Novel Charmonium and Bottomonium Spectroscopies due to Deeply Bound Hadronic Molecules from Single Pion Exchange

TL;DR

This paper proposes that pion exchange can create deeply bound hadronic molecules, explaining certain charmonium states and predicting new exotic states, with implications for understanding heavy quarkonium spectroscopy.

Contribution

It introduces a novel mechanism of deeply bound hadronic molecules via S-wave pion exchange, providing a new explanation for enigmatic charmonium states and predicting exotic states.

Findings

Deeply bound states arise from S-wave pion exchange.

Explains Y(4260) and Y(4360) as molecular states.

Predicts an exotic 1^{-+} state near Y(4260).

Abstract

Pion exchange in S-wave between hadrons that are themselves in a relative S-wave is shown to shift energies by hundreds of MeV, leading to deeply bound quasi-molecular states. In the case of charmed mesons $D^*,D_1$ a spectroscopy arises consistent with enigmatic charmonium states observed above 4 GeV in $e^+e^-$ annihilation. A possible explanation of $Y(4260)\to \psi\pi\pi$ and $Y(4360) \to \psi'\pi\pi$ is found. We give results for all isospin and charge-conjugation combinations, and comment on flavor exotic doubly charmed states and bottomonium analogs. A search in $D\bar{D}3\pi$ is recommended to test this hypothesis. An exotic $1^{-+}$ is predicted to occur in the vicinity of the $Y$(4260).