Exotic few-body systems with a heavy meson

Abstract

Hadronic molecular states have been considered to be the structure the exotic heavy hadrons near the threshold. In the formation of the molecules, new symmetry appearing in the heavy quark sector, called the heavy quark symmetry, is important. One of the essential roles of this symmetry is to enhance the one pion exchange potential which arises through the mixing of heavy pseudoscalar and heavy vector mesons. In this study, we consider the hadronic molecules formed by the heavy meson P(*)=D¯(*), B(*) and a nucleon N, being P(*)N and P(*)NN few-body states. As the interaction between P and N, the π exchange and vector meson (ρ and ω) exchanges are employed. By solving the coupled-channel schrödinger equations for PN(N) and P(*)N(N), we obtain the bound and resonant states in the charm and bottom sector, and in the infinite heavy quark mass limit. In the bound and resonant states, the tensor force of the one pion exchange potential in the PN − P*N mixing plays an crucial role to generate the strong attraction. The obtained states are located near the PN(N) and P(*)N(N) thresholds. In the heavy quark mass limit, the degenerate states with different angular momenta are found.