Four-quark states with charm quarks in a two-body Bethe-Salpeter approach

We study the internal structure of a range of four-quark states with charm quark contributions using a two-body Bethe-Salpeter equation. Thereby, we examine charmonium-like states with hidden charm and quark content c (c) over barq (q) over bar, open-charm states with quark content cc (q) over bar(q) over bar and all-charm states with cc (c) over bar(c) over bar. In particular we study the internal competition between meson-meson components and diquark-antidiquark components in the wave functions of these states. Our results indicate that the chi(c1)(3872) and the Z(c)(3900) are predominantly D (D) over bar* states and that the recently discovered open-charm state T-cc(+) is dominated by an internal DD* component. In both cases the diquark components are negligible. For the all-charm state X (6900) with as yet unknown quantum numbers we identify candidates in the excitation spectra of 0(+) and 1(+) states. Furthermore, our framework serves to provide predictions for further, yet undiscovered open and hidden charm four-quark states.

Automated summary

This study investigates the internal structure of four-quark states with charm quark contributions using a two-body Bethe-Salpeter equation. The results reveal the dominant components in known quark states and propose candidates for yet unknown all-charm states.