Search

The dynamic mechanism of short range interaction between $u/d$ quarks is still an open and challenging problem. In order to reveal this quark dynamics, we perform a systematic analysis of $NN$, $D_{03}$, and $D_{30}$ systems in the (extended) chiral SU(3) constituent quark models. By comparing results calculated with different models and different parameter sets, the effects of one gluon exchange and vector meson exchange terms are carefully examined. The results indicate that the vector meson exchange interactions dominate the short range interactions between $u/d$ quarks, while the small residual one gluon exchange coupling strength is also allowed., Comment: 8 pages, 2 figures, comments and suggestions are welcome

In present work, we perform a coupled-channel analysis of $B^{(*)}_{(s)}\bar{B}^{(*)}_{(s)}$ systems with the one-boson-exchange potentials. We first study the $I(J^{PC})=1(1^{+-})$ $B\bar{B}^{*}/B^{*}\bar{B}^{*}$ system to describe the $Z_{b}(10610)$ and $Z_{b}(10650)$ particles as molecular states and determine the reasonable range of cutoff parameter $\Lambda$. Then, other $B^{(*)}_{(s)}\bar{B}^{(*)}_{(s)}$ combinations with different quantum numbers are systematically investigated. Some bound states and resonances appear in the isoscalar systems, while only several shallow bound states exist for isovector systems. Far away from the excited conventional $P-$wave bottomium, these predicted states can be easily identified as exotic particles both theoretically and experimentally. Moreover, the $\eta_b(nS)/\Upsilon(nS)$ plus light mesons are the excellent final states to search for the bound states, while the $B\bar B^*+h.c.$ and $B^* \bar B^*$ channels are suitable for the resonances. We highly recommend that the LHCb and Belle II Collaborations can hunt for these bottomonium-like states in future., Comment: 9 pages, 3 figures, comments and suggestions are welcome

We adopt the quark pair creation model to investigate the light meson emissions of several charmonium-like states. The quark pair creation model is applied to the four-body systems, and we calculate the pion/kaon emissions of the $X(4700)$, $Z_c(4430)$, $Y(4230)$, $Y(4360)$, $Y(4390)$ and $Y(4660)$ within the compact tetraquark assumptions. It is found that the pion/kaon decay widths for the $X(4700)$ and $Z_c(4430)$ are relatively small, while the partial decay widths for the resonances $Y(4230)$, $Y(4360)$, $Y(4390)$ and $Y(4660)$ are significant. We expect that our exploration of these decay behaviors can provide useful information for future experimental searches and theoretical interpretations., Comment: 10 pages, 4 figures, to be published in Chinese Physics C

In this work, we propose to investigate the $d_{N\Omega}$ dibaryon production in the process $K^- p \rightarrow d_{N\Omega} \bar{\Xi}^0$ by utilizing the kaon beam with the typical momentum to be around 10 GeV, which may be available at COMPASS, OKA@U-70 and SPS@CERN. The cross sections for $K^- p \rightarrow d_{N\Omega} \bar{\Xi}^0$ are estimated and in particular, the magnitude of the cross sections are evaluated to be several hundreds nanobarn at $P_K=20$ GeV. Considering that $d_{N\Omega}$ dibaryon dominantly decay into $\Xi \Lambda$ and $\Xi \Sigma$, we also estimate the cross sections for $K^- p \to \Xi^0 \Lambda \bar{\Xi}^0$ and $K^- p \to \Xi^- \Sigma^+ \bar{\Xi}^0$, where the $d_{N\Omega}$ dibaryon can be observed in the invariant mass distributions of $\Xi^0 \Lambda$ and $\Xi^- \Sigma^+ $, respectively., Comment: 7 pages, 4 figures

Inspired by the recent observation of a new structure, $X(4014)$, in the process $\gamma\gamma\to \gamma\psi(2S)$, we evaluate the possibility of assigning $X(4014)$ as a $D^\ast \bar{D}^\ast$ molecular state with $I(J^{PC})=0(0^{++})$ by investigating the hidden charm decays of $X(4014)$. The partial widths of $J/\psi\omega$, $ \eta_{c}\eta$ and $\eta_{c}\eta^{\prime}$ channels are evaluated to be about $(0.41\sim 5.00)$, $(2.05\sim7.49)$ and $(0.11\sim0.51)\ \mathrm{MeV}$, respectively. Considering the experimental observation and the present estimations, we proposed to search $X(4014)$ in the $\gamma \gamma \to J/\psi \omega$ process in Belle II., Comment: 7 pages, 5 figures, accepted for publication in Phys. Rev. D

In this work, we systematically investigate the mass spectra of fully-heavy hexaquarks within a constituent quark model by including the color Coulomb potential, linear confining potential, and spin-spin interactions. Our results show that all of the fully-heavy hexaquarks lie above the corresponding baryon-baryon thresholds, and thus no stable compact one exists. These states may subsist as resonances and decay into two fully-heavy baryons easily through the fall-apart mechanism, which can be searched in future experiments., Comment: 8 pages, 2 figures, comments and suggestions are welcome

In this paper, we adopt an extended relativized quark model to investigate the triply-heavy tetrquarks systematically. The mass spectra are obtained by solving the four-body relativized Hamiltonian including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections. We find that all of the triply-heavy tetraquarks lie above the corresponding meson-meson thresholds, and thus no stable one exists. In particular, besides the spin-spin interactions, the Coulomb and confining potentials also contribute to the mass splittings in the $cb\bar c \bar q$ and $cb\bar b \bar q$ systems. Moreover, the whole mass spectra for triply heavy tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. Through the fall-apart mechanism, the triply-heavy tetraquarks may easily decay into the heavy quarkonium plus heavy-light mesons, which are good candidates for investigation in future experiments., Comment: 15 pages, 4 figures. Minor modifications, accepted version

In this work, the strong decay behaviors of the $\lambda-$mode low-lying $\Xi_{b}$ and $\Xi_{b}^\prime$ baryons are investigated within the $^3P_0$ model. Our results suggest that all of the low-lying $\bar 3_F$ states $\Xi_b(2S)$, $\Xi_b(1P)$, and $\Xi_b(1D)$ have small decay widths of less than 20 MeV, and these states have good potentials to be observed in the $\Xi_b^\prime \pi$ and $\Xi_b^{\prime *} \pi$ invariant masses. Further, most of the $6_F$ multiplets are relatively narrow and may decay into the $\Xi_b \pi$, $\Xi_b^\prime \pi$, $\Xi_b^{\prime *} \pi$, and $\Lambda_b \bar K$ final states. Considering the masses and strong decay behaviors, we can assign the newly observed $\Xi_{b}(6100)$ resonance as the $\Xi_b(1P)$ state with $J^P=3/2^-$ and interpret the $\Xi_{b}(6227)$ structure as the $J^P=3/2^-$ $\Xi_b^\prime(1P)$ state with a proper mixing angle. We expect that our predictions for these excited bottom strange baryons will provide helpful information for future experimental research., Comment: 7 pages, 3 figures. Minor modifications, accepted version

In this work, we investigated the decays of the fully open-flavor tetraquark state $X_0(2900)$ which was observed by the LHCb Collaboration very recently. Here, the $X_0(2900)$ was assigned as a $S-$wave $\bar D^\ast K^\ast$ hadronic molecule with $I=0$, and the effective lagrangian approach was applied to estimate the partial decay widths. Moreover, we also predicted the decay behaviors of the other unobserved $X_{J(J=1,2)}$, which were the spin partners of the $X_0(2900)$ in the $S-$wave $\bar D^\ast K^\ast$ picture. It was pointed out that the $X_1$ state with $I=0$ was a broad state with the width more than one hundred MeV, while another $X_2$ state with $I=0$ was a narrow state with the width approaching half of that for the $X_0(2900)$. In addition, our results also showed that the $\bar D^\ast K$ mode was expected to be the dominant decay mode for both $X_1$ and $X_2$. Searching for those unobserved $X_{J(J=1,2)}$ in the future experiments might be helpful to understand the nature of $X_0(2900)$.

In present work, we systematically calculate the mass spectra of open charm and bottom tetraquarks $q q\bar q \bar Q$ within an extended relativized quark model. The four-body relativized Hamiltonians including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved by using the variational method. It is found that the predicted masses of four $0^+$ $ud\bar s \bar c$ states are 2765, 3065, 3152, and 3396 MeV, which disfavor the assignment of the newly observed $X_0(2900)$ as a compact tetraquark. Moreover, the whole mass spectra of the open charm and bottom tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. In addition, our results suggest that the flavor exotic states $nn\bar s \bar c$, $nn\bar s \bar b$, $ss\bar n \bar c$, and $ss\bar n \bar b$ and their antiparticles can be searched in the heavy-light meson plus kaon final states by future experiments. More theoretical and experimental efforts are needed to investigate these singly heavy tetraquarks., Comment: 11 pages, 3 figures, comments and suggestions are welcome

Inspired by recent measurement of possible fully charmed tetraquarks in LHCb Collaboration, we investigate the mass spectra of fully heavy tetraquarks $QQ \bar Q \bar Q$ in an extended relativized quark model. Our estimations indicate that the broad structure around 6.4 GeV should contain one or more ground $cc \bar c \bar c$ tetraquark states, while the narrow structure near 6.9 GeV can be categorized as the first radial excitation of $cc \bar c \bar c$ system. Moreover, with the wave functions of the tetraquarks and mesons, the strong decays of tetraquarks into heavy quarkonium pair are qualitatively discussed, which can be further checked by the LHCb and CMS Collaborations., Comment: 7 pages, 3 figures, comments and suggestions are welcome

In the present work, the mass spectra of doubly heavy tetraquarks $T_{QQ^\prime}$ are systematically investigated in a relativized quark model. The four-body systems including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved within the variational method. Our results suggest that the $IJ^P=01^+$ $bb \bar u \bar d$ state is 54 MeV below the relevant $\bar B \bar B$ and $\bar B \bar B^*$ thresholds, which indicates that both strong and electromagnetic decays are forbidden, and thus this state can be a stable one. Its large hidden color component and small root mean square radius demonstrate that it is a compact tetraquark rather than a loosely bound molecule or point-like diquark-antidiquark structure. Our predictions of the doubly heavy tetraquarks may provide valuable information for future experimental searches., Comment: 13 pages, 7 figures, comments and suggestions are welcome

Recent lattice QCD calculations showed that a $d_{N\Omega}$ 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 $d_{N\Omega}$ state to its constituents and the decays into conventional hadrons, $d_{N\Omega} \to \Lambda \Xi$ and $d_{N\Omega} \to \Sigma \Xi$. Predictions for the sum of the decay rates are in the range of a few hundred keV. In addition, we find that the $d_{N\Omega} \to \Lambda \Xi$ mode is dominant, preferably searched for in a future RHIC experiment.

The $\rho$ 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 $\rho$ meson are explicitly given.

In the present work, we assign the newly observed $P_c(4312)$ as a $I(J^P)= \frac{1}{2} (\frac{1}{2})^-$ molecular state composed of $\Sigma_c \bar{D}$, while $P_c(4440)$ and $P_c(4457)$ as $\Sigma_c \bar{D}^\ast$ molecular states with $I(J^P)= \frac{1}{2} (\frac{1}{2})^-$ and $\frac{1}{2} (\frac{3}{2})^-$, respectively. In this molecular scenario, we investigate the $P_c\to J/\psi p$ process of these three states and further predict the ratios of the $\mathcal B(P_c\to J/\psi p)$ and those of $\mathcal B(\Lambda_b\to P_c K)$ between these three states, which could serve as a crucial test of the present molecular scenario., Comment: 6 pages, 5 figures

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

Recently, the BESIII Collaboration reported a new measurement of the $\eta_c \rho$ decay mode of $Z_c^{(\prime)}$, which motivated us to study the inner structure of $Z_c^{(\prime)}$ via investigating the hidden charm decays of these two $Z_c$ states. We consider the {triangle loop mechanism} contribution in the hidden charm decays of $Z_c^{(\prime)}$. Our estimations indicate that the triangle loop mechanism plays an important role in the decays of the $Z_c^{(\prime)}$, where our results are in agreement with the experimental observations in a reasonable parameter range. Furthermore, we point out that the $Z_c^{(\prime)}$ can be interpreted as the hadronic molecules, while the tetraquark scenario is less favored.

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 $\rho$ 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 $\rho$ meson based on a light-front constituent quark model.

Spin-1 hadrons have additional structure functions not present for spin 1/2 hadrons. These could probe novel aspects of hadron structure and QCD dynamics. For the deuteron, the tensor structure function $b_1$ inherently mixes quark and nuclear degrees of freedom. These proceedings discuss two standard convolution models applied to calculations of the deuteron $b_1$ structure functions. We find large differences with the existing HERMES data and other convolution model calculations. This leaves room for non-standard contributions to $b_1$ in the deuteron. We also discuss the influence of higher twist nuclear effects in the model calculations and data extraction at kinematics covered in HERMES and Jefferson Lab., Comment: Proceedings of 25th International Workshop on Deep Inelastic Scattering and Related Topics, 3-7 April 2017 University of Birmingham

We study $\rho$ 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 $\rho$ 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 $\rho$ meson.

The structure of $d^*(2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the $N-N$ scattering data and the binding energy of deuteron. The binding behavior of such a six quark system is solved by using a variational method. The trial wave function is chosen to be a combination of a basic spherical symmetric component of $[(0s)^6]_{orb}$ in the orbital space with $0\hbar\omega$ excitation and an inner structural deformation component of $[(0s)^5(1s)]_{orb}$ and $[(0s)^4(0p)^2]_{orb}$ in the orbital space with $2\hbar\omega$ excitation, both of which are in the spatial [6] symmetry. It is shown that the mass of the system is about $2356$ MeV, which is qualitative consistent with the result both from the two-cluster configuration calculation and from the data measured by the WASA Collaborations. This result tells us that as long as the medium-range interaction due to the chiral symmetry consideration is properly introduced, the mass of system will be reduced in a rather large extent. It also implies that the observed $d^*$ is a six-quark bound state with respect to the $\Delta\Delta$ threshold, which again supports the conclusion that $d^*$ is a hexaquark dominant state., Comment: 6 pages, 3 figures.

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., Comment: 4 pages, 2 eps figures, 22nd International Spin Symposium (Spin-2016), University of Illinois, Champaign, Illinois, USA, September 25-30, 2016

Tensor-polarized structure functions of a spin-1 hadron are additional observables which do not exist for the spin-1/2 nucleon. They could probe novel aspects of the internal hadron structure. Twist-2 tensor-polarized structure functions are $b_1$ and $b_2$, and they are related by the Callan-Gross-like relation in the Bjorken scaling limit. In this work, we theoretically calculate $b_1$ in the standard convolution description for the deuteron. Two different theoretical models, a basic convolution description and a virtual nucleon approximation, are used for calculating $b_1$ and their results are compared with the HERMES measurement. We found large differences between our theoretical results and the data. Although there is still room to improve by considering higher-twist effects and in the experimental extraction of $b_1$ from the spin asymmetry $A_{zz}$, there is a possibility that the large differences require physics beyond the standard deuteron model for their interpretation. Future $b_1$ studies could shed light on a new field of hadron physics. In particular, detailed experimental studies of $b_1$ will start soon at the Thomas Jefferson National Accelerator Facility. In addition, there are possibilities to investigate tensor-polarized parton distribution functions and $b_1$ at Fermi National Accelerator Laboratory and a future electron-ion collider. Therefore, further theoretical studies are needed for understanding the tensor structure of the spin-1 deuteron, including a new mechanism to explain the large differences between the current data and our theoretical results., Comment: 12 pages, 7 eps figures, 3 style files, typos are corrected as published in Phys. Rev. D 95, 074036 (2017)

We investigate the masses of $cs \bar c \bar s$ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential firstly, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schr\"{o}dinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of $X(4140)$ can be regarded as the $cs \bar c \bar s$ tetraquark ground states, and the $X(4700)$ can be assigned as the $2S$ excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of $X(4500)$ can be explained as the tetraquark composed of one $2S$ scalar diquark and one scalar antidiquark. In our approach, the $X(4274)$ cannot be explained as a tetraquark state, however, it can be a good candidate of the conventional $\chi_{c1}(3^3P_1)$ state. In addition, other charmonium-like states $\chi_{c0}(3915)$, $X(4350)$, $X(4630)$ and $X(4660)$, as the $cs \bar c \bar s$ tetraquark states, are also discussed., Comment: Minor changes, 8 pages, 2 figures

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.

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.

We study the masses of open charm and bottom tetraquark states within the diquark-antidiquark scenario in the relativized quark model proposed by Godfrey and Isgur. The diquark and antidiquark masses are firstly solved by relativized quark potential, and then treated as the usual antiquark and quark, respectively. The masses of tetraquark states are obtained by solving the Schr\"{o}dinger-type equation between the new diquark and antidiquark. We find the masses of $sq\bar b\bar q$ tetraquark configuration are much higher than that of $X(5568)$. This conclusion disfavors the possibility of $X(5568)$ as a tetraquark state within the diquark-antidiquark scenario. Further experimental searches are needed to clarify the nature of the signal observed by D0 collaboration., Comment: 5 pages, 1 figure, 2 tables. Version accepted by Phys. Rev. D

The structure of $d^*(2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the scattering and binding behaviors of baryonic systems. The mass and width are explicitly calculated with two types of trial wave functions. The result shows that the $(0s)^6 [6]_{orb}$ configuration is easy to convert to the configuration with the same $[6]_{orb}$ symmetry but $2\hbar \omega$ excitation back and forth, however, it is seldom to turn into a two-cluster configuration with a (1s) relative motion in between. The resultant mass and width are about $2394$MeV and $25$MeV, respectively, and the stable size is about $0.75fm$, which are consistent with both the results in the two-cluster configuration calculation and the data measured by the COSY collaboration. It seems that the observed $d^*$ is a six-quark dominated exotic state with a spherical shape and breath mode in the coordinate space. Moreover, if $d^*$ does have $2\hbar \omega$ excitation, the $d^* \to np\pi\pi\pi$ decay mode might be a good place to distinguish the real structure of the observed phenomenon by COSY. The masses of various isospin-spin states of six-light-quark systems are also computed. It is shown that by considering the coupling with the configurations with $2\hbar \omega$ excitations, only the mirror state with $IS$=$30$ will be lower down to the place where whose mass is slightly higher than the value of the $\Delta\Delta$ threshold., Comment: This paper has been withdrawn by the author as the further investigation is needed

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 investigate the neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $\pi^-p \to J/\psi n$ reaction within an effective Lagrangian approach. The background contributions for the process mainly come from $t$-channel $\pi$ and $\rho$ meson exchanges. The contributions of $P_c^0(4380)$ and $P_c^0(4450)$ states give clear peak structures in the magnitude of 1 $\mu$b at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral $P_c$ states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC., Comment: 9 pages, 6 figures. minor changes to text and added references

We study the radiative decays of the $Z_c(3900)^0$ in a hadronic molecule picture, where the $Z_c(3900)$ is treated as a $D \bar{D}^\ast +c.c$ hadronic molecule. The partial widths of $\Gamma(Z_c(3900)^0 \to \gamma \eta_c(2S))$ and $\Gamma(Z_c(3900)^0 \to \gamma \chi_{c0})$ are predicted to be of order 10 keV and the cross sections for $\sigma(e^+ e^- \to \pi^0 Z_c(3900) \to \pi^0 \gamma \eta_c(2S))$ and $\sigma(e^+ e^- \to \pi^0 Z_c(3900) \to \pi^0 \gamma \chi_{c0})$ are of order 0.1 pb at 4.23 GeV, which may be accessible for the BESIII and forthcoming BelleII., Comment: 8 pages, 11 figures, Phys.Rev.D version

We report on a theoretical study of the $\pi^- p \to D^- D^0 p$ reaction near threshold within an effective Lagrangian approach. The production process is described by $t$ channel $D^{*0}$ meson exchange, $s$-channel nucleon pole, and $u$ channel $\Sigma^{++}_{c}$ exchange. In our work, the final $D^0 p$ results from the ground $\Lambda^+_c(2286)$ state and also dominantly from the excited $\Lambda^+_c(2940)$ state which is assumed as a $D^{*0} p$ molecular state with spin parity $J^P = \frac{1}{2}^+$ or $\frac{1}{2}^-$. We calculate the total cross section of the $\pi^- p \to D^- D^0 p$ reaction. It is shown that the spin parity assignment of $\frac{1}{2}^-$ for $\Lambda^+_c(2940)$ gives a sizable enhancement for the total cross section in comparison with a choice of $J^p = \frac{1}{2}^+$. However, our theoretical result of the total cross section is sensitive to the value of the cutoff parameter involved in the form factor of the exchanged off-shell particles. Moreover, we also calculate the second order differential cross section and find it can be used to determine the parity of the $\Lambda^+_c(2940)$. It is expected that our model calculations can be tested by future experiments at J-PARC in Japan., Comment: Published version. Phys. Rev. D 92, 034029 (2015)

The analytical forms of the interaction potentials between one S-wave and one P-wave heavy mesons as well as the potentials between two P-wave heavy mesons are deduced based on a chiral quark model. Our results explicitly show the attractive property between two heavy mesons. Consequently, a series of possible molecular states are obtained. It is expected that our study might shed some light on the popular discussions of the newly observed XYZ states., Comment: arXiv admin note: substantial text overlap with arXiv:1206.0523

The role of Poincar\'e covariant space-time translations is investigated in the case of the pseudoscalar-meson charge form factors calculated within a relativistic quantum mechanics framework. It is shown that this role extends beyond the standard energy-momentum conservation, which is accounted for in all works based on this general approach. It implies constraints that have been largely ignored until now but should be nevertheless fulfilled to ensure the full Poincar\'e covariance. The violation of these constraints, which is more or less important depending on the form of relativistic quantum mechanics that is employed, points to the validity of using a single-particle current, which is generally assumed in calculations of form factors. In short, these constraints concern the relation of the momentum transferred to the constituents to the one transferred to the system, which most often differ in relativistic quantum mechanics while they are equal in field theory. How to account for the constraints, as well as restoring the equivalence of different relativistic quantum mechanics approaches in estimating form factors, is discussed. It is mentioned that the result so obtained can be identified to a dispersion-relation one. A short conclusion relative to the underlying dynamics is given in the pion case., Comment: 9 pages, 5 figures; published in the proceedings of LC2010, Light Cone 2010: Relativistic Hadronic and Particle Physics, Valencia : Spain (2010)

An effective potential in a meson-meson system is discussed based on the SU(3) chiral constituent quark model, and the analytic form of the potential is explicitly given. In addition, the effective potential is employed to study the bound state problem of $\omega\phi$, which is related to the new resonance of $f_0(1810)$ observed in BESII very recently., Comment: 7 pages, 4 figures

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

The role of Poincar\'e covariant space-time translations is investigated in the case of a relativistic quantum mechanics approach to the pion charge form factor. It is shown that the related constraints are generally inconsistent with the assumption of a single-particle current, which is most often referred to. The only exception is the front-form approach with $q^+=0$. How accounting for the related constraints, as well as restoring the equivalence of different RQM approaches in estimating form factors, is discussed. Some extensions of this work and, in particular, the relationship with a dispersion-relation approach, are presented. Conclusions relative to the underlying dynamics are given., Comment: 6 pages, 2 figures, proceedings of the QNP2009 international conference (Beijing, oct. 2009), to be published in Chinese Physics C

In a simple hadronic model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the $^3$He are estimated. The results show that the elastic contributions of two-photon exchange to the the single spin asymmetries for the nucleon are rather small while those for the $^3$He are relatively large. Besides the strong angular dependence, the two-photon contributions to the single spin asymmetry for the $^3$He are very sensitive to the momentum transfer., Comment: 11 pages, 8 figures

The corrections of two-photon exchange on deuteron electromagnetic form factors are estimated based on an effective Lagrangian approach. Numerical results for the form factors $G_{C,M,Q}$ of the deuteron with the corrections are compared to its empirical ones. Moreover, the two new form factors, due to the two-photon exchange, are analyzed. Possible way to test the two-photon exchange corrections to the deuteron form factors is discussed., Comment: 17 pages, 10 figures

Constraints related to transformations of currents under space-time translations have been considered for the relativistic quantum mechanics calculation of form factors of J=0 systems composed of scalar constituents with equal masses. Accounting for these constraints amounts to take into account many-body currents that restore the equality of the momentum transferred separately to the system and to the constituents, which holds in field-theory approaches but is not generally fulfilled in relativistic quantum mechanics ones. When this was done, discrepancies between results from different approaches could be found to vanish. The results are extended here to systems composed of spin-1/2 constituents with unequal masses. Moreover, as far as the equivalence of different approaches is concerned, some intermediate step could be skipped and the presentation of these results therefore slightly differs from the previous one. Due to the technical aspect of present results, this work is not aimed to be published but it could be useful for some applications like the form factors of the pion or kaon particles., Comment: 30 pages

We estimate the two-photon exchange corrections to both proton and neutron electromagnetic physical observables in a relativistic light cone quark model. At a fixed momentum transfer the corrections are found to be small in magnitudes, but with a strong angular dependence. Our results are comparable to those from simple hadronic model in a moderate momentum transfer region., Comment: 10 pages, 5 figures

Corrections of two-photon exchange to proton and neutron electromagnetic form factors are employed to study the effect of two-photon exchange on the deuteron electromagnetic form factors. Numerical results of the effect are given. It is suggested to test the effect in the measurement of $P_z$ in a small angle limit., Comment: 12 pages 9 figures

Two-photon annihilate contributions in the process $e^+ + e^- \to p + \bar{p}$ including $N$ and $\Delta$ 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 $\Delta(1232)$ contributions simultaneously, while the correction to $P_z$ is enhanced., Comment: 5 pages

Different relativistic quantum mechanics approaches have recently been used to calculate properties of various systems, form factors in particular. It is known that predictions, which most often rely on a single-particle current approximation, can lead to predictions with a very large range. It was shown that accounting for constraints related to space-time translations could considerably reduce this range. It is shown here that predictions can be made identical for a large range of cases. These ones include the following approaches: instant form, front form, and "point-form" in arbitrary momentum configurations and a dispersion-relation approach which can be considered as the approach which the other ones should converge to. This important result supposes both an implementation of the above constraints and an appropriate single-particle-like current. The change of variables that allows one to establish the equivalence of the approaches is given. Some points are illustrated with numerical results for the ground state of a system consisting of scalar particles., Comment: 37 pages, 7 figures; further comments in ps 16 and 19; further references; modified presentation of some formulas; corrected misprints

The general form of the cross section as well as the polarizations of electron-deuteron elastic scattering are given. Two-photon exchange effects are analyzed. Possible signatures of the two-photon exchange effects in the electron-deuteron elastic scattering are discussed., Comment: 15 pages

We use a diquark model of the nucleon to calculate the electromagnetic form factors of the nucleon described as a scalar and axialvector diquark bound state. We provide an analysis of the zero-mode contribution in the diquark model. We find there are zero-mode contributions to the form factors arising from the instantaneous part of the quark propagator, which cannot be neglected compared with the valence contribution but can be removed by the choice of wave function. We also find that the charge and magnetic radii and magnetic moment of the proton can be reproduced, while the magnetic moment of the neutron is too small. The dipole shape of the form factors, $G^p_M(Q^2)/\mu_p$ and $G^n_M(Q^2)/\mu_n,$ can be reproduced. The ratio $\mu G^p_E/G^p_M$ decreases with $Q^2,$ but too fast., Comment: 22 pages, 6 pages, accepted by J.Phys. G

The electromagnetic form factors, charge radii and decay constants of pion, K and K*(892) are calculated using the three forms of relativistic kinematics: instant form, point form and (light) front form. Simple representations of the mass operator together with single quark currents are employed with all the forms. Making use of previously fixed parameters, together with the constituent quark mass for the strange quark, a reasonable reproduction of the available data for form factors, charge radii and decay constants of pion, rho, K and K*(892) is obtained in front form. With instant form a similar description, but with a systematic underestimation of the vector meson decay constants is obtained using two different sets of parameters, one for pion and rho and another one for K and K*(892). Point form produces a poor description of the data., Comment: Accepted in Eur. Phys. Jour. A (2005)