Study Of The Hidden-charm Exotic States:X(6900)and Zc(3900)

The traditional quark model successfully describes a meson composed of one quark and one antiquark,and a baryon composed of three quarks or three antiquarks.Quantum chromodynamics does not rule out other forms of exotic hadrons,such as hadronic molecular states,quark-gluon hybrid states,and multi-quark states.Since the quark model was proposed,people have been searching for exotic hadronic states.The main work of this thesis focuses on the exotic state hadrons X（6900）and Zc（3900）,including two parts,which are briefly explained below.In the first part,we study the properties of the fully heavy-flavor tetraquark candidate X（6900）in the framework of the coupled-channel scattering satisfying unitary property.By taking into account constraints from the heavy-quark spin symmetry,the couple-channel amplitude including theJ/ΨJ/Ψ?,x_c0x_c0 and x_c1x_c1is constructed to fit the experimentaldi-J/?event distributions.Our calculations show that X（6900）is mainly caused by a CDD pole.It is more like an elementary particle,and the two-meson components does not play a dominant role.The resonance poles determined from the coupled-channel study agree well with the experimental analysis.We find that the coupled-channel amplitude also has another pole,which lies below the?x_c0x_c0threshold and is a virtual state.We also predict the event distributions of?x_c0x_c0and?x_c1x_c1,which provide useful guide for future experimental measurement.In the other part of this thesis,we first introduce the theoretical formalism of the unitarization of the two-body scattering both in the infinite and finite volumes.Then we apply this formalism to the study of the Zc（3900）resonance in the J/ΨΠ?and D（?）coupled-channel scattering.The recent lattice finite-volume spectra are confronted with our predictions.