Search

We investigate the $P$-wave states $T^-_{bb}$ in the isospin singlet and three excited modes [excitation occurring in the diquark $[bb]^{s_1}_{c_1}$ ($\rho $-mode), antidiquark $[\bar{u}\bar{d}]^{s_2}_{c_2}$ ($r$-mode) or between them ($\lambda$-mode)] from diquarks in a quark model. We analyze the dynamical behaviors of the diquark $[bb]^{s_1}_{c_1}$, antidiquark $[\bar{u}\bar{d}]^{s_2}_{c_2}$ and their correlations in the states $T^-_{bb}$ by decomposing the interactions from various sources in the model. The absolute dominant color-spin configuration, more than $99\%$, in the $\rho$-mode with $1^1P_1$ is $[bb]^0_{\bar{\mathbf{3}}}[\bar{u}\bar{d}]^0_{\mathbf{3}}$. Its energy is lower by about $18$ MeV than the threshold $\bar{B}\bar{B}$ so that it can establish a compact bound state. The chromomagnetic and meson-exchange interactions in the antidiquark $[\bar{u}\bar{d}]^0_{\mathbf{3}}$ are responsible for its binding mechanism. Two other excited modes are higher than their respective threshold. The color configuration $\mathbf{6}\otimes\bar{\mathbf{6}}$ need to be handled discreetly in the tetraquark states., Comment: 7 pages, 1 figures, 4 tables, to be published in Phys. Rev. D

We reveal the quark exchange effects related to both the kinetic energy and various interactions in the single flavored dibaryon bound states with $^1S_0$ in the quark models. The hadron covalent bond can be established by the shared identical quarks due to the quark exchange effect between two colorless baryons. Such hadron covalent bond plays a decisive role in the deuteronlike di-$\Omega_{ccc}$ and di-$\Omega_{bbb}$ covalent molecule states. The $\sigma$-meson exchange is indispensable in the deuteronlike di-$\Delta^{++}$ and compact di-$\Omega$ states. The hadron covalent bond clearly appears in the di-$\Delta^{++}$ state but is hidden in the di-$\Omega$ state. The chromomagnetic interaction is always repulsive in the di-$\Delta^{++}$, di-$\Omega$, di-$\Omega_{ccc}$, and di-$\Omega_{bbb}$ states. The color-electric interaction is strongly attractive in the di-$\Omega$ state but weakly attractive or repulsive in the di-$\Delta^{++}$, di-$\Omega_{ccc}$, and di-$\Omega_{bbb}$ states., Comment: 7 pages, 4 tables

Here we study the quark orbital angular momentum of the ground octet baryons employing an extended chiral constituent quark model, within which the baryon wave functions are taken to be superposition of the traditional $qqq$ and the $qqqq\bar{q}$ higher Fock components. Coupling between the two configurations is estimated using the $^3P_{0}$ quark-antiquark creation mechanism, and the corresponding coupling strength is determined by fitting the sea flavor asymmetry of the nucleon. The obtained numerical results show that the quark angular momentum of the nucleon, $\Sigma$, $\Lambda$ and $\Xi$ hyperons are in the range $0.10$-$0.30$. In addition, the quark angular momentum of all the hyperons are a little bit smaller than that of the nucleon. And the octet baryons spin fractions taken by the intrinsic quark orbital angular momentum could be up to $60\%$ in present model., Comment: 9 pages, 3 figures, 3 tables

Inspired by the states $T_{cs0}(2900)^0$, $T_{cs1}(2900)^0$, $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ reported by the LHCb Collaboration, we carry out a systematical investigation on the properties of the ground and $P$-wave states $[cs][\bar{u}\bar{d}]$ and $[cu][\bar{s}\bar{d}]$ with various spin, isospin or $U$-spin, and color combinations in a multiquark color flux-tube model. Matching our results with the spin-parity and mass of the states $T_{cs0}(2900)^0$ and $T_{cs1}(2900)^0$, we can describe them as the compact states $[cs][\bar{u}\bar{d}]$ with $I(J^{P})=1(0^+)$ and $0(1^-)$ in the model, respectively. The ground state $T_{cs0}(2900)^0$ is mainly made of strongly overlapped an axial-vector $[cs]_{\bar{\mathbf{3}}_c}$ and an axial-vector $[\bar{u}\bar{d}]_{\mathbf{3}_c}$. The $P$-wave state $T_{cs1}(2900)^0$ is dominantly consisted of a gradually separated scalar or axial vector $[cs]_{\bar{\mathbf{3}}_c}$ and a scalar $[\bar{u}\bar{d}]_{\mathbf{3}_c}$ in the shape of a dumbbell. Supposing the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ belong to the same isospin triplet, the mass of the state $\left [[cu]_{\bar{\mathbf{3}}_c}[\bar{s}\bar{d}]_ {\mathbf{3}_c}\right ]_{\mathbf{1}_c}$ with symmetrical $U$-spin and $J^P=0^+$ is highly consistent with that of the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$ in the model. After coupling two color configurations, the state $[cu][\bar{s}\bar{d}]$ is slightly lighter than the states $T^a_{c\bar{s}0}(2900)^{0}$ and $T^a_{c\bar{s}0}(2900)^{++}$. In addition, we also discuss the properties of other states in the model., Comment: 9 pages, 4 tables, comments are welcome

In present work, spectrum of the $S$-wave fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q=c,b$), i.e., $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$, $bc\bar{c}\bar{c}$/ $cc\bar{b}\bar{c}$, $bb\bar{c}\bar{b}$/$cb\bar{b}\bar{b}$, and $bc\bar{b}\bar{c}$ are systematically investigated within an nonrelativistic constituent quark model, in which the Instanton-induced and one-gluon-exchange interactions are taken into account as the residual spin-dependent hyperfine interaction. Our results show that the states with $cc\bar{c}\bar{c}$ and $bb\bar{b}\bar{b}$ components could be located around $ 6500$ MeV and $ 19200$ MeV, respectively. Based on our calculations, the new $X(6900)$ state observed by LHCb may be not a ground $cc\bar{c}\bar{c}$ tetraquark state, while it could be an orbitally or radially excited state of $cc\bar{c}\bar{c}$ system. On the other hand, the recently reported $X(6600)$ state by CMS and ATLAS can be explained as a ground $cc\bar{c}\bar{c}$ tetraquark state with spin-parity $J^{PC} =0^{++}$., Comment: Version to appear in Eur. Phys. J. C

We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\bar{q}) (q=u, d, s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}P_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the singlet axial charges of the octet baryons, which should indicate total baryons spin arising from the spin of the quarks, fall in the range $0.45-0.75$ in present model. This is in consistent with the predictions by lattice QCD and chiral perturbation theory. It's also very interesting that the light quarks spin $\Delta u$ and $\Delta d$ in the $\Lambda$ baryon are of small but negative values, which exactly vanish in the traditional three-quark model., Comment: Submitted to Phys. Rev. C. arXiv admin note: text overlap with arXiv:2106.00866

Spectrum of the low-lying hidden- and double-charm tetraquark states are investigated in a nonrelativistic quark potential model, where the Instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. The model parameters are fixed by fitting the spectrum of the ground hadron states. Our numerical results show that masses of several presently studied tetraquark states are close to those of the experimentally observed candidates of exotic meson, which indicates that the corresponding compact tetraquark components may take considerable probabilities in those observed exotic states., Comment: Version to appear in Eur. Phys. J. C

We analyse the deuteron-like $T^+_{cc}$ state observed by the LHCb Collaboration from the perspective of the quark clustering. The $T^+_{cc}$ state implies the possible existence of other compact doubly heavy tetraquark states., Comment: 4 pages, 3 tables, comments are welcome

We make an exhaustive investigation on the pentaquark states $qqqc\bar{c}$ ($q=u, d$ and $s$) and discuss the effect of color structures in a multiquark color flux-tube model. We exhibit a novel picture of the structure and properties of the states $P_c$ and $P_{cs}$ observed by the LHCb Collaboration. We can describe the states as the compact pentaquark states in the model. The spin-parity of the group of $P_c(4312)^+$ and $P_c(4337)^+$ is $\frac{1}{2}^-$ while that of the group of $P_c(4380)^+$, $P_c(4440)^+$ and $P_c(4457)^+$ is $\frac{3}{2}^-$. Their structures are pentagon, diquark, pentagon, diquark, and octet, respectively. The members in each group can be analogically called QCD isomers because of their the same spin-parity and quark content but different color structures. The singlet $P_{cs}(4459)^0$ has pentagon structure and spin-parity of $\frac{1}{2}^-$. In addition, we also predict the $P_{cs}$, $P_{c ss}$ and $P_{csss}$ families in the model. The five-body confinement potential based on the color flux-tube picture, which is a collective degree of freedom and induces QCD isomer phenomenon, plays an important role in the formation of the compact states., Comment: 10 pages, 2 figures, 6 tables, comments are welcome

Spectrum of the low-lying $\Omega_{cc}$ resonances with negative parity, which are assumed to be dominated by $sccq\bar{q}$ pentaquark components, is investigated using the chiral constituent quark model. Energies of the $\Omega_{cc}$ resonances are obtained by considering the hyperfine interaction between quarks by exchanging Goldstone boson. Possible $sccq\bar{q}$ configurations with spin-parity $1/2^{-}$, $3/2^{-}$ and $5/2^{-}$ are taken into account. Numerical results show that the lowest $\Omega_{cc}$ resonances with negative parity may lie at $4050 \pm 100$ MeV. In addition, the transitions of the $\Omega_{cc}$ resonance to a pseudoscalar meson and a ground baryon state are also investigated within the chiral Lagrangian approach. We expect that these $\Omega_{cc}$ resonances could be observed in the $\bar{D}\Xi_{c}$ channel by future experiments., Comment: typos corrected