204 research outputs found
Narrow Pentaquark States in a Quark Model with Antisymmetrized Molecular Dynamics
The exotic baryon is studied with microscopic
calculations in a quark model by using a method of antisymmetrized molecular
dynamics(AMD). We predict narrow states, ,
, and , which nearly degenerate in a
low-energy region of the system. We discuss decay widths and
estimate them to be for the , and
MeV for the state.Comment: Talk given at International Workshop on PENTAQUARK04, Spring-8,
Hyogo, Japan, 20-23 Jul 200
Axial vector tetraquark with S=+2
Possibility of an axial vector isoscalar tetraquark with
is discussed. If the pentaquark has the
configuration, the isoscalar
(-meson) state with is expected to
exist in the mass region lower than or close to the mass of .
Within a flux-tube quark model, a possible resonant state of
is suggested to appear around 1.4 GeV with the
width MeV. We propose that the -meson is a
good candidate for the tetraquark search, which would be observed in the
decay channel.Comment: 20 pages, 5 figures, submitted to Phys.Rev.
Model-independent study of the QCD sum rule for the pi NN coupling constant
We reinvestigate the QCD sum rule for the pi NN coupling constant, g,
starting from the vacuum-to-pion matrix element of the correlation function of
the interpolating fields of two nucleons. We study in detail the physical
content of the correlation function without referring to the effective theory.
We consider the invariant correlation functions by splitting the correlation
function into different Dirac structures. We show that the coefficients of the
double-pole terms are proportional to g but that the coefficients of the
single-pole terms are not determined by g. In the chiral limit the single-pole
terms as well as the continuum terms are ill defined in the dispersion
integral. Therefore, the use of naive QCD sum rules obtained from the invariant
correlation functions is not justified. A possible procedure to avoid this
difficulty is discussed.Comment: 20 pages, 2 figure
Single-Particle Spin-Orbit Strengths of the Nucleon and Hyperons by SU6 Quark-Model
The quark-model hyperon-nucleon interaction suggests an important
antisymmetric spin-orbit component. It is generated from a color analogue of
the Fermi-Breit interaction dominating in the one-gluon exchange process
between quarks. We discuss the strength S_B of the single-particle spin-orbit
potential, following the Scheerbaum's prescription. Using the SU6 quark-model
baryon-baryon interaction which was recently developed by the Kyoto-Niigata
group, we calculate NN, Lambda N and Sigma N G-matrices in symmetric nuclear
matter and apply them to estimate the strength S_B. The ratio of S_B to the
nucleon strength S_N =~ -40 MeV*fm^5 is (S_Lambda)/(S_N) =~ 1/5 and
(S_Sigma)/(S_N) =~ 1/2 in the Born approximation. The G-matrix calculation of
the model FSS modifies S_Lambda to (S_Lambda)/(S_N) =~ 1/12. For S_N and
S_Sigma, the effect of the short-range correlation is comparatively weak
against meson-exchange potentials with a short-range repulsive core. The
significant reduction of the Lambda single-particle potential arises from the
combined effect of the antisymmetric LS force, the flavor-symmetry breaking
originating from the strange to up-down quark-mass difference, as well as the
effect of the short-range correlation. The density dependence of S_B is also
examined.Comment: 26 page
eta-Nucleus interactions and in-medium properties of N*(1535) in chiral models
The properties of eta-nucleus interaction and their experimental consequences
are investigated with eta-nucleus optical potentials obtained by postulating
the N*(1535) dominance for eta-N system. The N*(1535) properties in nuclear
medium are evaluated by two kinds of chiral effective models based on distinct
pictures of N*(1535). We find that these two models provide qualitatively
different optical potentials of the eta meson, reflecting the in-medium
properties of N*(1535) in these models. In order to compare these models in
physical observables, we calculate spectra of (d,3He) reactions for the eta
mesic nucleus formation with various kinds of target nuclei. We show that the
(d,3He) spectra obtained in these models are significantly different and are
expected to be distinguishable in experiments.Comment: 24 pages, 8 figure
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