High statistics analysis using anisotropic clover lattices: III. Baryon-baryon interactions

Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic-clover gauge-field configurations at a pion mass of mπ∼390 MeV, a spatial volume of L3∼(2.5 fm)3, and a spatial lattice spacing of b∼0.123 fm. Luescher's method is used to extract nucleon-nucleon, hyperon-nucleon, and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The isospin-3/2 NΣ interactions are found to be highly spin dependent, and the interaction in the 3S1 channel is found to be strong. In contrast, the NΛ interactions are found to be spin independent, within the uncertainties of the calculation, consistent with the absence of one-pion exchange. The only channel for which a negative energy shift is found is ΛΛ, indicating that the ΛΛ interaction is attractive, as anticipated from model-dependent discussions regarding the H dibaryon. The nucleon-nucleon (NN) scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN sector at this pion mass. This is consistent with our previous lattice QCD calculation of NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting is explored. In particular, focus is placed on the window of time slices for which the signal-to-noise ratio does not degrade exponentially, as this provides the opportunity to extract quantitative information about multibaryon systems.