Importance of meson-meson and of diquark-antidiquark creation operators for a (b)over-bar(b)over-barud tetraquark

In recent years, the existence of a hadronically stable (b) over bar(b) over bar ud tetraquark with quantum numbers I(J(P)) = (1(+)) was confirmed by first principles lattice QCD computations. In this work we use lattice QCD to compare two frequently discussed competing structures for this tetraquark by considering meson-meson as well as diquark-antidiquark creation operators. We use the static-light approximation, where the two (b) over bar quarks are assumed to be infinitely heavy with frozen positions, while the light u and d quarks are fully relativistic. By minimizing effective energies and by solving generalized eigenvalue problems we determine the importance of the meson-meson and the diquark-antidiquark creation operators with respect to the ground state. It turns out, that the diquark-antidiquark structure dominates for (b) over bar(b) over bar separations r less than or similar to 0.25 fm, whereas it becomes increasingly more irrelevant for larger separations, where the I(J(P)) = 0(1(+)) tetraquark is mostly a meson-meson state. We also estimate the meson-meson to diquark-antidiquark ratio of this tetraquark and find around 60%/40%.

Automated summary

This study used lattice QCD to investigate a tetraquark particle and found that at short distances, the diquark-antidiquark structure dominates, while at larger distances, it is mostly a meson-meson state. The estimated meson-meson to diquark-antidiquark ratio of this tetraquark is around 60%/40%.