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1.
C. Garcıa-Recio J. Nieves L. L. Salcedo 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):540-542
Starting from a consistent SU(6) extension of the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian ( Phys. Rev. D 74, 034025 (2006)), we study the s-wave meson-baryon resonances in the strangeness S = - 3 and negative-parity sectors. Those resonances are generated by solving the Bethe-Salpeter equation with the WT interaction
used as kernel. The considered mesons are those of the 35-SU(6)-plet, which includes the pseudoscalar (PS) octet of pions and the vector (V) nonet of the rho-meson. For baryons we consider
the 56-SU(6)-plet, made of the 1/2+ octet of the nucleon and the 3/2+ decuplet of the Delta. Quantum numbers I(J
P) = 0(3/2-) are suggested for the experimental resonances Ω
*(2250)- and Ω
*(2380)-. Among other, resonances with I = 1 are found, which minimal quark content is sssˉl', being s the strange quark and l, l' any of the the light up or down quarks. A clear signal for such a pentaquark would be a baryonic resonance with strangeness -3 and electric charge -2 or
0, in proton charge units. We suggest looking for K
-
Ξ
- resonances with masses around 2100 and 2240MeV in the sector 1(1/2-), and for π
±
Ω
- and K
-
Ξ
*- resonances with masses around 2260MeV in the sector 1(3/2-). 相似文献
2.
A SU(4) flavor symmetrical Lagrangian is constructed for the interaction of the pseudo-scalar mesons with the vector mesons. SU(4) symmetry is broken to SU(3) by suppression of terms in the Lagrangian where the interaction should be driven by charmed mesons. Chiral symmetry can
be restored by setting this new SU(4) symmetry-breaking parameters to zero. Unitarization in coupled channels leads to the dynamical generation of resonances.
Many known axial resonances can be identified including the new controversial X(3872) and the structure found recently by Belle around 3875MeV in the hidden charm sector. Also new resonances are predicted,
some of them with exotic quantum numbers. 相似文献
3.
C. Garcıa-Recio J. Nieves L. L. Salcedo 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):491-494
The construction of an extended version of the Weinberg-Tomozawa Lagrangian, in which baryons and mesons form spin-flavor
multiplets, is reviewed and some of its properties discussed, for an arbitrary number of colors and flavors. The coefficient
tables of spin-flavor irreducible representations related by crossing between the s-, t- and u-channels are explicitly constructed. 相似文献
4.
The Bethe-Salpeter (BS) equation in Minkowski space for scalar particles is solved for a kernel given by a sum of ladder and
cross-ladder exchanges. The solution of corresponding light-front (LF) equation, where we add the time-ordered stretched boxes,
is also obtained. Cross-ladder contributions are found to be very large and attractive, whereas the influence of stretched
boxes is negligible. Both approaches --BS and LF-- give very close results. 相似文献
5.
We develop a new method of solving the Bethe-Salpeter (BS) equation in Minkowski space. It is based on projecting the BS equation
on the light-front (LF) plane and on the Nakanishi integral representation of the BS amplitude. This method is valid for any
kernel given by the irreducible Feynman graphs. For massless ladder exchange, our approach reproduces analytically the Wick-Cutkosky
equation. For massive ladder exchange, the numerical results coincide with the ones obtained by Wick rotation. 相似文献
6.
S. Migura D. Merten B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2006,28(1):41-53
We calculate mass spectra of charmed baryons within a relativistically covariant quark model based on the Bethe-Salpeter equation
in instantaneous approximation. Interactions are given by a linearly rising three-body confinement potential and a flavor-dependent
two-body force derived from QCD instanton effects. This model has already been successfully applied to the calculation of
light flavor baryon spectra and is now extended to heavy baryons. Within the same framework we compare the results to those
obtained with the more conventional one-gluon exchange potential. 相似文献
7.
8.
C. Haupt B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2006,28(2):213-225
We show that static properties like the charge radius and the magnetic moment of relativistic three-fermion bound states with
instantaneous interactions can be formulated as expectation values with respect to intrinsically defined wave functions. The
resulting operators can be given a natural physical interpretation in accordance with relativistic covariance. We also indicate
how the formalism may be generalized to arbitrary moments. The method is applied to the computation of static baryon properties
with numerical results for the nucleon charge radii and the baryon octet magnetic moments. In addition, we make predictions
for the magnetic moments of some selected nucleon resonances and discuss the decomposition of the nucleon magnetic moments
in contributions of spin and angular momentum, as well as the evolution of these contributions with decreasing quark mass. 相似文献
9.
L. Campos Venuti C. Degli Esposti Boschi E. Ercolessi G. Morandi F. Ortolani S. Pasini M. Roncaglia 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):11-18
Motivated by field-theoretic predictions we investigate the stable
excitations that exist in two characteristic gapped phases of a spin-1
model with Ising-like and single-ion anisotropies. The sine-Gordon
theory indicates a region close to the phase boundary where a stable
breather exists besides the stable particles, that form the Haldane
triplet at the Heisenberg isotropic point. The numerical data, obtained
by means of the Density Matrix Renormalization Group, confirm this
picture in the so-called large-D phase for which we give also a
quantitative analysis of the bound states using standard perturbation
theory. However, the situation turns out to be considerably more intricate
in the Haldane phase where, to the best of our data, we do not observe
stable breathers contrarily to what could be expected from the sine-Gordon
model, but rather only the three modes predicted by a novel anisotropic
extension of the Non-Linear Sigma Model studied here by means of a
saddle-point approximation. 相似文献
10.
A. Sibirtsev H. -W. Hammer U. -G. Meißner A. W. Thomas 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):209-220
We study coherent and incoherent φ-meson photoproduction from nuclei. The available data are analyzed in terms of single-
and coupled-channel photoproduction. It is found that the data on coherent photoproduction can be well reproduced within a
single-channel optical model and show only little room for ω-φ mixing. These data indicate a normal distortion of the φ-meson
in nuclei, which is compatible with the results obtained through the vector meson dominance model. The data on incoherent
φ-meson photoproduction show an anomalous A-dependence resulting in a very strong φ-meson distortion. These data can be explained by a coupled-channel effect through
the dominant contribution from the ω↦φ or the π↦φ transition or, more speculative, through the excitation of a cryptoexotic
B
φ-baryon. 相似文献
11.
We use phenomenological nonlocal Lagrangians, which lead to nontrivial forms for the quark propagator, to describe the pion.
We define a procedure based on previous studies on nonlocal Lagrangians for the calculation of the pion parton distributions
at low Q2. The obtained parton distributions fulfill all the wishful properties. Using a convolution approach we incorporate the composite
character of the constituent quarks. We evolve, using the Renormalization Group, the calculated parton distributions to the
experimental scale and compare favorably with the data and draw conclusions. 相似文献
12.
Form factors are calculated in the point form of relativistic quantum mechanics for the lowest energy states of a system made
of two scalar particles interacting via the exchange of a massless boson. They are compared to the exact results obtained
by using solutions of the Bethe-Salpeter equation which are well known in this case (Wick-Cutkosky model). The relevance of
the comparison is examined by considering other relativistic quantum-mechanics approaches where results are known or have
been obtained recently. Deficiencies of the point-form approach together with the single-particle current are emphasized.
They point to quite sizeable contributions of two-body currents. These ones are required to fulfil current conservation in
any case and to reproduce the high momentum transfer behaviour expected from the Born amplitude.
Received: 11 July 2001 / Accepted: 12 February 2002 相似文献
13.
The kinematical corrections to the structure function of the nucleon in the nucleus due to the boundness and motion of nucleons arise from the excitation of the doorway states for one-nucleon transfer reactions in the deep inelastic scattering on nuclei. 相似文献
14.
S. Migura D. Merten B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2006,28(1):55-62
We calculate semileptonic decays of light and heavy baryons in a relativistically covariant constituent quark model. The model
is based on the Bethe-Salpeter equation in instantaneous approximation. It generates satisfactory mass spectra for mesons
and baryons up to the highest observable energies. Without introducing additional free parameters we compute on this basis
helicity amplitudes of electronic and muonic semileptonic decays of baryons. We thus obtain form factor ratios and decay rates
in good agreement with experiment. 相似文献
15.
We present results for the helicity amplitudes of the lowest-lying hyperon resonances Y*, computed within the framework of the Bonn Constituent-Quark model, which is based on the Bethe-Salpeter approach. The seven
parameters entering the model were fitted to the best-known baryon masses. Accordingly, the results for the helicity amplitudes
are genuine predictions. Some hyperon resonances are seen to couple more strongly to a virtual photon with finite Q2 than to a real photon. Other Y*'s, such as the S01(1670) Λ-resonance or the S11(1620) Σ-resonance, couple very strongly to real photons. We present a qualitative argument for predicting the behaviour of
the helicity asymmetries of baryon resonances at high Q2.-1 相似文献
16.
17.
P. Costa C. A. de Sousa M. C. Ruivo Yu. L. Kalinovsky 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):842-844
We study the chiral phase transition at finite T and μ
B within the framework of the SU(3) Nambu-Jona-Lasinio (NJL) model. The QCD critical end point (CEP) and the critical line at finite temperature and baryonic
chemical potential are investigated: the study of physical quantities, such as the baryon number susceptibility near the CEP,
will provide complementary information concerning the order of the phase transition. We also analyze the information provided
by the study of the critical exponents around the CEP. 相似文献
18.
T. Van Cauteren J. Ryckebusch B. Metsch H. -R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):613-615
We present some of our results for the electromagnetic properties of excited Σ hyperons, computed within the framework of the Bonn constituent-quark model, which is based on the Bethe-Salpeter approach.
The seven parameters entering the model are fitted against the best-known baryon masses. Accordingly, the results for the
form factors and helicity amplitudes are genuine predictions. We compare with the scarce experimental data available and discuss
the processes in which Σ
*'s may play an important role. 相似文献
19.
We investigate the spin-3/2 baryons in the 27-plet based on flavor SU(3) symmetry. For J
p = 3/2+, we find all the candidates for non-exotic members. For J
p = 3/2-, we predict a new non-exotic member Λ(1780). Fitting the mass spectrum and calculating the widths of the members show an
approximate symmetry of the 27-plet of SU(3). We find that the exotic members have relatively large widths and the Ξ(1950) has spin and parity J
p = 3/2-. The possibility of assigning the non-exotic candidates to an octet is also analyzed. 相似文献
20.
M. Koll R. Ricken D. Merten B.C. Metsch H.R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):73-94
We present new results of a relativistic quark model based on the Bethe-Salpeter equation in its instantaneous approximation.
Assuming a linearly rising confinement potential with an appropriate spinorial structure in Dirac space and adopting a residual
interaction based on instanton effects, we can compute masses of the light mesons up to highest observed angular momenta with
a natural solution of the U
A(1) problem. The calculated ground states masses and the radial excitations describe the experimental results well. In this
paper, we will also discuss our results concerning numerous meson decay properties. For processes like π+/K
+↦e
+υeγ and 0-↦γγ at various photon virtualities, we find a good agreement with experimental data. We will also comment on the form factors
of the K
?3 decay and on the decay constants of the π, K and η mesons. For the sake of completeness, we will furthermore present the electromagnetic form factors of the charged π
and K mesons as well as a comparison of the radiative meson decay widths with the most recent experimental data.
Received: 28 August 2000 / Accepted: 12 September 2000 相似文献