On the possibility of Deeply Bound Hadronic Molecules from single Pion Exchange

Abstract

Pion exchange in S-wave between hadrons that are themselves in a relative S-wave can shift energies by hundreds of MeV. In the case of charmed mesons $D,D^{\ast },D_0,D_1$ a spectroscopy of quasi-molecular states may arise consistent with enigmatic charmonium states observed above 4 GeV in $e^{+}{e}^{-}$ annihilation. A possible explanation of $Y(4260)\to \psi \pi \pi$ and $Y(4360)\to {\psi }^{\prime }\pi \pi$ is found. Searches in $D\bar{D}3\pi$ channels as well as B decays are recommended to test this hypothesis.

Comments: 5 pages, 1 figure. Version accepted to PRL. Equation 3 of v1 of this paper was wrong and has been taken into account in this version. Other minor typos corrected... conclusions unchanged