Search

Recent lattice QCD calculations showed that a $d_{N��}$ dibaryon state similar to the deuteron with small binding energy may exist. In this work we propose a hadronic molecular approach to study the dynamical properties of this exotic state. We use a phenomenological Lagrangian approach to describe the coupling of the $d_{N��}$ state to its constituents and the decays into conventional hadrons, $d_{N��} \to ����$ and $d_{N��} \to ����$. Predictions for the sum of the decay rates are in the range of a few hundred keV. In addition, we find that the $d_{N��} \to ����$ mode is dominant, preferably searched for in a future RHIC experiment.

The $��$ meson gravitational form factors are studied based on a light-front constituent quark model which has been successfully employed to calculate its generalized parton distributions and some low-energy observables. The distributions of energy, spin, pressures, and shear forces inside the $��$ meson are explicitly given.

$d^\ast(2380)$ was observed by WASA-at-COSY collaborations in the nuclear reaction recently. Its particularly narrow width may indicate the new QCD-allowed hadronic structure. To further confirm the existence of this peculiar particle in a totally different kind of reaction, we study the opportunity for searching $\bar{d}^\ast$ in the $\Upsilon(nS)$ (with n=1, 2, 3) decay. As a phenomenological study, our framework is based on SU(3) chiral quark model. By virtue of the unitarity of $S$-matrix and crossing symmetry, we study the imaginary part of the forward scattering amplitudes between $\Upsilon(nS)$ and $d^\ast$. The scattering process is mainly governed by the quark-meson interaction. We examine both the pseudoscalar and vector meson contribution in the intermediate state. Hopefully, our results show that it's quite possible to find $\bar{d}^\ast$ in this decay mode in the future., Comment: 7 pages, 3 figures, 1 table

In this paper, the meson impact parameter dependent parton distributions and the impact parameter dependent form factors are introduced and discussed. By employing a Gaussian form wave packet, we calculate the impact parameter distributions of the meson based on a light-cone constituent quark model.

$d^\ast(2380)$ was observed by WASA-at-COSY collaborations in the nuclear reaction recently. Its particularly narrow width may indicate the new QCD-allowed hadronic structure. To further confirm the existence of this peculiar particle in a totally different kind of reaction, we study the opportunity for searching $\bar{d}^\ast$ in the $��(nS)$ (with n=1, 2, 3) decay. As a phenomenological study, our framework is based on SU(3) chiral quark model. By virtue of the unitarity of $S$-matrix and crossing symmetry, we study the imaginary part of the forward scattering amplitudes between $��(nS)$ and $d^\ast$. The scattering process is mainly governed by the quark-meson interaction. We examine both the pseudoscalar and vector meson contribution in the intermediate state. Hopefully, our results show that it's quite possible to find $\bar{d}^\ast$ in this decay mode in the future., 7 pages, 3 figures, 1 table

In this paper, the $��$ meson impact parameter dependent parton distributions and the impact parameter dependent form factors are introduced and discussed. By employing a Gaussian form wave packet, we calculate the impact parameter distributions of $��$ meson based on a light-front constituent quark model.

The electromagnetic form factors and low-energy observables of the deuteron are studied with the help of the light-front approach, where the deuteron is regarded as a weakly bound state of a proton and a neutron. Both the S and D wave interacting vertexes among the deuteron, proton, and neutron are taken into account. Moreover, the regularization functions are also introduced. In our calculations, the vertex and the regularization functions are employed to simulate the momentum distribution inside the deuteron. Our numerical results show that the light-front approach can roughly reproduce the deuteron electromagnetic form factors, like charge G0, magnetic G1, and quadrupole G2, in the low Q2 region. The important effect of the D wave vertex on G2 is also addressed.

We study $��$ meson unpolarized generalized parton distributions based on a light-front constituent quark model where the quark-antiquark-meson vertex is constructed under the symmetric loop momentum convention. The form factors and some other low-energy observables of the $��$ meson are calculated. Moreover, the contributions to the form factors and generalized parton distributions from the valence and nonvalence regimes are discussed and analyzed in detail. In the forward limit, the usual structure functions are estimated as well. In addition, by evolving the moments of the obtained structure functions to the scale of the lattice calculation, we give the factorization scale of our quark model. It is found that the present phenomenological model is reasonable to describe the general properties of $��$ meson.

We study the near-threshold incoherent $\phi$ photoproduction on the deuteron based on a model of $\gamma N \to \phi N$, consisting of Pomeron, $(\pi, \eta)$ exchanges, and a $J^P = 3/2^-$ resonance, which describes the low energy $\gamma p \to \phi p$ LEPS data well, including the peak in the forward differential cross section. The calculation is done up to double rescatterings, with the spin dependence of the elementary $\gamma N \to \phi N$ amplitude retained throughout the calculation. The Fermi motion and final-state interactions (FSI) are all properly treated as prescribed by realistic nucleon-nucleon interaction. The couplings of the resonance to $\gamma n$ and $\phi n$ channels are estimated with the help of a constituent quark model. The main features of the LEPS and CLAS data are described reasonably well except for some quantitative discrepancies at very low energies and low momentum transfers regions. It is found that contributions of Fermi motion, $pn$ FSI, and resonance are all indispensable in bridging the differences between the single-scattering results and the data. The off-shell rescattering is found to be important as it cancels out a large portion of the on-shell contribution. The discrepancies at low momentum transfer region might be related to the binning size of the data. No peak is found to be associated with the weak resonance as it gets smeared out by the Fermi motion and FSI with deuterium target. The problem at very low energy region hints at the possible contributions from other mechanisms and should be investigated in depth with the use of recent high statistics $\gamma p \to \phi p$ data from CLAS.

The electromagnetic form factors and low-energy observables of deuteron are studied with the help of the light-front approach, where the deuteron is regarded as a weekly bound state of a proton and a neutron. Both the $S-$ and $D-$wave interacting vertexes among deuteron, proton, and neutron are taken into account. Moreover, the regularization functions are also introduced. In our calculations, the vertex and the regularization functions are employed to simulate the momentum distribution inside the deuteron. Our numerical results show that the light-front approach can roughly reproduce the deuteron electromagnetic form factors, like charge $G_0$, magnetic $G_1$, and quadrupole $G_2$, in the low $Q^2$ region. The important role of the $D-$wave vertex on $G_2$ is also addressed.

The Q(2) dependencies of Roper resonance (N*(1440)) helicity amplitudes have been discussed based on two assumptions: (i) the Roper resonance is an excitation of one of the three quarks, and (ii) the quarks are surrounded by a pion-meson cloud. Our study shows that the mixing of the ground state in the Roper wavefunction caused by the pion meson cloud together with the pion meson cloud itself is crucial for the predictions of the photoproduction amplitudes of the Roper resonance. It is found that our model can give a good description for the helicity amplitudes of the Roper resonance comparing with the experimental measurement.

We study the nucleon form factors and the nucleon-△(1232)transitions in a framework of hypercentralconstituent quark model.The pion meson cloud effect is taken into account explicitly.Our results show that the pioncloud contributes substantially to the nucleon form factors as well as to the helicity amplitudes of △(1232),and it givesan improved agreement compared to the experimental measurement.

Quark–hadron duality of three proton spin structure functions g1, g2 and gT are discussed simultaneously. It is found that the onsets of the quark–hadron dualities of g1p, g2p and gTp are similar and they are expected to be at about Q2~2 GeV2. In addition, our results show that the elastic peak remarkably breaks local quark–hadron duality.

In this work, a subtle role of the pion meson cloud effect on the electric polarizabilities of the proton and neutron is stressed. It is shown that the electric polarizabilities of the proton and neutron, and the difference between the electric polarizabilities of the proton and neutron can be explained by including the pion meson cloud explicitly. However, the magnitude of the estimated mean-square charge radius of the neutron is still far from the measurement.

The ratio between the anomalous magnetic moments of proton and neutron has recently been suggested to be connected to the ratio of proton momentum fractions carried by the valence quarks inside it. This moment fraction ratio is respectively evaluated by using constituent quark model and chiral quark model in order to check meson cloud effect. Our results show that the meson cloud effect is remarkable to the ratio of the proton momentum fractions, and therefore, this ratio is a sensitive test for the meson cloud effect as well as for the SU(6) symmetry breaking effect.

In this paper, by using harmonic-oscillator wave functions of different interaction models, i.e. OPE (one-pion-exchange model), OPsE (only pseudoscalar meson exchange model), the extended GBE (Goldstone-boson-exchange model including vector and scalar mesons), and OGE (one-gluon-exchange model), we calculate and compare the strong decays of negative parity N* resonances under 2 GeV. We find that the conventional mixing angles are correct, and GBE and OGE are obviously superior to OPE and OPsE.

The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance . Our analysis indicates that the constraints of the transition amplitude for the resonance at the limit by QCD sum rule calculations are not applicable at a moderate range of compared with the present available data if the contribution of is dominant in the limit.

Calculations of helicity amplitudes for the low-lying nucleon resonances are displayed based on a non-relativistic constituent quark model with a harmonic oscillator confinement. The explicit effect of quark confinement isshown. Our results show that the effect plays sizable role on some transition amplitudes of S11(1535) and D13(1520)resonances. The effect on the △(1232) transition amplitudes islessthan 10%. However, the effect on the Roper resonanceis remarkable but is inconclusive.

Based on a simple nonrelativistic constituent quark model, the nucleon structure function F-2 in the resonance region is estimated by taking the contributions from low-lying nucleon resonances into account. Calculated results are employed to study quark-hardon duality in the nucleon electron scattering process by comparing them to the scaling behavior from the data in deep inelastic scattering region.

Spin-independent relativistic effect on binding and dissociation of heavy quarkonium in a thermal environment is stressed. The calculated result shows that the effect considerably influences the spin-averaged thermal properties of the system. As a result, it should be considered in future experiments at RHIC.

The binding and dissolution of heavy quarkonium are investigated with a temperature-dependent screening quark potential model. The results show that the color screening effect considered by lattice gauge calculation at temperature T=0 plays an important role on the determination of the critical screened mass of the high-lying excited state of heavy quarkonium.

In this paper the Jaffe - Lipkin model is modified and extended to the calculations of spin-dependent properties of the nucleon with the considerations of the quark-exchange effect and the non-strange isovector sea pairs.

In this paper, the spectra of heavy flavor hadrons, such as heavy flavor mesons [Formula: see text], baryons (QQq and Qqq) and multiquark systems [Formula: see text], are studied systematically based on the heavy quark effective theory. The calculated results of [Formula: see text] are compared with the predictions of the potential model.

The discrepancy between the PQCD calculation and the CLEO data for $��_{c1}\to ��V$ ($V=��^0,\,��,\,��$) stimulates our interest in exploring extra mechanism of $��_{c1}$ decay. In this work, we apply an important non-perturbative QCD effect, i.e., hadronic loop mechanism, to study $��_{c1}\to ��V$ radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of $��_{c1}\to ��V$ are consistent with the corresponding CLEO data of $��_{c1}\to ��V$. We expect further experimental measurement of $��_{c1}\to ��V$ at BES-III, which will be helpful to test the hadronic loop effect on $��_{c1}$ decay., 7 pages, 2 figures. Accepted for publication in Eur. Phys. J. C

We derive the exchange currents of pseudoscalar, vector, and scalar mesons from Feynman diagrams, and use them to calculate the magnetic form factors of nucleon and $\Delta(1232)$. The magnetic moments and electromagnetic radii are obtained by using those form factors and the parameters determined from the masses of nucleon and $\Delta(1232)$. We find the magnetic moments and electromagnetic radii of nucleon and $\Delta(1232)$ can be produced very well in the extended Goldstone-boson-exchange model (GBE) in which all of pseudoscalar, vector and scalar meson nonet are included. The magnetic moments of $\Delta(1232)$ are closer to experiment values and results from lattice calculation than the results obtained by the model without other mesons except for pion and sigma., Comment: 15 pages,5 figures

In this Brief Report, by using the mixing angles of the one-gluon-exchange (OGE) and one-pion-exchange (OPE) models, and by using the electromagnetic Hamiltonian of Close and Li, we calculate the amplitudes of L = 1 N* resonances for photoproduction and electroproduction. The results are compared to experimental data. It is found that the data support OGE, not OPE.

To study the polarized gluon density Δg(x) in the nucleon, we propose the high-pT pair charmed hadron production process in polarized lp scattering. The double spin asymmetry ALL for this process is a good observable for testing the models of Δg(x).