Search for (b)over-bar(b)over-barus and (b)over-bar(c)over-barud tetraquark bound states using lattice QCD

We use lattice QCD to investigate the existence of strong-interaction-stable antiheavy-antiheavy-light-light tetraquarks. We study the (b) over bar(b) over bar us system with quantum numbers J(P) = 1(+) as well as the (b) over bar(c) over bar ud systems with quantum numbers I(J(P)) = 0(0(+)) and I(J(P)) = 0(1(+)). We carry out computations on five gauge-link ensembles with 2 thorn 1 flavors of domain-wall fermions, including one at the physical pion mass. The bottom quarks are implemented using lattice nonrelativistic QCD, and the charm quarks using an anisotropic clover action. In addition to local diquark-antidiquark and local meson-meson interpolating operators, we include nonlocal meson-meson operators at the sink, which facilitates the reliable determination of the low-lying energy levels. We find clear evidence for the existence of a strong-interaction-stable (b) over bar(b) over bar us tetraquark with binding energy (-86 +/- 22 +/- 10) MeV and mass (10609 +/- 22 +/- 10) MeV. For the (b) over bar(c) over bar ud systems we do not find any indication for the existence of bound states, but cannot rule out their existence either.

Automated summary

In this study, lattice QCD is used to investigate the existence of stable antiheavy-antiheavy-light-light tetraquarks. Clear evidence for the existence of a strong-interaction-stable (b) over bar(b) over bar us tetraquark was found.