Search

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.

We investigate the mass spectrum of the $ss \bar s \bar s$ tetraquark states within the relativized quark model. By solving the Schr\"{o}dinger-like equation with the relativized potential, the masses of the $S-$ and $P-$wave $ss \bar s \bar s$ tetraquarks are obtained. The screening effects are also taken into account. It is found that the observed resonant structure $X(2239)$ in the $e^+e^- \to K^+K^-$ process by BESIII Collaboration can be assigned as a $P-$wave $1^{--}$ $ss \bar s \bar s$ tetraquark state. Furthermore, the radiative transition and strong decay behaviors of this structure are also estimated, which can provide helpful information for future experimental searches., Comment: 7 pages, 2 figures. Add the strong decay behaviors. Version accepted by Chinese Physics C

The $\rho$ meson polarized generalized parton distribution functions, its structure functions $g_1$ and $g_2$ and its axial form factors ${\tilde G}_{1,2}$ are studied based on a light-front quark model for the first time. Comparing our obtained moments of $g_1$ to lattice QCD calculation, we find that our results are reasonably consistent to the Lattice predictions.

$d^\ast(2380)$ 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 $��$ meson polarized generalized parton distribution functions, its structure functions $g_1$ and $g_2$ and its axial form factors ${\tilde G}_{1,2}$ are studied based on a light-front quark model for the first time. Comparing our obtained moments of $g_1$ to lattice QCD calculation, we find that our results are reasonably consistent to the Lattice predictions.

There are polarized structure functions $b_{1-4}$ for the spin-1 deuteron. We calculated the leading-twist tensor structure function $b_1$ by using convolution description for the deuteron. We found large differences between our theoretical functions and HERMES experimental data on $b_1$. Although higher-twist effects should be considered in obtaining experimental $b_1$, it suggests a possible existence of new hadron physics mechanism for spin-1 hadrons. Furthermore, we found that there are significant distributions at large Bjorken $x$. In future, an experimental measurement is planned at JLab for $b_1$ and there is a possibility of a proton-deuteron Drell-Yan experiment at Fermilab with the tensor-polarized deuteron, so that further theoretical studies are needed for clarifying the physics origin of tensor structure in terms of quark and gluon degrees of freedom., 4 pages, 2 eps figures, 22nd International Spin Symposium (Spin-2016), University of Illinois, Champaign, Illinois, USA, September 25-30, 2016

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 strong decay channels $P_c^+(4380) \to J/\psi p$ and $P_c^+(4450) \to J/\psi p$ under $\Sigma_c \bar{D}^*$ molecular state ansatz. With various spin-parity assignments, the partial decay widths of $J/\psi p$ final state are calculated. Our results show that all the $P$ wave $\Sigma_c {\bar D}^*$ assignments are excluded, while $S$ wave $\Sigma_c {\bar D}^*$ pictures for $P_c(4380)$ and $P_c(4450)$ are both allowed by present experimental data. The $J^P=3/2^-$ $\Sigma_c^* \bar{D}$ and $\Sigma_c^* \bar{D}^*$ molecules are also discussed in the heavy quark limit, and find that the $\Sigma_c^* \bar{D}$ system for $P_c(4380)$ is possible. More experimental information on spin-parities and partial decay widths and theoretical investigations on other decay modes are needed to clarify the nature of the two $P_c$ states., Comment: 7 pages, 6 figures, 2 tables. More discussions are added. Version accepted by Phys. Rev. D

We study the strong decay channels $P_c^+(4380) \to J/��p$ and $P_c^+(4450) \to J/��p$ under $��_c \bar{D}^*$ molecular state ansatz. With various spin-parity assignments, the partial decay widths of $J/��p$ final state are calculated. Our results show that all the $P$ wave $��_c {\bar D}^*$ assignments are excluded, while $S$ wave $��_c {\bar D}^*$ pictures for $P_c(4380)$ and $P_c(4450)$ are both allowed by present experimental data. The $J^P=3/2^-$ $��_c^* \bar{D}$ and $��_c^* \bar{D}^*$ molecules are also discussed in the heavy quark limit, and find that the $��_c^* \bar{D}$ system for $P_c(4380)$ is possible. More experimental information on spin-parities and partial decay widths and theoretical investigations on other decay modes are needed to clarify the nature of the two $P_c$ states., 7 pages, 6 figures, 2 tables. More discussions are added. Version accepted by Phys. Rev. D

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.

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.

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.

By employing the parametrization form of the nucleon spin structure function in the resonance region, which includes the contributions of the resonance peaks and of nonresonance background, we study Bloom–Gilman quark-hadron duality of g1 both in the inelastic resonance region and elastic one.

We estimate the correction of relativistic center-of-mass vector on electric polarizability of an equal-mass quark-antiquark system numerically. Effect on the system confined by different interactive potentials is analysed. A great improvement for the electric polarizability of pion meson is obtained.

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.

Based on a relativistic quark model approach with an effective potential U(r) = (ac/2)(1 + γ0)r2, the spin content of the nucleon is investigated. Pseudo-scalar interaction between quarks and Goldstone bosons is employed to calculate the couplings between the Goldstone bosons and the nucleon. Different approaches to deal with the center of mass correction in the relativistic quark potential model approach are discussed.

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.

By solving the eigenvalue equation for the quark-antiquark potential which emerges from an effective dilaton-gluon coupling inspired by superstring theory, we obtain the spin-averaged energy levels of charmonium (c) and bottonium (b) and show that the masses of the c and b states are well in agreement with the available experimental data.

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

Two-photon annihilate contributions in the process $e^+ + e^- \to p + \bar{p}$ including $N$ and $��$ intermediate are discussed in a simple hadronic model. The corrections to the unpolarized cross section and polarized observables $P_x,P_z$ are presented. The results show the two-photon annihilate correction to unpolarized cross section is small and its angle dependence becomes weak at small $s$ after considering the $N$ and $��(1232)$ contributions simultaneously, while the correction to $P_z$ is enhanced., 5 pages

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

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 $��(1232)$. The magnetic moments and electromagnetic radii are obtained by using those form factors and the parameters determined from the masses of nucleon and $��(1232)$. We find the magnetic moments and electromagnetic radii of nucleon and $��(1232)$ 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 $��(1232)$ 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., 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.

The leptonic decay of charmonium is studied by using an error function confinement potential in which the color-screening effect is considered. The relativistic correction of the quark-antiquark potential is also included in the calculation. The discrepancy means that there should be some other effects in explaining charmonium high-lying states.

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).