LAUSR

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, heavy-meson/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 cqq¯c¯ and ccq¯q¯ four-quark states with q=u, d, s and quantum numbers I(JPC)=0(1++),1(1+-),0(0++) and 1(0+),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 cqq¯c¯ states, whereas for ccq¯q¯ states diquarks are present. A potential caveat in the I=0 channels is the necessary but costly inclusion of cc¯ components which is relegated to future work.