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 Ξ^-Ξ^- system at a pion mass of m_π~390 MeV are presented. Calculations were performed with an anisotropic nf=2+1 clover discretization in four lattice volumes of spatial extent L~2.0, 2.5, 2.9, and 3.9 fm, with a lattice spacing of bₛ~0.123 fm in the spatial direction and bₜ~bₛ/3.5 in the time direction. Using the results obtained in the largest two volumes, the Ξ^-Ξ^- is found to be bound by B_Ξ^-Ξ^-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 Bd=11(05)(12) MeV and Bₙₙ=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 BH=13.2(1.8)(4.0) MeV at this pion mass, updating our previous result.