Seminario di Fenomenologia delle Particelle Elementari

The study of exotic hadrons is one of the interesting topics in hadron and nuclear physics.
Especially near the hadron-hadron thresholds in the heavy flavor sector, many exotic quarkonia called XYZ have been reported by the experiments.
The properties of those exotic states are not explained by the conventional quark model picture, three quark as baryons and quark-antiquark as mesons, but considered to be a multiquark
state.
The charged charmonium Zc(3900) reported by BESIII is a candidate of the genuine exotic state, because the ordinal charmonium should have no electric charge.
Since the mass is obtained close to DDbar* threshold, Zc(3900) is discussed as the DDbar* molecular state.
On the other hand, the recent Lattice QCD simulation by HALQCD studies that Zc(3900) is the threshold cusp, which is induced by the strong pi J/psi-DDbar* potential.
To understand the hadron dynamics, such as hadron (quasi-)bound state and cusp structure, near the thresholds, the hadron-hadron interaction is an important ingredient, while the hadron
interaction is not established yet.
In this talk, we focus on the pi J/psi-DDbar* potential, which is discussed by the D meson exchange and quark exchange models.
In the meson exchange model, the hadron is the effective degrees of freedom, while the constituent quarks inside the hadron describe the interaction in the quark exchange model.
We find the difference between results of two models.
The potentials obtained in this study will be useful to understand the hadron scattering near the threshold.