A Refined Analysis on the $X(3872)$ Resonance

TL;DR

This paper analyzes the nature of the X(3872) meson by fitting decay data with different models, concluding it is mainly a charmonium Breit-Wigner resonance with minor D D* molecular contributions.

Contribution

It introduces a combined analysis of X(3872) as a Breit-Wigner resonance and a D D* molecule, providing a refined understanding of its structure.

Findings

Data favors X(3872) as a mainly charmonium resonance

Optimal fit yields mass 3871.2 MeV and width 6.5 MeV

Supports a mixed resonance and molecular interpretation

Abstract

We study the property of the $X(3872)$ meson by analyzing the $B\to K D\bar D^*$ and $B\to K J/\psi \pi^+\pi^-$ decay processes. The competition between the rescattering mediated through a Breit-Wigner resonance and the rescattering generated from a local $D\bar{D}^* \to D\bar{D}^*$ interaction is carefully studied through an effective lagrangian approach. Three different fits are performed: pure Breit-Wigner case, pure $D\bar{D}^*$ molecule case with only local rescattering vertices (generated by the loop chain), and the mixed case. It is found that data supports the picture where X(3872) is mainly a ($\bar cc$) Breit-Wigner resonance with a small contribution to the self-energy generated by $\bar DD^*$ final state interaction. For our optimal fit, the pole mass and width are found to be: $M_X=3871.2\pm0.7$MeV and $\Gamma_X=6.5\pm1.2$MeV.