Simple Observables from Fat Link Fermion Actions

A comparison is made of the (quenched) light hadron spectrum and of simple matrix elements for a hypercubic fermion action (based on a fixed point action) and the clover action, both using fat links, at a lattice spacing a= 0.18 fm. Renormalization constants for the naive and improved vector current and the naive axial current are computed using Ward identities. The renormalization factors are very close to unity, and the spectroscopy of light hadrons and the pseudoscalar and vector decay constants agree well with simulations at smaller lattice spacings (and with experiment).Comment: 22 pages, 12 postscript figures, Revtex plus eps

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

Evidence for a bound H dibaryon from lattice QCD

We present evidence for the existence of a bound H dibaryon, an I = 0, J = 0, s = -2 state with valence quark structure uuddss, at a pion mass of m(pi) similar to 389 MeV. Using the results of lattice QCD calculations performed on four ensembles of anisotropic clover gauge-field configurations, with spatial extents of L similar to 2.0, 2.5, 3.0, and 3.9 fm at a spatial lattice spacing of b(s) similar to 0.123 fm, we find an H dibaryon bound by B(infinity)(H) = 16.6 +/- 2.1 +/- 4.6 MeV at a pion mass of m(pi) similar to 389 MeV