Spin degeneracy of Hadronic molecules in the heavy quark region

Hadronic molecules have been considered to appear close to the hadron-hadron threshold. For the heavy mesons, $\overline{D}$ and B, the one pion exchange potential is enhanced by the mass degeneracy of heavy pseudoscalar and vector mesons, caused by the heavy quark spin symmetry. In this study, we investigate new hadronic molecules formed by the heavy meson $P^{(\ast )}={\overline{D}}^{(\ast )},B^{(\ast )}$ and a nucleon N, being P ^(*) N. As the interaction between P ^(*) and N, the pion and vector meson (ρ and ω) exchanges are considered. By solving the coupled-channel Schrödinger equations for P N and P*N, we obtain the bound and resonant states in the charm and bottom sectors, and in the in nite heavy quark mass limit. In the molecular states, the PN − P*N mixing effect is important, where the tensor force of the one pion exchange potential generates the strong attraction. In the heavy quark limit, we obtain the degeneracy of the states for J ^P = 1/2⁻ and 3/2⁻. (paper)