2,818 research outputs found
Radiative production of the Lambda(1405) resonance in K collisions on protons and nuclei
We have carried a theoretical study of the K^- p\to M B \gamma reaction with
M B = K^-p, \bar{K}^0 n, \pi^- \Sigma^+, \pi^+ \Sigma^-, \pi^0 \Sigma^0, \pi^0
\Lambda, for K^- lab. momenta between 200 and 500 MeV/c, using a chiral unitary
approach for the strong K^-p interaction with its coupled channels. The
\Lambda(1405) resonance, which is generated dynamically in this approach, shows
up clearly in the d\sigma/dM_I spectrum, providing new tests for chiral
symmetry and the unitary approach, as well as information regarding the nature
of the resonance. The photon detection alone, summing all channels, is shown to
reproduce quite accurately the strength and shape of the \Lambda(1405)
resonance. Analogous reactions in nuclei can provide much information on the
properties of this resonance in a nuclear medium.Comment: 11 pages, 3 postscripts figure
Pentaquark in nuclear matter and hypernuclei
We study the properties of the in nuclear matter and
hypernuclei within the quark mean-field (QMF) model, which has been
successfully used for the description of ordinary nuclei and
hypernuclei. With the assumption that the non-strange mesons couple only to the
and quarks inside baryons, a sizable attractive potential of the
in nuclear matter is achieved as a consequence of the cancellation
between the attractive scalar potential and the repulsive vector potential. We
investigate the single-particle energies in light, medium, and heavy
nuclei. More bound states are obtained in hypernuclei in comparison
with those in hypernuclei.Comment: 16 pages, 5 figure
Strange meson-nucleon states in the quark potential model
The quark potential model and resonating group method are used to investigate
the bound states and/or resonances. The model potential consists of
the t-channel and s-channel one-gluon exchange potentials and the confining
potential with incorporating the QCD renormalization correction and the
spin-orbital suppression effect in it. It was shown in our previous work that
by considering the color octet contribution, use of this model to investigate
the low energy elastic scattering leads to the results which are in pretty
good agreement with the experimental data. In this paper, the same model and
method are employed to calculate the masses of the bound systems.
For this purpose, the resonating group equation is transformed into a standard
Schr\"odinger equation in which a nonlocal effective interaction
potential is included. Solving the Schr\"odinger equation by the variational
method, we are able to reproduce the masses of some currently concerned
states and get a view that these states possibly exist as
molecular states. For the system, the same calculation gives no support to
the existence of the resonance which was announced
recently.Comment: 15 pages, 4 figure
Description of Drip-Line Nuclei within Relativistic Mean-Field Plus BCS Approach
Recently it has been demonstrated, considering Ni and Ca isotopes as
prototypes, that the relativistic mean-field plus BCS (RMF+BCS) approach
wherein the single particle continuum corresponding to the RMF is replaced by a
set of discrete positive energy states for the calculation of pairing energy
provides a good approximation to the full relativistic Hartree-Bogoliubov (RHB)
description of the ground state properties of the drip-line neutron rich
nuclei. The applicability of RMF+BCS is essentially due to the fact that the
main contribution to the pairing correlations is provided by the low-lying
resonant states. General validity of this approach is demonstrated by the
detailed calculations for the ground state properties of the chains of isotopes
of O, Ca, Ni, Zr, Sn and Pb nuclei. The TMA and NL-SH force parameter sets have
been used for the effective mean-field Lagrangian. Comprehensive results for
the two neutron separation energy, rms radii, single particle pairing gaps and
pairing energies etc. are presented. The Ca isotopes are found to exhibit
distinct features near the neutron drip line whereby it is found that further
addition of neutrons causes a rapid increase in the neutron rms radius with
almost no increase in the binding energy, indicating the occurrence of halos. A
comparison of these results with the available experimental data and with the
recent continuum relativistic Hartree-Bogoliubov (RCHB) calculations amply
demonstrates the validity and usefulness of this fast RMF+BCS approach.Comment: 59 pages, 40 figure
Rho-Nucleon Tensor Coupling and Charge-Exchange Resonances
The Gamow-Teller resonances are discussed in the context of a self-consistent
RPA, based on the relativistic mean field theory. We inquire on the possibility
of substituting the phenomenological Landau-Migdal force by a microscopic
nucleon-nucleon interaction generated from the rho-nucleon tensor coupling. The
effect of this coupling turns out to be very small when the short range
correlations are not taken into account, but too large when these correlations
are simulated by the simple extraction of the contact terms from the resulting
nucleon-nucleon interaction.Comment: 15 pages, LaTeX, 2 figures; extended text, improved figures, new
references added, the version appearing in Phys.Lett.
Analyzing powers in inclusive pion production at high energy and the nucleon spin structure
Analyzing powers in inclusive pion production in high energy transversely
polarized proton-proton collisions are studied theoretically in the framework
of the quark recombination model. Calculations by assuming the SU(6)
spin-flavor symmetry for the nucleon structure disagree with the experiments.
We solve this difficulty by taking into account the %We overcome this
difficulty by taking into account the realistic spin distribution functions of
the nucleon, which differs from the SU(6) expectation at large , %but
coincides with a perturbative QCD constraint on the ratio of the unpolarized
valence distributions, as . We also discuss the kaon spin
asymmetry and find in the polarized proton-proton
collisions at large .Comment: 13 pages, 4 figures, late
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
Chiral SU(3) Bethe Salpeter Model: Extension to SU(6) and SU(8) Spin-Flavor Symmetries
Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor
Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which
incorporate vector meson degrees of freedom. In the charmless sector, the
on-shell approximation to the Bethe-Salpeter (BS) approach successfully
reproduces previous SU(3) WT results for the lowest-lying s--wave negative
parity baryon resonances. It also provides some information on the dynamics of
heavier ones and of the lightest d-wave negative parity resonances, as e.g. the
Lambda(1520). For charmed baryons the scheme is consistent with heavy quark
symmetry, and our preliminary results in the strangeness-less charm C=+1 sector
describe the main features of the three-star J^P=1/2^- Lambda_c(2595) and
J^P=3/2^- Lambda_c(2625) resonances. We also find a second broad J^P=1/2^-
state close to the Lambda_c(2595)Comment: Presented at Chiral07: Chiral Symmetry in Hadron and Nuclear Physics
November 13-16, 2007, Osaka University, Japa
Quark mean field model with density dependent couplings for finite nuclei
The quark mean field model, which describes the nucleon using the constituent
quark model, is applied to investigate the properties of finite nuclei. The
couplings of the scalar and vector mesons with quarks are made density
dependent through direct coupling to the scalar field so as to reproduce the
relativistic Brueckner-Hartree-Fock results of nuclear matter. The present
model provides satisfactory results on the properties of spherical nuclei, and
predicts an increasing size of the nucleon as well as a reduction of the
nucleon mass in the nuclear environmentComment: 8 pages, REVTeX, 8 ps figures, accepted for publication in Phys. Rev.
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