Hybrid Charmonium and the ρ−π Puzzle

Abstract EN

Using the method of QCD sum rules, we estimate the energy of the lowest hybrid charmonium state, and find it to be at the energy of the Ψ′(2S) state, about 600 MeV above the J/Ψ(1S) state.

Since our solution is not consistent with a pure hybrid at this energy, we conclude that the Ψ′(2S) state is probably an admixed cc¯ and hybrid cc¯g state.

From this conjecture, we find a possible explanation of the famous ρ−π puzzle.