Scalar glueball and meson spectroscopy in unquenched lattice QCD with improved staggered quarks

We present results of an exploratory study of singlet scalar states in unquenched QCD using both glueball and meson operators. Results for non-singlet non-strange scalar mesons are also presented. We use Asqtad improved staggered fermions and gauge configurations generated by the MILC collaboration at lattice spacings of .12 and .09 fm. In this formulation, the glueball mass is not significantly different from the quenched value at finite lattice spacing. Significant taste violations are present in the scalar sector. At light quark masses, decay channels complicate the mass determinations. There is some evidence that the non-strange singlet meson lies below the non-singlet meson.Comment: Lattice 2005 (hadron spectrum and quark masses), 6 pages, 4 figure

Towards measuring the eta' mass with N_f=2+1 staggered fermions

Because the propagators of flavor-singlet states incorporate disconnected diagrams, they are uniquely sensitive to any differences in the actions governing sea and valence fermions on the lattice. As such, they present an important test of the validity of the ``fourth-root trick'' in the staggered fermion formulation. The pseudoscalar's relationship to topological charge also makes it of theoretical interest. We present preliminary results from our measurements of flavor-singlet pseudoscalar mesons on 2+1 flavor Asqtad lattices, and discuss some strategies for improving the signal-to-error ratio of disconnected singlet correlators.Comment: 7 pages, 5 figures, to appear in proceedings of Computational Hadron Physics, Nicosia, Cyprus, 14-17 Sep 200