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

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

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

"Glueballs": results and perspectives from the lattice

I review the present status of lattice calculations of properties of gluon-rich hadrons and comment on future prospects, in view of planned experiments.Comment: 4 pages, 1 Figure, Talk presented at Photon 2001, Ascona, CH, 2.9. - 7.9.0

Baryons on the lattice

I comment on progress of lattice QCD techniques and calculations. Recent results on pentaquark masses as well as of the spectrum of excited baryons are summarizned and interpreted. The present state of calculations of quantities related to the nucleon structure and of electromagnetic transition form factors is surveyed.Comment: 10 pages, Plenary talk at 10th International Conference on Structure of Baryons (Baryons 2004), Palaiseau, France, 25-29 Oct 2004, 1 reference added, minor improvement

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