Renormalisation of Composite Operators in Lattice Perturbation Theory with Clover Fermions: Non-forward Matrix Elements

We consider the renormalisation of lattice QCD operators with one and two covariant derivatives related to the first and second moments of generalised parton distributions and meson distribution amplitudes. Employing the clover fermion action we calculate their non-forward quark matrix elements in one-loop lattice perturbation theory. For some representations of the hypercubic group commonly used in simulations we determine the sets of all possible mixing operators and compute the matrices of renormalisation factors in one-loop approximation. We describe how tadpole improvement is applied to the results.Comment: 16 pages; v2: eqs.(27), (28), (74)-(79) corrected, several signs changed in section III.

Three-point functions in noncompact lattice QED

We calculate fermion-antifermion-"meson" three-point functions in noncompact lattice QED with dynamical staggered fermions and use them to extract effective Yukawa couplings. The results are consistent with the hypothesis that QED is trivial.Comment: Latex article. 3 pages, ps file. Contribution to LAT93, Dallas, U.S.A. HLRZ preprint 93-7

One-loop renormalisation for the second moment of GPDs with Wilson fermions

We calculate the non-forward quark matrix elements for operators with two covariant derivatives in one-loop lattice perturbation theory using Wilson fermions. These matrix elements are needed in the renormalisation of the second moment of generalised parton distributions measured in lattice QCD. For some commonly used representations of the hypercubic group we determine the sets of all mixing operators and find the matrices of mixing and renormalisation factors.Comment: Lattice 2004(improved), 3 pages, LaTeX style file, espcrc2.sty include

Resolution of the Landau pole problem in QED

We present new numerical results for the renormalized mass and coupling in non-compact lattice QED with staggered fermions. Implications for the continuum limit and the role of the Landau pole are discussed.Comment: 3 pages, talk presented by H. St\"uben at Lattice '97, Edinburg

Seeking the Equation of State of Non-Compact Lattice QED

We perform a high statistics calculation of the equation of state for non-compact QED on large lattices. The calculation extends to fermionic correlation lengths of $\approx 8$, and it is combined with a finite size scaling analysis of the lattice data.Comment: 32 pages, uuencoded Z-compressed postscript file. Also available from http://www.desy.de/pub/preprints/desy/1996

Gauge theories with overlap fermions in an arbitrary representation: Evaluation of the 3-loop beta-function

This work presents the calculation of the relation between the bare coupling constant g_0 and the MSbar-renormalized coupling g_MS, g_0 = Z_g(g_0,a\mu) g_MS, to 2 loops in perturbation theory, with fermions in an arbitrary representation of the gauge group SU(N). Our calculation is performed using overlap fermions and Wilson gluons, and the background field technique has been chosen for convenience. The corresponding results in the fundamental representation appear in our longer publication [arXiv:0709.4368]. The 3-loop coefficient of the bare beta-function, b_2^L, is extracted using the 2-loop expression for Z_g, and it is presented as a function of the overlap parameter rho, the number of fermion flavors (N_f) and the number of colors (N). We also provide the expression for the ratio Lambda_L/Lambda_MS, in an arbitrary representation. A plot of Lambda_L/Lambda_MS is given in the adjoint representation.Comment: 15 pages, 5 figure

Generalized parton distributions and structure functions from full lattice QCD

We present here the latest results from the QCDSF collaboration for (moments of) structure functions and generalized form factors in full QCD with Nf=2 O(a)-improved Wilson fermions based on simulations closer to the chiral and continuum limit.Comment: Talks presented by D.Pleiter and J.Zanotti at Lattice2004(weak), Fermilab, June 21-26, 2004, 6 pages, 9 figure

Lattice Renormalization of Quark Operators

We have technically improved the non-perturbative renormalization method, proposed by Martinelli et al., by using quark momentum sources and sinks. Composite two-fermion operators up to three derivatives have been measured for Wilson fermions and Sheikholeslami-Wohlert improved fermions in the quenched approximation. The calculations are performed in the Landau gauge on 16^3x32 lattices at beta = 6.0 for 3 kappa values in each case. The improved sources greatly decrease the statistical noise. We extract and discuss here renormalization factors for local operators and moments of the structure functions for Wilson fermions.Comment: 3 pages, Latex, 6 figures. epsf.sty and espcrc2.sty needed. Talk given at Lattice9

Perturbative renormalization of bilinear quark and gluon operators

The renormalisation constants for local bilinear quark operators are calculated using the Sheikholeslami-Wohlert improved action. In addition we compute the renormalisation constant of the leading gluon operator for different group representations and discuss the mixing of the operators E^2 and B^2.Comment: 3 pages, poster contributed at Lattice96, St. Loui