Spin forces in charmonium spectroscopy

The observed ψ′(3.68)-ψ′′(3.77) structure in e+e- annihilation implies the existence of a tensor-force effect in charmonium spectroscopy. We show that the magnitude of the effect is consistent with an analysis of PJ3 levels using a phenomenological Hamiltonian linear in both L→•S→ and S12, the tensor force. Adding a linear σ→1•σ→2 term one can account for all known charmonium levels below 4 GeV and predict the location of the rest of the spectrum, in particular the P11 state at 3.27 GeV.