Is X(3872) a molecule?

TL;DR

This paper examines the potential molecular nature of X(3872) and other exotic states, highlighting inconsistencies in pion exchange models and the sensitivity of binding results to uncertain parameters.

Contribution

It clarifies the formalism of pion exchange models, exposes inconsistencies in existing literature, and explores conditions for binding in charm and bottom sectors.

Findings

X(3872) can be a bound state but is highly sensitive to parameters.

Bound states in the B Bbar sector are possible.

Exotic combinations with cc or bb quantum numbers may bind under certain conditions.

Abstract

We show that the literature on pion exchange between charm and bottom mesons is inconsistent. We derive the formalism explicitly, expose differences between papers in the literature and clarify the implications. We show that the X(3872) can be a bound state but that results are very sensitive to a poorly constrained parameter. We confirm that bound states in the B Bbar sector are possible. The circumstances whereby exotic combinations can bind with cc or bb quantum numbers are explored.