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 ccˉ and hybrid ccˉg state. From this conjecture we find a possible explanation of the famous ρ−π puzzle.
@article{arxiv.0805.1943,
title = {Hybrid Charmonium and the $\rho-\pi$ Puzzle},
author = {Leonard S. Kisslinger and Diana Parno and Seamus Riordan},
journal= {arXiv preprint arXiv:0805.1943},
year = {2009}
}