Spin degeneracy in multi-hadron systems with a heavy quark

We study multi-hadron systems with a single heavy quark (charm or bottom) in the limit of heavy quark mass. The spin degeneracy of the states with quantum numbers (j+1/2)P and (j−1/2)P for j≠0, known in a normal hadron, can be generalized to multi-hadron systems. The spin degeneracy is the universal phenomena for any multi-hadron systems with a single heavy quark, irrespective of their internal structures, including compact multi-quarks, hadronic molecules and exotic nuclei. We demonstrate the spin degeneracy in the hadronic systems formed by a heavy hadron effective theory: P(⁎)N states with a P(⁎)=D¯(⁎), B(⁎) meson and a nucleon N, and a P(⁎) meson in nuclear matter. The spin degeneracy in the multi-hadron systems with a single heavy quark provides us with useful information about mass spectra, decays and productions in a model-independent manner.