2,443 research outputs found
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
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
The Static Quark-Antiquark Potential: A ``Classical'' Experiment On The Connection Machine CM-2
We describe the Wuppertal university pilot project in applied parallel
computing. We report on a comprehensive high statistics determination of the
static quark-antiquark potential and related quantities from quenched quantum
chromodynamics. New data for the string tension and the plaquette action for
the region 5.5 < beta < 6.8 is presented.Comment: (Talk K. Schilling), 11 pages, postscript (\approx 250K
SU(2) Colour Fields Around Static Sources
First results of an ongoing high statistics study of the colour flux
distribution around static quark sources in SU(2) gauge theory are presented.
The flux tube profiles and widths have been investigated for several quark
separations at beta=2.5 and beta=2.74. The results are tested against Michael's
sum rules.Comment: 3 pages (LaTeX) with 4 epsf incl. PS figs., To be publ. in Proc. of
Lattice '9
Alpha_s from the Lattice Potential
We present an extensive study on the direct determination of the running
coupling alpha_s from the static quark antiquark force at short distances, in
quenched QCD. We find from our high statistics potential analysis that alpha_qq
exhibits two-loop asymptotic behaviour for momenta as low as .5 GeV. As a
result, we determine the zero flavour Lambda-parameter to be Lambda^0_MSBAR =
0.630(38)\sqrt{\sigma} = 293(18)^{+25}_{-63} MeV. A rough estimate of full QCD
effects leads to the five flavour value alpha_MSBAR(m_Z) = .102^{+6}_{-11}. A
comparison with other lattice results is made.Comment: 6 pages (LaTeX) with 7 postscript figures (epsf required), Invited
talk by K. Schilling held at Lattice '93 conference, Dallas, T
A Ginzburg-Landau Analysis of the Colour Electric Flux Tube
In a simulation of SU(2) gauge theory we investigate, after maximal Abelian
projection, the dual Maxwell equations for colour field and monopole current
distributions around a static quark-antiquark pair Q_ Q in vacuo. Within the
dual superconductor picture we carry out a Ginzburg-Landau type analysis of the
flux tube profile. As a result we can determine the coherence length of the GL
wave function related to the monopole condensate, xi = .25(3) fm, to be
compared to the penetration length, lambda = >.15(2) fm (scaled with the string
tension).Comment: 3 pages, 5 figures, corrected typos, LATTICE98(confine
First Evidence of -Dependence in the QCD Interquark Potential
We present a lattice calculation of the interquark potential between static
quarks in a ``full'' QCD simulation with 2 flavours of dynamical Wilson-quarks
at three intermediate sea-quark masses. We work at on lattice
size of with 100 configurations per sea-quark mass. We compare
the full QCD potential with its quenched counterpart at equal lattice spacing,
GeV, which is at the onset of the quenched scaling regime.
We find that the full QCD potential lies consistently below that of quenched
QCD. We see no evidence for string-breaking effects on these lattice volumes,
.Comment: 9 pages (1 tex file epsf-style + 6 ps-figures
Color Flux Profiles in SU(2) Lattice Gauge Theory
Results of a high statistics study of chromo field distributions around
static sources in pure SU(2) gauge theory on lattices of volumes ,
, and at , , and are presented.
We establish string formation up to physical distances as large as 2 fm.Comment: Contribution to Lattice '94, 3 pages uu-compressed LaTeX + 3 psfig
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