bbu¯d¯ and bsu¯d¯ tetraquarks from lattice QCD using two-meson and diquark-antidiquark variational basis

We present a lattice QCD investigation of isoscalar tetraquark systems involving bottom quarks with explicit flavor content bbu¯d¯ and bsu¯d¯. In the doubly bottom sector, the study focuses on axial-vector JP=1+ quantum numbers, whereas in the bsu¯d¯ channel, both axial-vector JP=1+ and scalar JP=0+ quantum numbers are investigated in search of signatures for possible tetraquark bound states. The calculations are performed on four ensembles with dynamical quark fields up to the charm quark generated by the MILC Collaboration, with lattice spacings ranging from approximately 0.058 to 0.12 fm, and at different values of the valence light quark mass mu/d, corresponding to pseudoscalar meson masses, Mps=0.5, 0.6, and 0.7 GeV. The energy eigenvalues in the finite volume are determined by applying a variational procedure to correlation matrices constructed from two-meson interpolating operators and diquark-antidiquark operators. Continuum extrapolated elastic S-wave scattering amplitudes of BB*, KB*, and KB are extracted from the ground-state eigenenergies following a finite-volume analysis Lüscher. The chiral and continuum extrapolated binding energy estimates for the isoscalar axial-vector doubly bottom tetraquark Tbb from the extracted elastic BB* S-wave scattering amplitudes is found to be ΔETbb(1+)=−116(−36+30) MeV. In the bsu¯d¯ system, no statistically significant deviations were observed in the ground-state energies from the respective elastic threshold energies, leading to no conclusive evidence for any bound states.