Structure of the X(3872) as explained by a diffusion Monte Carlo calculation

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 Schrodinger equation that describes this state as a c (c) over barn (n) over bar (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(D) over bar*(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).

Automated summary

Two decades after its discovery, the nature of the X(3872) exotic resonance remains under scrutiny, with recent research suggesting a meson-meson molecular configuration as preferred, contrary to the usual assumption of a D-0(D) over bar*(0) molecule.