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 m_π~390 MeV, a spatial volume of L³~(2.5 fm)³, and a spatial lattice spacing of b~0.123 fm. L\"uscher'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.