X(3872) and Other Possible Heavy Molecular States

TL;DR

This paper systematically investigates heavy meson pairs for potential molecular states using meson exchange models, finding possible bound states like X(3872) and predicting others, with implications for experimental searches.

Contribution

It provides a comprehensive analysis of heavy meson pairs as molecular states, including new predictions for states like Z+(4051) and B*B, and discusses the nature of X(3872).

Findings

X(3764) is not a molecular state.

Strong attraction in D*D* with J=0,1 suggests possible molecules.

X(3872) can be interpreted as a molecular state.

Abstract

We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as $D\bar D$, $D^\ast\bar D$, $D^\ast \bar D^\ast$ in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through our investigation, we find that (1) the structure X(3764) is not a molecular state; (2) There exists strong attraction in the range $r < 1$ fm for the $D^*\bar D^*$ system with $J=0, 1$. If future experiments confirm $Z^+(4051)$ as a loosely bound molecular state, its quantum number is probably $J^{P}=0^+$. Its partner state $\Phi^{**0}$ may be searched for in the $\pi^0\chi_{c1}$ channel; (3) The vector meson exchange provides strong attraction in the $D^\ast \bar D$ channel together with the pion exchange. A bound state solution exists with a reasonable cutoff parameter $\Lambda\sim 1.4$ GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation; (4) The $B^\ast \bar B$ molecular state exists.