Phenomenological Study On The Intrinsic Sea Content In Nucleon And The Nucleon Spin

So far,the polarized and depolarized deep inelastic scattering of lepton-nucleon have not only provided scholars with a lot of information about the distribution of quarks and gluons within nucleon but also provided a good experimental basis for theoretical study and model establishment of some properties in nucleon.In 1988,the EMC published their experimental data,which showed that only a small part of the nucleon's spin was carried by the quarks.However,it is obvious that the nucleon's spin is completely carried by the spin of the quarks and the strange quarks do not contribute to the spin of the nucleon under the traditional constituent quark model.These results,obtained in the classical quark model,are not consistent with those obtained in the polarized deep inelastic scattering experiment,so the study of the nucleon's spin has become an important task in the current nucleon's structure research.At present,many experimental measurements have shown that the anti-light quarks in nucleon were asymmetric,and strange sea quarks also contributed to the spin of nucleon.Therefore,phenomenologically,considering the higher Fock components in the nucleon wave function is a good modification of the three-quark constituent model.The present thesis is organized as follow:in chapter 1,the discovery of the elementary particle,the basic properties of QCD,and the experimental investigation of the nucleon spin structure are reviewed briefly.In chapter 2,the extended chiral constituent quark model(E-?CQM)and the wave functions of nucleon in this chapter are introduced.The contribution of five-quark components is calculated in chapter 3 and the summary and outlook are proposed in chapter 4.The main research methods are as follow:firstly,the flavor,color,spin and orbital wave functions of three-quark and five-quark systems are constructed using the knowledge of group theory.The wave functions in the full space of the five-quark system are acquired through coupling four-quark subsystems and the rest of the anti-quark states,and at last,there are 34 the possible five-quark configurations for the octet baryons through symmetric coupling.In our model,the transition between the three-quark state and the five-quark states is realized by the ³P₀mechanism,the computation of transition operator matrix elements shows that only 17 configurations exist in the ground-state nucleon.Moreover,these configurations can be simply divided,according to the symmetry of orbit-spin space,into the following four categories:[31]_X[22]_S,[31]_X[31]_S,[4]_X[22]_Sand[4]_X[31]_S.In present work,the contribution to nucleon spin,from both quarks spin and orbital angular momentum of quarks,are calculated.Additionally,the relevant coupling constants in the semileptonic decay are studied in our model.According to the results,our values can be basically consistent with the prediction values of other phenomenological models and the data of each experimental group.This shows the effect of the intrinsic sea quarks in the nucleon on the spin properties of the nucleon,and shows that it is a feasible way to extend the model by adding all possible five-quark components on the basis of the traditional constituent quark model.This fact shows the rationality of the model is used in this work and lays a foundation for analyzing other properties of nucleon.In future work,we can optimize the numerical results by considering relativistic correction to the study of nuclear spin,and further investigate the spin content of other baryons in the octet states using this method.Finally,it can provide more theoretical support for the the hadron physics experiment.