Research Of Baryon Resonance Through Decay Of J/ψ

First,we introduce the background of the excited baryon problem.It is generated from the discovery of many hadron states,and inconsistance between the prediction of theoretical model and experimental results.So,physical information of hadron must be determined accurately. Baryon resonance,especially nucleon resonance is an important branch of the research field.Then,we describe the facilities of some important experimental collaborations:Jlab and BES,and state their way of dealing with experimental datas.Second,we discuss the dominated way of dealing with the intermediate or low energy scale of strong interaction: partial wave analysis and effective Lagrangian.Partial wave analysis has two forms:angular momentum tensor and helicity method.The former one is close to field theory,but contain high spin particles;the latter proceeds from principle of quantum mechanics,it is independant of the specific structure of the interaction model.Effective Lagrangian method is a generalization of field theory method,with the character of phenomenological theory.We display the procedure of applying these methods.At last we choose the second step of the decay of J/ψ particle i.e. the decay of nucleon resonance as our object, use the effective Lagrangian method to calculate the γ decay widths of three nucleon resonances: N*(1440) whose spin and parity is 1/2 and +1, N*(1520) whose spin and parity is 3/2 and -1, N*(1535) whose spin and parity is 1/2 and -1.Then,calculate π decay of N*(1440) whose spin and parity is 1/2 and +1. In the vector dominance model(VDM) we obtain the interaction Lagrangian between nucleon resonance and ω particle from the Lagrangian between nucleon resonance and photon,then calculate the ω decay widths of two nucleon resonances: N*(1875) whose spin and parity is 3/2 and-1;and N*(1900) whose spin and parity is 3/2 and +1.After comparing the decay width with the Particle Data Group(PDG),we determine the corresponding coupling constants.