# X(3872) in an unquenched quark model

## TL;DR

This study models the X(3872) meson as a mixed state of charmonium and meson-meson components using an unquenched quark model with a modified pair creation operator, providing insights into its structure.

## Contribution

It introduces a modified quark pair creation operator considering energy and separation effects, and applies it to describe X(3872) as a mixed state.

## Key findings

- X(3872) is approximately 70% charmonium and 30% meson-meson components.
- The modified pair creation operator improves the modeling of meson structures.
- The wavefunctions are obtained via solving Schrödinger equations with Gaussian expansion.

## Abstract

In this paper, we calculate mass and probability fractions of meson-meson components of $X(3872)$ in an unquenched quark model. Different from most of other unquenched quark models, the quark pairs creation operator from $^3P_0$ is modified by considering effects of the created quark pair energy and separation between the created quark pair and the valence quark-pair. In the calculation, all the wavefunctions of mesons and the relative motion between two mesons are obtained by solving the corresponding Schr\"{o}dinger equation with the help of gaussian expansion method. The multi-channel coupling of quark-antiquark state with possible meson-meson states are performed. The results show that the $X(3872)$ can be described as a mixing state of dominant charmonium state (70\%) and meson-meson components (30\%).