[en] The possibility of QQ q-bar q-bar heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q is the light quark (u, d, or s). We obtain a bound state for the bb n-bar n-bar configuration with quantum number J^P = 1⁺, I = 0 and for the cc n-bar n-bar (J^P = 1⁺, I = 0) configuration, which is not bound but slightly above the D*D* threshold (n is u or d quark). Meanwhile, we also conclude that a weakly bound state in bb n-bar n-bar system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions

[en] A discussion is presented of the estimates of the energy and width of resonances in constituent models, with focus on the tetraquark states containing heavy quarks. (author)

[en] Progress on Quark-Gluon Plasma (QGP)

[en] We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where u, d masses were neglected and first order interactions were taken into account. We find that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1-2 order of magnitude as compared to earlier results. Also the damping time is 2-3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations. (author)

[en] In the past decade, a lot of new hadrons containing heavy quarks were discovered which do not fit into the scheme provided by the traditional quark models. Such states are known as the XYZ states and they are conventionally referred to as exotic ones. At present, there is no consensus on their nature, and different models and approaches have been suggested to explain their unusual properties. The talk is devoted to a brief overview of the molecule model for such exotic states.

[en] The mass spectrum of heavy baryons is calculated as nonrelativistic bound states of three quarks, using phenomenological potentials for the quark-quark interactions derived from QQ-bar effective potentials obtained from fits of the J/psi and GAMMA families. The Schroedinger's equation is solved according to Fluegge and Zickendraht's prescription, using a method developed especially for confining potentials. Results are compared for several types of confining potentials

[en] I develop an extension of the usual three-flavor quark model to four flavors ( u, d, s and c ), and discuss the classification of pentaquark states with hidden charm. This work is motivated by the recent observation of such states by the LHCb Collatoration at CERN. (paper)

[en] Understanding the quark composition of hadrons has been a central goal in nonperturbative quantum chromodynamics for decades. Standard hadrons are tradition ally classified based on the quark model, with baryons consisting of three quarks (qqq) and mesons formed from a quark–antiquark pair (qq¯) While many established states align with this quark model, there are certain hadrons, including observed resonances, whose properties suggest an exotic structure, featuring unconventional configurations. In the case of light scalar mesons, their conventional quark content remains a subject of ongoing investigation, with many theoretical interpretations concerning whether their internal structure conforms to compact multiquark states or exhibits a more molecular-like configuration. Recently, the ALICE experiment has conducted estimations of the nuclear modification factor for the f₀(980) in p-Pb collisions. The results are shown in the article and reveal a significant f₀(980) yield suppression at low p_T, which is stronger than that measured for charged hadrons and is more pronounced for more central collisions. This suppression may be attributed to the presence of rescattering effects. Interestingly, there is no Cronin peak observed in the intermediate p_T region, which might suggest that the f₀(980) meson possess an ordinary meson structure

[en] Conventionally, it is claimed that hexaquarks are exotic particles, most of which have not yet been experimentally detected. This essay is fixated on the view to extend a simple phenomenological model based on the Gürsey-Radicati mass formula for hadrons, including charm baryons and to predict the mass of hexaquark states. To make our purpose conspicuous, we perform a numerical tuning of this model, consisting of four sets, each containing six free parameters for baryons and dibaryons. In the long run, other predicted values for the mass of additional hexaquarks could be shown to agree with upcoming experimental results. As we have asserted, the results obtained from this work give us a deeper insight into the structural features of six-quark particles. Finally, we have included other available data from the other works and compared that data with ours. (author)

[en] We perform the first study for the heavy-heavy-light quark (QQq) potential in SU(3) quenched lattice QCD with the Coulomb gauge. The calculations are done with the standard gauge and O(a)-improved Wilson fermion action on the 16⁴ lattice at β=6.0. We calculate the energy of QQq systems as the function of the distance R between the two heavy quarks, and find that the QQq potential is well described with a Coulomb plus linear potential form up to the intermediate distance R≤0.8 fm. Compared to the static three-quark case, the effective string tension between the heavy quarks is significantly reduced by the finite-mass valence quark effect. This reduction is considered to be a general property for baryons