QCD Sum Rules for the X(3872) as a mixed molecule-charmoniun state

TL;DR

This paper uses QCD sum rules to analyze the X(3872) meson, suggesting it is predominantly a charmonium state with a small molecular admixture, consistent with experimental mass and decay width.

Contribution

It provides a quantitative estimate of the mixing angle and the molecular component proportions of X(3872) using QCD sum rules, offering new insights into its internal structure.

Findings

X(3872) is about 97% charmonium with a small molecular component.

The mixing angle etween 5 and 13 degrees fits experimental data.

Mass and decay width predictions agree with experimental measurements.

Abstract

We use QCD sum rules to test the nature of the meson X(3872), assumed to be a mixture between charmonium and exotic molecular [c\bar{q}][q\bar{c}] states with J^{PC}=1^{++}. We find that there is only a small range for the values of the mixing angle, \theta, that can provide simultaneously good agreement with the experimental value of the mass and the decay width, and this range is \theta between 5 and 13 degrees. In this range we get m_X=(3.77 \pm 0.18) GeV and \Gamma(X to J/\psi \pi^+ \pi^-)=(9.3 \pm 6.9) MeV, which are compatible, within the errors, with the experimental values. We, therefore, conclude that the X(3872) is approximately 97% a charmonium state with 3% admixture of \sim 88% D^0D^{*0} molecule and \sim 12% D^+D^{*-} molecule.