90 research outputs found
Static-light mesons on a dynamical anisotropic lattice
We present results for the spectrum of static-light mesons from Nf=2 lattice
QCD. These results were obtained using all-to-all light quark propagators on an
anisotropic lattice, yielding an improved signal resolution when compared to
more conventional lattice techniques. In particular, we consider the inversion
of orbitally-excited multiplets with respect to the `standard ordering', which
has been predicted by some quark models.Comment: 3 pages with 3 figures. Talk by JF at "Quarks and Nuclear Physics",
Madrid 5th-10th June 200
Preconditioning Maximal Center Gauge with Stout Link Smearing in SU(3)
Center vortices are studied in SU(3) gauge theory using Maximal Center Gauge
(MCG) fixing. Stout link smearing and over-improved stout link smearing are
used to construct a preconditioning gauge field transformation, applied to the
original gauge field before fixing to MCG. We find that preconditioning
successfully achieves higher gauge fixing maxima. We observe a reduction in the
number of identified vortices when preconditioning is used, and also a
reduction in the vortex-only string tension.Comment: 9 pages, 4 figure
A non-perturbative study of the action parameters for anisotropic-lattice quarks
A quark action designed for highly anisotropic lattice simulations is
discussed. The mass-dependence of the parameters in the action is studied and
the results are presented. Applications of this action in studies of heavy
quark quantities are described and results are presented from simulations at an
anisotropy of six, for a range of quark masses from strange to bottom.Comment: 9 pages, 8 figure
Static-light hadrons on a dynamical anisotropic lattice
We present preliminary results for the static-light meson and baryon spectra
for QCD. The study is performed on an anisotropic lattice and uses a
new all-to-all propagator method allowing us to determine particle masses to a
high precision.Comment: 6 pages, Contribution to Lattice2005, PoS styl
Improving Algorithms to Compute All Elements of the Lattice Quark Propagator
We present a new exact algorithm for estimating all elements of the quark
propagator. The advantage of the method is that the exact all-to-all propagator
is reproduced in a large but finite number of inversions. The efficacy of the
algorithm is tested in Monte Carlo simulations of Wilson quarks in quenched
QCD. Applications that are difficult to probe with point propagators are
discussed.Comment: Talks presented by AOC and KJJ at Lattice2004(machines), Fermilab,
June 21-26, 2004. 6 pages, 6 figure
Role of center vortices in chiral symmetry breaking in SU(3) gauge theory
We study the behavior of the AsqTad quark propagator in Landau gauge on SU(3)
Yang-Mills gauge configurations under the removal of center vortices. In SU(2)
gauge theory, center vortices have been observed to generate chiral symmetry
breaking and dominate the infrared behavior of the quark propagator. In
contrast, we report a weak dependence on the vortex content of the gauge
configurations, including the survival of dynamical mass generation on
configurations with vanishing string tension.Comment: 8 pages, 9 figure
Charmonium spectral functions in Nf=2 QCD
We report on a study of charmonium at high temperature in 2-flavour QCD. This
is the first such study with dynamical fermions. Using an improved anisotropic
lattice action, spectral functions are extracted from correlators in the vector
and pseudoscalar channels. No signs of medium-induced suppression of the ground
states are seen for temperatures up to 1.5T_c, while at T~2T_c there are clear
signs of modifications. The current systematic and statistical uncertainties in
our data, in particular the relatively coarse lattice and small volume, do not
allow us to draw a firm conclusion at this stage.Comment: 6 pages, talk by JIS at Lattice 2005 (Non-zero temperature and
density
Practical all-to-all propagators for lattice QCD
A new method for computing all elements of the lattice quark propagator is
proposed. The method combines the spectral decomposition of the propagator,
computing the lowest eigenmodes exactly, with noisy estimators which are
'diluted', i.e. taken to have support only on a subset of time, space, spin or
colour. We find that the errors are dramatically reduced compared to
traditional noisy estimator techniques.Comment: 24 pages, 18 figure
Dynamical QCD simulations on anisotropic lattices
The simulation of QCD on dynamical (Nf - 2) anisotropic lattices is described. A method for nonperturbative renormalisation of the parameters in the anisotropic gauge and quark actions is presented. The precision with which this tuning can be carried out is determined in dynamical simulations on 8Âł X 48
and 8Âł X 80 lattices
Center vortices and the quark propagator in SU(2) gauge theory
We study the behavior of the AsqTad quark propagator in Landau gauge on quenched SU(2) gauge configurations under the removal of center vortices. In contrast to recent results in SU(3), we clearly see the infrared enhancement of the mass function disappear if center vortices are removed, a sign of the intimate relation between center vortices and chiral symmetry breaking in SU(2) gauge-field theory. These results provide a benchmark with which to interpret the SU(3) results. In addition, we consider vortex-only configurations. On those, the quark dressing function behaves roughly as on the full configurations, and the mass function picks up an almost linear momentum dependence.Patrick O. Bowman, Kurt Langfeld, Derek B. Leinweber, Alan O' Cais, Andre Sternbeck, Lorenz von Smekal and Anthony G. William
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