Hybrid Charmonium and the $\rho -\pi$ Puzzle

Abstract

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 ${\Psi }^{\prime }(2S)$ state, about 600 Mev above the $J/\Psi (1S)$ state. Since our solution is not consistent with a pure hybrid at this energy, we conclude that the ${\Psi }^{\prime }(2S)$ state is probably an admixed $c\bar{c}$ and hybrid $c\bar{c}g$ state. From this conjecture we find a possible explanation of the famous $\rho -\pi$ puzzle.

Comments: 9 pages, 7 figures