Light Hadron Spectrum Based On The Relativistic Quark Model

This thesis examines two problems of strong quark interaction using the relativistic quark model, which falls in two general areas. Before going to these problems, we add a brief introduction to the background.In the first chapter, we present a brief review of the physical background of our research. After introducing the standard model and the classification of the subatomic particles, we describe the present status of hadrons and quantum chromodynamics (QCD), the theory of strong interaction. The models and phenomenology of hadrons are also outlined at the end of this chapter.In the second chapter, we focus on the estimate of the't Hooft coupling constant g_t within the framework of relativistic model. Starting with a brief review of the N_c QCD, we present in detail the method and results of estimating the't Hooft coupling constant g_t based on the 4-dimensional formulation of the 2D relativistic Hartree model of a baryon inspired by large N_c QCD. We also study the mass splitting of the ground-state baryons in terms of the same model, by which the Hartree wavefunctions of light quarks are obtained. By fitting the spectra of decuplet and octet bayons, we obtain the't Hooft coupling constant g_t to be around 1.57. We generalize the scenario to the case of heavy baryon, such as Ac, g_t values which does not deviate much from 1.57, as well as to the case of mesons with g_t far from that for baryons. The implication of results is discussed.In the third chapter, we employ the auxiliary field method to study the spectrum of light mesons and obtain the solution to the relativized quark model, that is the Godfrey-Isgur model. A new mass formula is obtained for the light and heavy mesons, which agrees with the Regge trajectories of the meson sonsidered. We perform a preliminary study on the spectroscopy of light mesons (?,p,K,K*,?,?), with a comparison with the previous model calculation and experimental data available.In the fourth chapter, a summary is given at the end of this paper, and we provide an outline of the future in this field.