions, and we find a swelling of the
proton charge distribution as the internucleon distance decreases. These charge
distributions are combined with the He wave function using the Independent
Pair Approximation and two-body distributions generated from Green's Function
Monte Carlo calculations. We obtain a reasonably good fit to the experimental
charge distribution without including meson exchange currents.Comment: 9 pages, LaTeX, 4 figures (Figures 1 and 2 doesn't exist as
postscript files : they are only available on request
The Application of the Econometric Models with Qualitative Variables in the Analysis of the Non Academic Behaviors at the Level of the Romanian Higher Education System
The purpose of this paper was to apply the econometric models with qualitative variables in order to analyze two non academic behaviors at the level of the Romanian higher education system: cheating on the exams by copying or by direct or intermediary intervention at the professor.Logit Model, survey, sample, fraud
New Baryons in the Delta eta and Delta omega Channels
The decays of excited nonstrange baryons into the final states Delta eta and
Delta omega are examined in a relativized quark pair creation model. The
wavefunctions and parameters of the model are fixed by previous calculations of
N pi and N pi pi, etc., decays through various quasi-two body channels
including N eta and N omega. Our results show that the combination of
thresholds just below the region of interest and the isospin selectivity of
these channels should allow the discovery of several new baryons in such
experiments.Comment: 10 pages, RevTe
Strange Decays of Nonstrange Baryons
The strong decays of excited nonstrange baryons into the final states Lambda
K, Sigma K, and for the first time into Lambda(1405) K, Lambda(1520) K,
Sigma(1385) K, Lambda K*, and Sigma K*, are examined in a relativized quark
pair creation model. The wave functions and parameters of the model are fixed
by previous calculations of N pi and N pi pi, etc., decays. Our results show
that it should be possible to discover several new negative parity excited
baryons and confirm the discovery of several others by analyzing these final
states in kaon production experiments. We also establish clear predictions for
the relative strengths of certain states to decay to Lambda(1405) K and
Lambda(1520) K, which can be tested to determine if a three-quark model of the
Lambda(1405) K is valid. Our results compare favorably with the results of
partial wave analyses of the limited existing data for the Lambda K and Sigma K
channels. We do not find large Sigma K decay amplitudes for a substantial group
of predicted and weakly established negative-parity states, in contrast to the
only previous work to consider decays of these states into the strange final
states Lambda K and Sigma K.Comment: 25 pages, 8 figures, RevTe
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