Two decades after its unexpected discovery, the properties of the $X(3872)$ exotic resonance are still under intense scrutiny. In particular, there are doubts about its nature as an ensemble of mesons or having any other internal structure. We use a diffusion Monte Carlo method to solve the many-body Schrödinger equation that describes this state as a $c\overline{c}n\overline{n}$ ($n=u$ or $d$ quark) system. This approach accounts for multiparticle correlations in physical observables avoiding the usual quark-clustering assumed in other theoretical techniques. The most general and accepted pairwise Coulomb + linear-confining + hyperfine spin-spin interaction, with parameters obtained by a simultaneous fit of around 100 masses of mesons and baryons, is used. The $X(3872)$ contains light quarks whose constituent masses are given by the dynamical breaking of chiral symmetry. The same mechanism gives rise to Goldstone-boson exchange interactions between light quarks whose contribution, derived from a well extended chiral quark model, has been included in this analysis but plays a marginal role. It appears that a meson-meson molecular configuration is preferred but, contrary to the usual assumption of $D^0{\overline{D}}^{*0}$ molecule for the $X(3872)$, our formalism produces $\omega J/\psi$ and $\rho J/\psi$ clusters as the most stable ones, which could explain in a natural way all the observed features of the $X(3872)$.

• Received 26 May 2021
• Accepted 9 September 2021

DOI:https://doi.org/10.1103/PhysRevD.104.054036

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society