Meson-baryon scattering lengths from mixed-action lattice QCD

The pi(+)Sigma(+), pi(+)Xi(0), K(+)p, K(+)n, and (K) over bar (0)Xi(0) scattering lengths are calculated in mixed-action Lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations at four light-quark masses, and at two light-quark masses on the fine MILC configurations. Heavy-baryon chiral perturbation theory with two and three flavors of light quarks is used to perform the chiral extrapolations. To the order we work in the three-flavor chiral expansion, the kaon-baryon processes that we investigate show no signs of convergence. Using the two-flavor chiral expansion for extrapolation, the pion-hyperon scattering lengths are found to be a(pi+Sigma+) = -0.197 +/- 0.017 fm, and a(pi+Xi 0) = -0.098 +/- 0.017 fm, where the comprehensive error includes statistical and systematic uncertainties.