9,976 research outputs found
Casimir scaling or flux counting?
Potentials between two static sources in various representations of the SU(3)
gauge group are determined on anisotropic 3+1 dimensional lattices. Strong
evidence in favour of "Casimir scaling" is found.Comment: 4 pages Latex, epscrc2.sty with 2 epsf figure
Are there short distance non-perturbative contributions to the QCD static potential?
We find that perturbation theory fails to describe the short range static
potential as obtained from quenched lattice simulations, at least for source
separations r > 1/(6 GeV). The difference between the non-perturbatively
determined potential and perturbation theory at short distance is well
parameterised by a linear term with a slope of approximately 1.2 GeV^2 that is
significantly bigger than the string tension, sigma = 0.21 GeV^2Comment: 11 pages Latex, elsart style with 3 epsf figures, some figures and
formulas have changed due to a sign error in the original manuscript, Title
changed, typos corrected, references update
String breaking
We numerically investigate the transition of the static quark-antiquark
string into a static-light meson-antimeson system. Improving noise reduction
techniques, we are able to resolve the signature of string breaking dynamics
for Nf=2 lattice QCD at zero temperature. We discuss the lattice techniques
used and present results on energy levels and mixing angle of the static
two-state system. We visualize the action density distribution in the region of
string breaking as a function of the static colour source-antisource
separation. The results can be related to properties of quarkonium systems.Comment: 8 pages, Talk given at the Workshop on Computational Hadron Physics,
Nicosia, Cyprus, 14--17 September 200
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Where do perturbative and non-perturbative QCD meet?
We computed the static potential and Wilson loops to in
perturbation theory for different lattice quark and gluon actions. In general,
we find short distance lattice data to be well described by ``boosted
perturbation theory''. For Wilson-type fermions at present-day quark masses and
lattice spacings agreement within 10% between measured ``-shifts'' and
those predicted by perturbation theory is found. We comment on prospects for a
determination of the real world QCD running coupling.Comment: 3 pages, 4 figures, Talk at Lattice 2001 in renormalisation and
improvement sessio
The Running Coupling from SU(3) Gauge Theory
We present high precision results on the static quark-antiquark-potential on
32^4 and smaller lattices, using the standard Wilson action at BETA = 6.0, 6.2,
6.4, and 6.8 on the Connection Machine CM-2. Within our statistical errors (1%)
we did not observe any finite size effects affecting the potential values, on
varying the spatial lattice extent from 0.9 fm up to 3.3 fm. We find violations
of asymptotic scaling in the bare coupling up to BETA = 6.8. We demonstrate
that scaling violations on the string tension can be considerably reduced by
introducing effective coupling schemes, which allow for a safer extrapolation
of LAMBDA_Lattice to its continuum value. We are also able to see and to
quantify the running of the coupling from the interquark force. From this we
extract the ratio \sqrt{SIGMA}/LAMBDA_L. Both methods yield consistent values
for the LAMBDA-parameter: LAMBDA_MSbar = 0.558(-0.007+0.017)\sqrt{SIGMA}
= 246(-3+7) MeV.Comment: (Talk G. Bali at Lattice 92, Amsterdam), 4 Pages, 4 Postscript
figures, LaTeX with espcrc2, and epsf style file
Field distributions in heavy mesons and baryons
Field distributions generated by static quark-antiquark and QQQ sources are
calculated analytically in the framework of the Field Correlator Method (FCM)
using Gaussian (bilocal) correlator. In both cases the string consists mostly
of longitudinal color electric field, while transverse electric field
contributes locally less then 3%, in agreement with earlier lattice studies. In
the QQQ case the profile of the Y shape was calculated for the first time and
found to have a complicated structure with a deep well at the string junction
position. Possible consequences of this form for the baryon structure are
discussed.Comment: LaTeX2e, 11 pages, 4 Postscript figures, 2 GIF images, version to
appear in Physics Letters
Recent Developments in Lattice QCD
Recent trends in lattice QCD calculations and latest results are reviewed,
with particular emphasis on multiquark-states and the nucleon structure.Comment: Plenary Talk presented at European Few Body 19, 23-27 August 2004,
Groningen, 7 pages, 4 figure
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