Excited-state spectroscopy of triply bottom baryons from lattice QCD

The spectrum of baryons containing three b quarks is calculated in nonperturbative QCD, using the lattice regularization. The energies of ten excited bbb states with JP=12 ⁺, 32 ⁺, 52 ⁺, 72 ⁺, 12 ^-, and 32 ^- are determined with high precision. A domain-wall action is used for the up, down, and strange quarks, and the bottom quarks are implemented with nonrelativistic QCD. The computations are done at lattice spacings of a≈0.11fm and a≈0.08fm, and the results demonstrate the improvement of rotational symmetry as a is reduced. A large lattice volume of (2.7fm)3 is used, and extrapolations of the bbb spectrum to realistic values of the light sea-quark masses are performed. All spin-dependent energy splittings are resolved with total uncertainties of order 1 MeV, and the dependence of these splittings on the couplings in the nonrelativistic QCD action is analyzed.