10 research outputs found
Light Spectrum and Decay Constants in Full QCD with Wilson Fermions
We present results from an analysis of the light spectrum and the decay
constants f_{\pi} and f_V^{-1} in Full QCD with n_f=2 Wilson fermions at a
coupling of beta=5.6 on a 16^3x32 lattice.Comment: 3 pages, LaTeX with 4 eps figures, Talk presented at
LATTICE96(spectrum
An Estimate of alpha_S from Bottomonium in Unquenched QCD
We estimate the strong coupling constant from the perturbative expansion of
the plaquette. The scale is set by the 2S-1S and 1P-1S splittings in
bottomonium which are computed in NRQCD on dynamical gauge configurations with
nf=2 degenerate Wilson quarks at intermediate masses. We have increased the
statistics of our spectrum calculation in order to reliably extrapolate in the
sea-quark mass. We find a value of alpha_MS(m_Z) = 0.1118(26) which is somewhat
lower than previous estimates within NRQCD.Comment: LATTICE98(heavyqk
Preliminary Calculation of from Green Functions with Dynamical Quarks
We present preliminary results on the computation of the QCD running coupling
constant in the scheme and Landau gauge with two flavours of
dynamical Wilson quarks. Gluon momenta range up to about 7 GeV ( 5.6,
5.8 and 6.0) with a constant dynamical-quark mass. This range already allows to
exhibit some evidence for a sizable correction to the asymptotic
behaviour, as in the quenched approximation, although a fit without power
corrections is still possible with a reasonable . Following the
conclusions of our quenched study, we take into account correction to
the asymptotic behaviour. We find , which leads to
. The latter result has to be taken as a
preliminary indication rather than a real prediction in view of the systematic
errors still to be controlled. Still, being two sigmas below the experimental
result makes it very encouraging.Comment: 14 pages, 3 figs., 2 tabs., revte
Unquenching the Quark Model and Screened Potentials
The low-lying spectrum of the quark model is shown to be robust under the
effects of `unquenching'. In contrast, the use of screened potentials is shown
to be of limited use in models of hadrons. Applications to unquenching the
lattice Wilson loop potential and to glueball mixing in the adiabatic hybrid
spectrum are also presented.Comment: 6 pages, 3 ps figures, revtex. Version to appear in J. Phys.
QCD with dynamical Wilson fermions—First results from SESAM
First results of a recently started simulation of full QCD with two flavours
of sea-quarks at a coupling of on a lattice are
presented. Emphasis is laid on the statistical significance that can be
achieved by an ``integrated luminosity'' of 140 TFlophrs, for Hybrid
Monte Carlo simulations at four intermediate values of
. The simulation takes place on the Quadrics QH2 at
DESY/Zeuthen and DFG/Bielefeld. The performance is optimized by means of
BiCGStab and the chronological inversion method of Brower et al. We discuss the
systematic errors arising from lack of the molecular dynamic's reversibility on
the 32-bit QH2. For plaquette and meson correlators we find integrated
autocorrelation times of units of molecular dynamics time and
exponential autocorrelation times of about units. Using these results we
perform preliminary measurements of the central potential and and
correlators on independent configurations and obtain first estimates of the
lattice spacings at three values of the dynamical hopping parameter.Comment: Contributions by Th.Lippert and H.Hoeber to LAT95, Melbourne, July
1995. 8 pages, 1 ps-file, tar-compressed and uuencode