Electroproduction Of Low Resonances Of Nucleon In The Colored Quark Cluster Model

The nucleon and its resonances have been intensively investigated within the framework of the constituent quark models. However, the predictions of the three quark constituent quark model for the spatial excited nucleon are not so successful, in particular for the longstanding mass-reverse problem of P11(1440) and S11(1535). Much experimental data on electroproduction of the nucleon resonances have been accumulated for decades, and correspondingly, the theoretical attempts to build a quantitative model for electroproduction of the nucleon resonances is necessary to understand their internal structures.The additional intrinsic non-perturbative five-quark components have been suggested to play an significant role for explaining well-established data. Based on such a colored quark cluster model, the electroproduction of low resonances of nucleon has been studied previously with the nonrelativistic electromagnetic transtion operator. In this thesis, the electroproduction amplitudes of low resonances of nucleon are calculated by including both the additional five-quark configurations of the lowest energy in the wave functions and in particular the relativistic correction to the electromagnetic transition operator. The calculated results show that the relativistic corrections have remarkable contribution to the electroproduction amplitudes and have the same order with those from the five-quark component. Both contributions together improve agreements with experimental data, which provides the significant information on the internal structure of nucleon and its resonances.The main content is as follows. First, a brief summary on five-quark configurations in baryons is presented, and the wave functions of the nucleon and its low resonances are presented with the additional five-quark configurations of the lowest energy. Secondly, the relativistic corrections to the transition operator are considered, which include spin-orbit term and Wigner rotation contributions. Finally, the electroproduction amplitudes of the low resonances of nucleon are calculated with the wave functions with the five-quark component and the relativized transition operator, and the numerical results are given and are compared with the experimental data.