Researchers have extended a previous diabatic framework for the charmonium-like meson spectrum below 4.3 GeV by incorporating the complex scaling method. This new approach explicitly integrates couplings to the meson-meson continuum, allowing for a more comprehensive description of its contributions to physical states. A key advantage of this method is that it treats bound and resonant states on an equal footing, enabling the direct extraction of decay widths from complex energy eigenvalues without introducing any additional free parameters.

The study has allowed for the calculation of channel weights and complex root-mean-square radii (rRMS) of these mesons, shedding light on their internal structures. Specifically, it was found that the χc1(3872), ψ(4040), and ψ(4230) states exhibit significant molecular characteristics. Furthermore, the authors propose the X(3940) as a candidate for a state with quantum numbers JPC=1++ and discuss in detail the nature of the χc0(2P) resonance.

This advance in understanding the charmonium-like meson spectrum is crucial for particle physics. The ability to determine decay widths directly from energy eigenvalues without free parameters represents a substantial methodological improvement. The results contribute to unraveling the complex structure of these exotic states, which often challenge simple quark model descriptions, and open new avenues for future experimental and theoretical investigations in the search for new hadronic states.