Deuteron and exotic two-body bound states from lattice QCD

Results of a high-statistics, multivolume lattice QCD exploration of the deuteron, the dineutron, the H-dibaryon, and the Xi(-)Xi(-) system at a pion mass of m(pi) similar to 390 MeV are presented. Calculations were performed with an anisotropic n(f) = 2 + 1 clover discretization in four lattice volumes of spatial extent L similar to 2.0, 2.5, 2.9, and 3.9 fm, with a lattice spacing of b(s) similar to 0.123 fm in the spatial direction and b(t) similar to b(s)/3.5 in the time direction. Using the results obtained in the largest two volumes, the Xi(-)Xi(-) is found to be bound by B(Xi-Xi-)0 = 14.0(1.4)(6.7) MeV, consistent with expectations based upon phenomenological models and low-energy effective field theories constrained by nucleon-nucleon and hyperon-nucleon scattering data at the physical light-quark masses. Further, we find that the deuteron and the dineutron have binding energies of B-d = 11(05)(12) MeV and B-nn = 7.1(5.2)(7.3) MeV, respectively. With an increased number of measurements and a refined analysis, the binding energy of the H-dibaryon is B-H = 13.2(1.8)(4.0) MeV at this pion mass, updating our previous result.