The Study Of Multiquark States And Related Problems

People have always been very interested in studying the dibaryon states.Deuteron is the only dibaryon state discovered by experiment early,however,we call it molecular state since its binding energy is small.Until recently,the d*exotic dibaryon state was confirmed by COSY experiment.Now the research on the multiquark states has aroused general interest of hadron physics.In this work we investigate the problems related to multiquark states,mainly how to con-struct multiquark wave functions from the representation theory of permutation group,also the dibaryon states without and with strangeness in the chiral SU(3)quark model.Firstly,the representation of permutation group and projection operator are studied and applied to construct the wave functions of three-quark in flavor and spin spaces.We also study how to construct four-quark and five-quark wave functions and find that this method can be generalized to construct multiquark state.Then,by using resonance group method,we investigate the dibaryon states without s-trangeness in the chiral SU(3)quark model,mainly the structure of deuteron and two dibaryons of ?? with spin singlet and spin triplet.We compare the different structures and find that one-gluon exchange provides repulsive interaction to spin singlet state and contributes strong attraction to spin triplet state,hence the effect of hidden color channel on spin triplet state is larger and important.Finally,the dibaryon with strangeness-3 has also preliminarily been studied,the wave function from hidden color channel is constructed,and further the interaction matrix elements in color-flaovr-spin space are calculated.However,the dynamical calculation has not been carried out in the chiral SU(3)quark model.The multiquark issue is currently of interest experimentally and theoretically,and it is meaningful and worthwhile to continue this research in the future.