The Study Of Spectra And Structures Of Multi-Quarks

Since X(3872)was reported by Belle collaborations in 2003,many exotic hadron states were discovered in experiment.Since it do not fit into the picture of conventional hadrons,they are called "exotic hadrons".Multi quarks are one the main interpret of exotic hadrons.They are consist of more than three quarks.Their different color structure from conventional hadrons can help us improve the understanding of strong interaction.Quantum Chromodynamics(QCD)is the fundamental theory for strong interaction.It can solve the basic hadron problem through perturbation theory in high-energy region.However,in low-energy region,perturbation theory is not applicable because of the large coupling constant.Non-perturbation approaches become very important in the study in this region.By solving the four-body and five-body Schrodinger equations accurately,we studied serval multiquarks which have not been observed in experiment.The numberical method is Gaussian expansion method.The constituent quark model we used reproduces the low-lying mesons and baryons spectra very well.But for multiquarks,its reliability remains unclear.In order to study this,we first focus on the simplest case,double-heavy tetraquarks.We found serval bound states in different systems,and the deep bound states agree with lattice QCD results very well.In the meantime,we study the contributions from different parts of Hamiltonian,and found that the color-electric force of Coulomb like between two heavy quarks cause this large binding.We calculate the two-body density distribution and discuss the spatial structures.We also study the ssscc pentaquark.There is no bound state in this system,so we focus on the resonant states.In this process,all scattering channels are taken into account.To distinguish resonant states and continuum states,we apply real-scaling method.Our calculation found serval sharp resonant states with compact structures which can be confirmed in experiment or lattice QCD.