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

QCD Phenomenology of Static Sources

We discuss the spectrum of open string and point particle excitations in QCD with various source representations. Some general relations are introduced and lattice results presented. In particular we discuss the short-distance behaviour, relate this to perturbation theory expectations and comment on the matching between low energy matrix elements and high energy Wilson coefficients, within the framework of effective field theories.Comment: Invited Talk presented at LightCone 2004, 16-20 August 2004, Amsterdam, 10 page

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

Non-perturbative determination of improvement coefficients using coordinate space correlators in Nf=2+1N_f=2+1 lattice QCD

We determine quark mass dependent order $a$ improvement terms of the form $b_Jam$ for non-singlet scalar, pseudoscalar, vector and axialvector currents using correlators in coordinate space on a set of CLS ensembles. These have been generated employing non-perturbatively improved Wilson Fermions and the tree-level L\"uscher-Weisz gauge action at $\beta = 3.4, 3.46, 3.55$ and $3.7$, corresponding to lattice spacings ranging from $a \approx 0.085$ fm down to $0.05$ fm. In the $N_f=2+1$ flavour theory two types of improvement coefficients exist: $b_J$, proportional to non-singlet quark mass combinations, and $\bar{b}_J$ (or $\tilde{b}_J$), proportional to the trace of the quark mass matrix. Combining our non-perturbative determinations with perturbative results, we quote Pad\'e approximants parameterizing the $b_J$ improvement coefficients within the above window of lattice spacings. We also give preliminary results for $\tilde{b}_J$ at $\beta=3.4$.Comment: 15 pages, 6 figures, version published in PR

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

The Static Potential to O(\alpha^2) in Lattice Perturbation Theory

We present a calculation of Wilson loops, and the static inter-quark potential to $O(\alpha^2)$ in lattice perturbation theory. This is carried out with the Wilson, Symanzik-Weisz, and Iwasaki gauge actions and the Wilson, Sheikholeslami-Wohlert, and Kogut-Susskind dynamical fermion action for small Wilson loops, and with the Wilson gauge action and each of the dynamical quark actions in the case of the static potential.Comment: Lattice2001(improvement) 3 pages, 3 figure

The DsJ(2317): what can the Lattice say?

We present lattice results on the scalar $D_s$ meson and comment on the $D_{sJ}^+(2317)$ state recently discovered by BaBar and confirmed by CLEO, in view of a series of theoretical claims and counter claims. Lattice predictions in the static limit indicate larger masses than observed for a scalar quark model state. Finite $c$ quark mass corrections seem to further enlarge this discrepancy, in support of a non quark-antiquark-state interpretation of experiment.Comment: 4 pages, 1 Figur