BB Potentials in Quenched Lattice QCD

The potentials between two B-mesons are computed in the heavy-quark limit using quenched lattice QCD at mπ ∼ 400 MeV. Nonzero central potentials are clearly evident in all four spin-isospin channels, (I,sl) = (0,0), (0,1), (1,0), (1,1), where sl is the total spin of the light degrees of freedom. At short distance, we find repulsion in the I ≠ sl channels and attraction in the I=sl channels. Linear combinations of these potentials that have well-defined spin and isospin in the t-channel are found, in three of the four cases, to have substantially smaller uncertainties than the potentials defined with the s-channel (I,sl), and allow quenching artifacts from single hairpin exchange to be isolated. The BB*π coupling extracted from the long-distance behavior of the finite-volume t-channel potential is found to be consistent with quenched calculations of the matrix element of the isovector axial-current. The tensor potentials in both of the sl = 1 channels are found to be consistent with zero within calculational uncertainties.