1,023 research outputs found
Two-scale scalar mesons in nuclei
We generalize the linear sigma model in order to develop a chiral-invariant
model of nuclear structure. The model is natural, and contains not only the
usual sigma meson which is the chiral partner of the pion but also a new
chiral-singlet that is responsible for the medium-range nucleon-nucleon
attraction. This approach provides significant advantages in terms of its
description of nuclear matter and finite nuclei in comparison with conventional
models based on the linear sigma model.Comment: 12 pages, including 3 tables and 3 figures; preprint number is adde
A Faddeev Calculation for Pentaquark in Diquark Picture with Nambu-Jona-Lasinio Type Interaction
A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark
in the diquark picture of Jaffe and Wilczek in which is a
diquark-diquark- three-body system.
Nambu-Jona-Lasinio (NJL) model is used to calculate the lowest order diagrams
in the two-body scatterings of and . With the use of coupling
constants determined from the meson sector, we find that
interaction is attractive while interaction is repulsive, and there is no
bound pentaquark state. A bound pentaquark can only be
obtained with unphysically strong vector mesonic coupling constants.Comment: 4 pages, 4 figure
- and -hypernuclei
- and -hypernuclei are studied in the quark-meson
coupling (QMC) model. Comparisons are made with the results for
-hypernuclei studied in the same model previously. Although the scalar
and vector potentials felt by the , and in
the corresponding hypernuclei multiplet which has the same baryon numbers are
quite similar, the wave functions obtained, e.g., for state, are
very different. The baryon density distribution in
Pb is much more pushed away from the center than that for
the in Pb due to the Coulomb force. On the contrary,
the baryon density distributions in -hypernuclei are
much larger near the origin than those for the in the corresponding
-hypernuclei due to its heavy mass. It is also found that level
spacing for the single-particle energies is much smaller than that
for the and .Comment: Latex, 14 pages, 4 figures, text was extended, version to appear in
Phys. Rev.
Dynamical study of mesons
It has been recently conjectured by Selem and Wilczek \cite{Sel06} the
existence of a meson due to strong correlations between
the two light antiquarks. We make a detailed study of this system within a
dynamical quark model which has proven to be successful in reproducing the most
important features of low-energy hadron phenomenology. Our results, obtained
within a parameter-free calculation, show that the antidiquark component of the
system indeed entails the stronger attraction, and drives
its energy much lower than the threshold, but still above the
or thresholds. We have also studied the
and systems. Exotic mesons are only
expected to exist in the limit of large mass for the two-quark subsystem,
, since the calculated mass is below the
or thresholds.Comment: 10 pages, 5 tables. Accepted for publication in Phys. Rev.
Faddeev calculation of pentaquark in the Nambu-Jona-Lasinio model-based diquark picture
A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark
in the diquark picture of Jaffe and Wilczek in which is a
diquark-diquark- three-body system. Nambu-Jona-Lasinio (NJL) model is
used to calculate the lowest order diagrams in the two-body scatterings of
and . With the use of coupling constants determined from the
meson sector, we find that interaction is attractive in s-wave
while interaction is repulsive in p-wave. With only the lowest three-body
channel considered, we do not find a bound pentaquark state.
Instead, a bound pentaquark with is obtained with a
unphysically strong vector mesonic coupling constants.Comment: 22 pages, 11 figures, accepted version in Phys. Rev. C. Summary of
main changes/corrections: 1. "which only holds at tree level" below the eq.
(23) is added. 2. In the last paragraph of p.23 we added a remark that the
coupling constant obtained from Lambda mass is different from the estimate as
obtained from the meson spectru
Quark-quark correlations and baryon electroweak observables
The simple independent quark models have difficulties explaining
simultaneously the totality of the known hyperon magnetic moments and hyperon
semi-leptonic decay rates. We show that both the Goldstone boson loop
contributions and the two-quark effective exchange currents are essential in
explaining these observables.Comment: 7 pages, 1 figur
In-medium electron-nucleon scattering
In-medium nucleon electromagnetic form factors are calculated in the quark
meson coupling model. The form factors are typically found to be suppressed as
the density increases. For example, at normal nuclear density and , the nucleon electric form factors are reduced by approximately 8%
while the magnetic form factors are reduced by only 1 - 2%. These variations
are consistent with current experimental limits but should be tested by more
precise experiments in the near future.Comment: 14 pages, latex, 3 figure
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