Inspired by the discovery of the dibaryon $d^{*}$ and the experimental search of $NΩ$ dibaryon with the STAR data, we study the strange dibaryon $NΩ$ further in the framework of quark delocalization color screening model and chiral quark model. We have shown $NΩ$ is a narrow resonance in $ΛΞ$ D-wave scattering before. However, the $Λ$-$Ξ$ scattering data analysis is quite complicated. Here we calculate the low-energy $NΩ$ scattering phase shifts, scattering length, effective range and binding energy to provide another approach of STAR data analysis. Our results show there exists an $NΩ$ "bound" state, which can be observed by the $N$-$Ω$ correlation analysis with RHIC and LHC data, or by the new developed automatic scanning system at J-PARC. Besides, we also find that the hidden color channel-coupling is important for the $NΩ$ system to develop intermediate-range attraction.
We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with $I=\frac{1}{2}$. We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible SU(3) flavor state. Second, we consider the states composed of five light quarks, and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using variational method in a constituent quark…
We perform a coupled--channel calculation of the H dibaryon within a chiral constituent quark model. The problem is solved within a quark model constrained by the experimental data of strangeness --1 and --2 two--baryon systems. We examine in detail the role played by the different contributions of the interacting potential as well as the number of coupled channels considered. Special attention has been payed to the parameter dependence, flavor symmetry breaking and spatial configurations. The value extracted for the binding energy of the H dibaryon, being compatible with the restrictions impo…
We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with S=0 in both the flavor SU(3) symmetric and breaking cases. We discuss how the color $\otimes$ isospin $\otimes$ spin states of dibaryon in the symmetry broking case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons are then discussed, by using the variational method within a constituent quark model with a confining and color-spin interactions. To compare our resu…
The most strange dibaryon $ΩΩ$ with quantum numbers $S=-6$, $I=0$, and $J^{P}=0^{+},~1^{-},~2^{+},~3^{-}$ is reanalyzed in the framework of quark delocalization color screening model (QDCSM) and chiral quark model (ChQM). The $ΩΩ$ dibaryon with $J^{P}=0^{+}$ is bound, and the one with other quantum numbers $J^{P}=1^{-},~2^{+},~3^{-}$ are all unbound in our calculation. The low-energy scattering phase shifts, the scattering length, and the effective range of the $ΩΩ$ dibaryon with $J^{P}=0^{+}$ also support the existence of such strange dibaryon. This dibaryon is showed to be a shallow bound st…
We investigate the properties of dibaryons containing u and d quarks in the constituent quark model. In constructing the ground state wave function, we choose the spatial part to be fully symmetric and the remaining color, isospin and spin part to be antisymmetric so as to satisfy the the Pauli principle. By adapting the IS coupling scheme that combine the isospin basis function with the spin basis function, and subsequently coupling this to the color singlet basis function, we construct the color $\otimes$ isospin $\otimes$ spin states compatible with the physical states of the dibaryon. By u…
We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems on a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation provides also information about anticharmed pentaquarks that are seemingly unbound in simple quark models.
The recent observation of a hadronic resonance $d^*$ in the proton-neutron system with isospin $I = 0$ and spin-parity $J^P = 3^+$ raises the possibility of producing other novel six-quark dibaryon configurations allowed by QCD. A dramatic example of an exotic six-quark color-singlet system is the charge $Q=+4$, isospin I=3, $I^z=+3$ $|uuuuuu>$ state which couples strongly to $Δ^{++}$ + $Δ^{++} .$ The width and decay properties of such six-quark resonances could be regarded as manifestations of "hidden-color" six-quark configurations, a first-principle prediction of QCD -- SU(3)-color gauge th…
The d' dibaryon in the quark-delocalization, color-screening model
在夸克离域色屏蔽模型（QDCSM）下研究了提出的$d' (IJ^P=00^-)$重子的存在性和质量问题。物理基和对称基之间的变换被推广到SU（2）轨道对称性以外的情形。利用由重子性质和$NN$散射确定的参数，我们发现在$IJ^P=00^-$通道中存在一个温和的吸引，但它并不强到足以形成$d'$态的深度束缚态.（同位旋）I=2 N $Δ$构型也没有深度束缚态。这些结果表明，如果窄的双重子$d'$态确实存在，那么它一定具有更复杂的结构。
Possible $NΩ$-like dibaryons $NΩ_{ccc}$ and $NΩ_{bbb}$ with quantum numbers $IJ^P=\frac{1}{2}2^+$ are investigated within the framework of quark delocalization color screening model. We find both of these two states are bound, and the binding energy increases as the quarks of the system become heavier. The attraction between $N$ and $Ω_{ccc}$ (or $Ω_{bbb}$) mainly comes from the kinetic energy term due to quark delocalization and color screening. The effect of the channel-coupling provides more effective attraction to $NΩ_{ccc}$ and $NΩ_{bbb}$ systems. Besides, the scattering length, the effec…
We perform a systemical investigation of the low-lying doubly-heavy dibaryon systems with strange $S=0$, isospin $I=0$, $1$, $2$ and the angular momentum $J=0$, $1$, $2$, $3$ in the quark delocalization color screening model. We find the effect of channel-coupling cannot be neglected in the study of the multi-quark systems. Due to the heavy flavor symmetry, the results of the doubly-charm and doubly-bottom dibaryon systems are similar with each other. Both of them have three bound states, the quantum numbers of which are $IJ=00$, $IJ=02$ and $IJ=13$, respectively. The energies are $4554$ MeV, …
Charmed dibaryon states with the spin-parity $J^π=0^+$, $1^+$, and $2^+$are predicted for the two-body $Y_cN$ ($=Λ_c$, $Σ_c$, or $Σ^*_c$) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the $Y_cN$-CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the $Σ_c N$ and $Σ^*_c N$ thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_c N$ resonance states in the heavy quark limit, where t…
We study the quark mass dependence of the H-dibaryon in the strangeness $S=-2$ baryon-baryon scattering. A low-energy effective field theory is used to describe the coupled-channel scattering, in which the quark mass dependence is incorporated so as to reproduce the lattice QCD data by the HAL QCD collaboration in the SU(3) limit. We point out the existence of the Castillejo-Dalitz-Dyson (CDD) pole in the $ΛΛ$ scattering amplitude below the threshold in the SU(3) limit, which may cause the Ramsauer-Townsend effect near the $NΞ$ threshold at the physical point. The H-dibaryon is unbound at the …
We study the two-baryon system with two units of charm looking for the possible existence of a loosely bound state resembling the $H$ dibaryon. We make use of a chiral constituent quark model tuned in the description of the baryon and meson spectra as well as the $NN$ interaction. The presence of the heavy quarks makes the interaction simpler than in light baryon systems. We analyze possible quark-Pauli effects that would be present in spin-isospin saturated channels. Our results point to the non-existence of a charmed $H$-like dibaryon, although it may appear as a resonance above the $Λ_cΛ_c$…
The existence of full heavy dibaryons $Ω_{ccc}Ω_{bbb}$, $Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}$ with $J=0,~1,~2,~3$ and $P=\pm1$ are investigated in the framework of a constituent quark model. The dibaryon composed of six $c$ or $b$ quarks with $J^{P}=0^{+}$ is possible to be bound, while the dibaryon with the $cccbbb$ configuration is difficult to form any bound state. We also study the interaction between two full heavy baryons, and the effective potentials, suggesting the existence of dibaryons $Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}$, and the absence of binding for $Ω_{ccc}Ω_{bbb}$ system. Besi…
Possible $H$-like dibaryon states $Λ_{c}Λ_{c}$ and $Λ_{b}Λ_{b}$ are investigated within the framework of quark delocalization color screening model. The results show that the interaction between two $Λ_{c}$'s is repulsive, so it cannot be bound state by itself. However, the strong attraction in $Σ_{c}Σ_{c}$ and $Σ^{*}_{c}Σ^{*}_{c}$ channels and the strong channel coupling, due to the central interaction of one-gluon-exchange and one-pion-exchange, among $Λ_{c}Λ_{c}$, $Σ_{c}Σ_{c}$ and $Σ^{*}_{c}Σ^{*}_{c}$ push the energy of system below the threshold of $Λ_{c}Λ_{c}$ by $22$ MeV. The correspondi…
Diquark models have been applied with varying degree of success to tetraquark and pentaquark states involving both light and heavy quark degrees of freedom. We discuss the applicability of such models to light quark dibaryons, viewed as three-diquark objects. Highlighting the case of the d*(2380) dibaryon resonance, we demonstrate the inapplicability of diquark models in the light quark sector.
The dibaryon concept for the nuclear force is presented, assuming that the main attraction between the nucleons at medium distances is determined by the $s$-channel exchange of an intermediate six-quark (dibaryon) state. To construct the respective $NN$ interaction model, a microscopic six-quark description of the $NN$ system is used, in which symmetry aspects play a special role. It is shown that the $NN$ interaction in all important partial waves can be described properly by a superposition of the long-range $t$-channel one-pion exchange and the $s$-channel exchange by an intermediate dibary…
The H-dibaryon is the exotic multiquark state with baryon number 2 and strangeness $-2$. The existence of the deeply bound H-dibaryon is excluded by the observation of the double hypernuclei. However the recent Lattice QCD simulations have found the bound state below the $ΛΛ$ threshold with large quark masses by HALQCD and NPLQCD collaborations. In this talk, the quark mass dependence of the H-dibaryon mass is discussed using the pionless effective field theory (EFT) where a bare H-dibaryon field is coupled with two-baryon states. We determine the parameters in this theory by fitting the recen…
We explore the possibility of very heavy dibaryons with three charm quarks and three beauty quarks, $bbbccc$, using a constituent model which should drive to the correct solution in the limit of hadrons made of heavy quarks. The six-body problem is treated rigorously, in particular taking into account the orbital, color and spin mixed-symmetry components of the wave function. Unlike a recent claim based on lattice QCD, no bound state is found below the lowest dissociation threshold.
We discuss the possible existence of exotic dibaryons with a heavy antiquark, being realized three-body systems, Dbar^(*)NN and B^(*)NN. These are genuinely exotic states with no quark-antiquark annihilation. We consider the heavy quark spin and chiral symmetries, and introduce the one pion exchange potential between a Dbar^(*) (B^(*)) meson and a nucleon N. As for the NN interaction, we employ the Argonne v^\prime_8 potential. By solving the coupled-channel equations for PNN and P^* NN (P^(*)=Dbar^(*) and B^(*)), we find bound states for (I,J^P)=(1/2,0^-) as well as resonant states for (I,J^P…
In this contribution, dedicated to the memory of Walter Greiner, we discuss the structure and width of the recently established d*(2380) dibaryon, confronting the consequences of our Pion Assisted Dibaryons hadronic model with those of quark motivated calculations. In particular, its relatively small width of about 70 MeV favors hadronic structure for the d*(2380) dibaryon rather than a six-quark structure.
We perform a dynamical calculation of the $ΔΔ$ dibaryon candidates with $IJ^{P}=03^{+}$ and $IJ^{P}=30^{+}$ in the framework of two constituent quark models: the quark delocalization color screening model and the chiral quark model. Our results show that the dibaryon resonances with $IJ^{P}=03^{+}$ and $IJ^{P}=30^{+}$ can be formed in both models. The mass and width of $IJ^{P}=03^{+}$ state are smaller than that of $IJ^{P}=30^{+}$ state due to the one-gluon-exchange interaction between quarks. The resonance mass and decay width of $IJ^{P}=03^{+}$ state in both models agree with that of the rec…
在微观夸克壳模型中，用单夸克跃迁算符描述q -> pi + q '，研究了d' -> pi + N + N过程中d '-双重子的介子衰变.对于d'，量子数J^P=0^-，T=0，我们采用了一个六夸克壳模型波函数，其空间组态为s^5p [51]_X，谐振子量子数为N=1。结果表明，介子衰变宽度强烈依赖于d '的质量和大小。在d'质量的计算值与实验值接近的情况下，得到了0.04MeV的小的介子衰变宽度。这是一个数量级小于实验建议的值0.5兆电子伏。提出了两种改进计算宽度的可能性。文中还讨论了跃迁算子中非静校正项的作用以及衰变顶点处的形状因子对衰变宽度的影响。
There are encouraging evidences for registration of excitations of quark oscillator levels in compressed 2-nucleon systems, which were hidden in two independently published experimental works for many years. Data obtained by EVA collaboration can be considered as the third possible confirmation of this conjecture. Moreover, they drop hints about existence of coherent dibaryons which may be interpreted as usual or generalized coherent states of the oscillator. These data may also be an explicit example of a physical process described by Landau and Peierls in their reasoning concerning the energ…
基于各种夸克模型计算，讨论了最近发现的五夸克态。理论上不能排除态的奇宇称，因为与非平凡色结构有关的贡献还没有完全研究。其他多夸克态，特别是二重子，也被讨论。一个奇异的-3 N $Ω$重子已经被证明具有小到12-22 keV的宽度，并且应该在$Ω$高生产率反应中被检测到，例如在RHIC，COMPAS和计划中的JHF和FAIR计划中。
We present results of the first lattice QCD calculation of three-flavored heavy dibaryons both in the flavor-symmetric and antisymmetric channels. These dibaryons have spin zero, and are constructed using various possible combinations of quark flavors with at least one of them as the charm or the bottom quark, i.e., namely, $H_c(cudcud), H_b(budbud), H_{bcs}(bcsbcs)$, $H_{csl}(cslcsl), H_{bsl}(bslbsl)$ and $H_{bcl}(bclbcl)$; $l\in u,d$. We compute the ground state masses of these dibaryons and the calculations are performed on three $N_f=2+1+1$ HISQ gauge ensembles of the MILC collaboration, w…
Inspired by the experimental report by WASA-at-COSY Collaboration, we investigate the possibile existence of the dibaryon candidate $NΔ$ with quantum numbers $IJ^P=21^+$ ($D_{21}$). The dynamical calculation shows that we cannot obtain the bound $D_{21}$ state in the models which can obtain the experimental $d^{*}$. %although the $D_{21}$ state can bound in the range of parameters in quark models. The low-energy scattering phase shifts of the $N-Δ$ scattering give the same conclusion. Besides, the mass calculation by using the Gursey-Radicati mass formula and the analysis of the matrix element…
In the present work, we construct eight six-quark currents to study the $Σ_c\barΣ_c$ baryonium and $Σ_cΣ_c$ dibaryon states via the QCD sum rules. For either $Σ_c\barΣ_c$ baryonium or $Σ_cΣ_c$ dibaryon states, we construct four currents with the $J^P=1^-, 1^+, 0^+$ and $0^-$. Except the current $1^+$ of $Σ_cΣ_c$, we find the Borel windows for the other seven. There are two possible $Σ_c\barΣ_c$ molecular states or compact six-quark states with the $J^P=1^-$ and $0^-$. The results of the current $0^+$ of $Σ_cΣ_c$ show a possible $Σ_cΣ_c$ molecular state with $20$ MeV binding energy. We find two…
We present a first study on a pair of triply charmed baryons, $Ω_{ccc}Ω_{ccc}$ in the $^1S_0$ channel, on the basis of the HAL QCD method. The measurements are perfomed on the $(2+1)$-flavor lattice QCD configurations with nearly physical light-quark masses and physical charm-quark mass. We show that the system with the Coulomb repulsion taking into account the charge form factor of $Ω_{ccc}$ leads to the scattering length $a^\mathrm{C}_0\simeq-19$ fm and the effective range $r^\mathrm{C}_\mathrm{eff}\simeq0.45$ fm, which indicates $Ω_{ccc}Ω_{ccc}$ is located in the unitary regime.
Hexaquarks constitute a natural extension of complex quark systems like also tetra- and pentaquarks do. To this end the current status of $d^*(2380)$ in both experiment and theory is shortly reviewed. Recent high-precision measurements in the nucleon-nucleon channel and analyses thereof have established $d^*(2380)$ as an indisputable resonance in the long-sought dibaryon channel. Important features of this $I(J^P) = 0(3^+)$ state are its narrow width and its deep binding relative to the $Δ(1232)Δ(1232)$ threshold. Its decay branchings favor theoretical calculations predicting a compact hexaqua…
A number of charmonium- and bottomonium-like meson states have been observed that have properties that do not match well to expectations for the simple quark-antiquark substructure suggested by the constituent quark model. Some of them are electrically charged and decay to final states containing hidden charmonum or bottomonium mesons and, thus, must contain at least four quarks. Common properties of these so-called XYZ mesons are partial widths for decays to hidden quarkonium states plus light hadrons that are much larger than corresponding partial widths for established quarkonium mesons. I …
We report the first lattice quantum chromodynamics (QCD) study of deuteron($np$)-like dibaryons with heavy quark flavours. These include particles with following dibaryon structures and valence quark contents: $Σ_cΞ_{cc} (uucucc)$, $Ω_cΩ_{cc} (sscscc)$, $Σ_bΞ_{bb} (uububb)$, $Ω_bΩ_{bb} (ssbsbb)$ and $Ω_{ccb}Ω_{cbb} (ccbcbb)$, and with spin ($J$)-parity ($P$), $J^{P} \equiv 1^{+}$. Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons $Ω_cΩ_{cc} (sscscc)$, $Ω_bΩ_{bb} (ssbsbb)$ and $Ω_{ccb}Ω…
A pair of triply charmed baryons, $Ω_{ccc}Ω_{ccc}$, is studied as an ideal dibaryon system by (2+1)-flavor lattice QCD with nearly physical light-quark masses and the relativistic heavy quark action with the physical charm quark mass. The spatial baryon-baryon correlation is related to their scattering parameters on the basis of the HAL QCD method. The $Ω_{ccc}Ω_{ccc}$ in the ${^1S_0}$ channel taking into account the Coulomb repulsion with the charge form factor of $Ω_{ccc}$ leads to the scattering length $a^{\rm C}_0\simeq -19~\text{fm}$ and the effective range $r^{\rm C}_{\mathrm{eff}}\simeq…
