144 research outputs found
An Improved Action for Heavy Quarks
We extend the Fermilab method for heavy quarks to include all interactions of
dimension six in the action. We discuss a subtlety in the power counting, which
implies that, for heavy quarks, certain interactions of dimension seven are
commensurate with some of those of dimension six. We then present tree-level
matching conditions obtained from calculating the Compton scattering amplitude
for (lattice) QCD. When the matching conditions have been applied, the improved
action removes (tree-level) discretization errors of order
and .Comment: 1+5 pp., contribution to Lattice 2006(Quark Masses, Gauge Couplings,
and Renormalization
Spectral functions of charmonium from 2 flavour anisotropic lattice data
The spectral functions of QCD can give us insight into properties of hadrons,
and they are useful in probing the QCD vacuum. I will discuss the correlators
and spectral functions of charmonium in high temperature two flavour QCD. The
spectral functions have been obtained using the Maximum Entropy Method from
anisotropic lattice data using the conserved vector current. This work has been
done as part of the FASTSUM collaboration. We find that the spectral functions
for zero momentum are stable. At non-zero momentum the spectral functions are
less stable but still produce resonance and transport peaks. This work is part
of our programme to calculate the heavy quark diffusion constant.Comment: 7 pages, 5 figures, 31st International Symposium on Lattice Field
Theory LATTICE 201
Heavy-quark meson spectrum tests of the Oktay-Kronfeld action
The Oktay-Kronfeld (OK) action extends the Fermilab improvement program for
massive Wilson fermions to higher order in suitable power-counting schemes. It
includes dimension-six and -seven operators necessary for matching to QCD
through order in HQET power counting, for
applications to heavy-light systems, and in NRQCD power
counting, for applications to quarkonia. In the Symanzik power counting of
lattice gauge theory near the continuum limit, the OK action includes all
and some terms. To assess whether the
theoretical improvement is realized in practice, we study combinations of
heavy-strange and quarkonia masses and mass splittings, designed to isolate
heavy-quark discretization effects. We find that, with one exception, the
results obtained with the tree-level-matched OK action are significantly closer
to the continuum limit than the results obtained with the Fermilab action. The
exception is the hyperfine splitting of the bottom-strange system, for which
our statistical errors are too large to draw a firm conclusion. These studies
are carried out with data generated with the tadpole-improved Fermilab and OK
actions on 500 gauge configurations from one of MILC's ~fm,
-flavor, asqtad-staggered ensembles.Comment: 12 pages, 5 figure
Properties of charmonium in lattice QCD with 2+1 flavors of improved staggered sea quarks
We use the dynamical gluon configurations provided by the MILC collaboration
in a study of the charmonium spectrum and psi leptonic width. We examine sea
quark effects on mass splitting and on the leptonic decay matrix element for
light masses as low as m_s/5, while keeping the strange quark mass fixed and
the lattice spacing nearly constant.Comment: Lattice2003(heavy
Charmonium Spectrum on dynamical anisotropic lattices
We present a first study of the charmonium spectrum on N_f=2 dynamical,
anisotropic lattices. We take advantage of all-to-all quark propagators to
build spatially extended interpolating operators to increase the overlap with
states not easily accessible with point propagators such as radially excited
states of eta_c, psi, and chi_c, D-waves and hybrid states.Comment: 9 pages, 7 figures, Lattice 2005 Conferenc
D_s spectrum and leptonic decays with Fermilab heavy quarks and improved staggered light quarks
We present preliminary results for the D_s meson spectrum and decay constants
in unquenched lattice QCD. Simulations are carried out with 2+1 dynamical
quarks using gauge configurations generated by the MILC collaboration. We use
the ``asqtad'' a^2 improved staggered action for the light quarks, and the
clover heavy quark action with the Fermilab interpretation. We compare our
spectrum results with the newly discovered 0+ and 1+ states in the D_s system.Comment: 3pp. Presented at 21st International Symposium on Lattice Field
Theory (LATTICE 2003), Tsukuba, Ibaraki, Japan, 15-19 Jul 200
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