Baryon Spectrum In The Chiral SU(3) Quark Model

The half-integer spin particles such as nucleon (proton, neutron), hyperon (Λ,Σ,Ξ,etc.),Δresonance are known as baryon . These particles at least including three quarks are the most basic internal structure particles in the nature.The spectrum is the extremely effective tool to explore material and micro-structure and has great significance in the history of the physical development. One of important objective of the baryon spectrum research is to use the baryon spectrum to acquaint the interaction between quarks and then study of the baryon structure.Since 1964 the U.S. physicist Gell-Mann proposed the new theory of matter composition - quark model, people began to study the quark-level Spectrum. It is now widely considered the basic theory of strong interactions is the quantum chromodynamics QCD which is based on the quark and gluon freedom and standardized field theory. The research of the baryon-structure has turned into the standard model. People began to use this theory to study the interaction between the baryons and the baryon spectrum. Baryon structure and baryon interaction become a basic physical problem once again.It is hoped that the baryon structure can be explanted by the QCD, but it is still difficult to interpret the baryon structure directly from the QCD, because of the non-perturbation feature of the low-energy QCD. The main means to acquaint the baryon structure also relies on QCD model in current. In the QCD model, the constituent quark mode(lCQM)is most successful. The model assumed that non-relativistic approximation is still valid. The confining quarks describe by the quarks jailed potential, the asymptotic freedom interaction describes by the adscititious perturbation-gluon exchange potential.Non-perturbation QCD plays a very important role in the light quark system. In the study of the N-N interaction, the effective way to describe the interaction is to bring in the quark - chiral field coupling. The chiral SU (3) quark model is based on SU (2)σmodel and promote to the SU (3) flavor space, and bring in all octuple and the single-scalar meson and pseudoscalar meson. In the chiral SU (3) quark model, the nonet pseudoscalar meson exchange and the nonet scalar meson exchange are used to describe the long-distance nuclear power, single-gluon exchange potential is used to describe the behave of the short-distance perturbation QCD.In recent years, Shen Pengnian, Riska and Glozman etc. apply the quark - chiral coupled model to study the baryon structure, and found the quarks - chiral coupled is very important in the description of the baryon structure.This thesis only discusses the spectrum of three quarks baryon composed by u, d, s. Construct the orbital space harmonic oscillator wave functions which meets the requirement of the S 3 group replacement in Jacobi coordinate. Then write out the baryon wave function met with the demand of symmetry, and calculate the baryon mass in the chiral SU (3) quark model.The results display that the chiral SU(3) quark model can comparatively well describe the ground properties of the baryon spectrum. However, in the excited states cases, the results show larger deviations that indicate the complexity of the baryon structure. In the quark model, it is only an approximation to consider only valence quarks and essential to consider sea quarks. For this reason ,the next work is to consider a mix state. At the same time, also shows that the transition between different states is more sensitive to the baryon structure and provide more stringent testing to the model of the baryon.