| The structure of hadrons and strong interaction between hadrons are of particular interest within the field of particle and nuclear physics. Understanding the structure and dynamical origin of baryon resonances is one of the most important topics in hadron physics. Generally, the study is focused on the light quark system. In recent years, along with the continuous development of experiments, systems including heavy quarks also gradually arouses many interests[1]. In2003, BaBar collaboration reported strange charmed states DSJ(2317), DSJ(2460), which are difficult to fit in the conventional quark model. They have been considered to be the DK or D*K molecular state, tetraquarks or a mixture of them. Recently Belle group in KEK of Japan found state X(3872) in B meson decays, and then other new states Y(4260),Z(4430)[2]. The common feature of these states is that they all contain c and c in the final states of decays. Different explanations are proposed for their strange properties. For example, the charmonium, glueballs, molecular states, tetraquarks or a mixture of them. It is natural to expect to find reasonable explanations in the the fundamental theory of the strong interaction-Quantum chromodynamics (QCD).Quantum chromodynamics (QCD) has been believed to be the fundamental theory of the strong interaction, and it has been verified in the perturbative region. However, in the low energy region, it is hard to directly use QCD to study the complicated systems such as hadron-hadron interactions and exotic quark states due to the non-perturbative nature. Therefore, various QCD-inspired models have been developed and used to get physical insights of many phenomena of the hadronic world. The most convenient and widely used approach is the constituent quark model. The typical one is the chiral quark model(ChQM). To describe hadron-hadron interaction, σ meson is indispensable in various quark models. However the existence of σ meson is still in controversial. Although recent experiments have confirmed the existence of the σ meson which is identified as S-wave resonance of two π’s, but it can not introduce enough attraction in nucleon-nuclen(NN) interaction. Is there an alternative approach to the intermediate range attraction of NN interaction? It is an interest problem. Based on the conventional constituent quark model, which developed by Glashow-Isgur, the The quark delocalization color screening model (QDCSM) was developed in1990s by F. Wang et al. Applying to single hadron, it is just the Glashow-Isgur model, which the hadron properties can be described well. Ap-plying to NN interaction, the intermediate range attraction can be obtained without in-troducing a meson. The main advantages of QDCSM are that it enlarges the model space by introducing the quark delocalization, allows the multi-quark system to choose its most favorable configuration (by variation the energy of the system to delocalization parame-ter) through its own dynamics, and it takes into account of the differences of confinement interaction inside a single baryon and between two color singlet baryons, improving the model Hamiltonian. The model give a good description of NN, YN interactions and the properties of deuteron. Recent studies also showed that the intermediate-range attraction mechanism in QDCSM, quark delocalization and color screening is an alternative mech-anism other than the σ-meson exchange in ChQM. These models have been successfully applied to the study of light-quark system, here we extend the two models to the systems which including c quark.In the conventional quark model, baryons are ascribed into3-quark (qqq) con-figuration, the ground-state baryons are successfully described as the octet baryons (spin=1/2) and the decuplet baryons(spin=3/2). But the constituent quark models does not give a definite picture of the structures of the excited baryon states, such as N(1440), N*(1535),N*(1650), N*(1700),A(1405) etc. Thus it is still confusing to us whether the baryon resonances should be described by three-quark (qqq) or five-quark configurations (qqqqq), or baryon-meson dynamically generated states, or a mixture of them. One of the difficulty to pin down the nature of these baryon resonances is that these states are in the same energy region. There are always some adjustable parameters in each model to fit the experimental data. In order to avoid this difficult, we study the baryon states with heavy quark:Ncc*,λcc*etc.. Their masses are above4GeV. If these states exist, they can be looked for at the forthcoming PANDA/FAIR experiments. Be-cause of their high energy, they definitely cannot be accommodated by quark models with three light constituent quarks. Such a high-energy resonance, if it exists, can only be dominated by a hidden charm five-constituent-quark configuration (qqqcc).A systematic search of excited baryon states with cc components are performed in the framework of resonanting-group method calculation is done by using QDCSM and ChQM (Salamenca version). Several candidates are proposed. First, we want to find out what is the general features, and try to provide more reliable results. Sec-ondly, by comparing all the results from different models, we show again the equiv-alence of the two models in the intermediate-range attraction mechanism. Thirdly, we will determine the suitability of the two models when extended to SU(4). By fit-ting the experimental masses of charmed baryons (Σc, Λc, Ξc, Ωc) and charmed mesons (D,D*,Ds,D*,ηc,J/ψ), the model parameters are fixed. To deal with the charmed hadrons, D, Ds, ηc meson exchange potentials are included in the calculation. Then the models are applied to the study of five-quark systems with charm quarks. The adia-batic approximation and dynamics calculation are all done. In summary, we find five bound states:SIJ=-2,1/2,1/2, SIJ=-2,1/2,3/2, SIJ=-3,0,1/2, SIJ=-3,0,3/2and SI J=-3,0,5/2。The binding energies are much lower than the corresponding light-quark systems. The largest binding energy is about lOMeV. The phenomenon is related to the intermediate-range attraction mechanism. Our results show that Ec-D is a bound state and Λc-D has a repulsive interaction and thus is unbound. This result is agreement with that of Z. Y. Zhang’s work. Furthermore we find more possible bound states due to the systematic search. |
PDF Full Text Request