Disentangling different structures in heavy-light four-quark states

Models proposed to explain recently discovered heavy-light four-quark states already assume certain internal structures, i.e., the (anti)quark constituents are grouped into diquark/antidiquark clusters, heavymeson/light-meson clusters (hadrocharmonium) or heavy-light meson molecules. We propose and use an approach to four-quark states based on Dyson-Schwinger and Bethe-Salpeter equations that has the potential to discriminate between these models. We study the masses of heavy-light cq (q) over bar(c) over bar and cc (q) over bar(q) over bar four-quark states with q 1/4 u, d, s and quantum numbers I(J(PC)) = 0(1++); 1(1+-); (0++) and 1(0+); (1+); 1(1+). We identify the dominant components of the ground states with these quantum numbers and suggest candidates for corresponding experimental states. Most notably, we find strong heavy-light meson-meson and negligible diquark-antidiquark components in all cq (q) over bar(c) over bar states, whereas for cc (q) over bar(q) over bar states diquarks are present. A potential caveat in the I = 0 channels is the necessary but costly inclusion of c c components which is relegated to future work.