Generalized parton distributions and nucleon structure at large x from lattice QCD

Recent progress in lattice calculations of generalized parton distributions is discussed, with emphasis on the large-x behavior of nucleon structure functions. (orig.)Available from TIB Hannover: RA 2999(04-212) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Glueball and gluelump spectrum in abelian projected QCD

We study glueball and gluelump spectra calculated after abelian projection in both quenched and N_f = 2 full QCD. The abelian projection is made after MA gauge fixing. We demonstrate that both spectra can be recovered despite the problem with positivity. We suggest the interpretation of some of the gluelump states in the language of the abelian projected theory. (orig.)Available from TIB Hannover: RA 2999(01-168) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Separating perturbative and non-perturbative contributions to the plaquette

We try to separate the perturbative and non-perturbative contributions to the plaquette of pure SU(3) gauge theory. To do this we look at the large-n asymptotic behaviour of the perturbation series in order to estimate the contribution of the as-yet uncalculated terms in the series. We find no evidence for the previously reported #LAMBDA#"2 contribution to the gluon condensate. Attempting to determine the conventional #LAMBDA#"4 condensate gives a value #propor to#0.03(2) GeV"4, in reasonable agreement with sum rule estimates, though with very large uncertainties. (orig.)Available from TIB Hannover: RA 2999(01-166) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Low-lying fermion modes of N_f=2 improved Wilson fermions

We present preliminary results for the topological charge and susceptibility determined from the low-lying eigenmodes of the Wilson-Dirac operator. These modes have been computed on dynamical configurations with N_f=2 non-perturbatively improved Wilson fermions. We compare our results with the eigenmodes of fermions in the quenched approximation. (orig.)Available from TIB Hannover: RA 2999(01-167) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The spin structure of the #LAMBDA# hyperon in quenched lattice QCD

It has been suggested to use the production of #LAMBDA# hyperons for investigating the nucleon spin structure. The viability of this idea depends crucially on the spin structure of the #LAMBDA#. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have studied matrix elements of two-quark operators in the #LAMBDA#. We present results for the axial vector current, which give us the contributions of the u, d, and s quarks to the #LAMBDA# spin. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(010144) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Progress towards a lattice determination of (moments of) nucleon structure functions

Using unimproved and non-perturbatively O(a) improved Wilson fermions, results are given for the three lowest moments of unpolarised nucleon structure functions. Renormalisation, chiral extrapolation and the continuum limit of the matrix elements are briefly discussed. The simulations are performed for both quenched and two flavours of unquenched fermions. No obvious sign of deviation from linearity in the chiral extrapolations are found. (This is most clearly seen in our quenched unimproved data, which extends to lighter quark mass). Possible quenching effects also seem to be small. The lowest moment thus remains too large, so it seems to be necessary to reach smaller quark masses in numerical simulations. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(01-169) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Finite temperature QCD with two flavors of dynamical quarks on 24"3 x 10 lattice

We present results obtained in QCD with two flavors of non-perturbatively improved Wilson fermions at finite temperature on 16"3 x 8 and 24"3 x 10 lattices. We determine the transition temperature in the range of quark masses 0.6 < m_#pi#/m_#rho# < 0.8 at lattice spacing a#approx#0.1 fm and extrapolate the transition temperature to the continuum and to the chiral limits. (orig.)SIGLEAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Profiles of the broken string in two-flavor QCD below and above the finite temperature transition

We study the Abelian flux tube profile of mesonic and the baryonic configurations of static quarks below and above the finite-temperature transition in N_f = 2 full QCD. To reduce effects of ultra-violet fluctuations we measure Abelian distributions of the action density, the color-electric field and the monopole current after fixing to the maximally Abelian gauge. Changing the distance R between quarks for fixed T/T_c < 1, one can see a clear signal of string breaking for large R. The electric field becomes Coulomb-like and the circulating monopole current disappears. We study also the temperature dependence of the flux profile for fixed R #approx# 0.7 fm. The disappearance of the squeezed flux is observed clearly above T_c. Similar behaviors are observed both in the mesonic and the baryonic systems. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(04-005) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Structure of the baryonic flux tube in N_f=2 lattice QCD at finite temperature

We study the flux tube profile in the baryonic system in full QCD at finite temperature of N_t=8 lattice. We fix the maximally Abelian gauge and measure the monopole and the photon parts of the Abelian action density, the color electric field and the monopole current on both sides of the finite temperature transition. We demonstrate the disappearance of the flux tube in the high temperature phase. (orig.)Available from TIB Hannover: RA 2999(03-144) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A lattice determination of moments of unpolarised nucleon structure functions using improved Wilson fermions

Within the framework of quenched lattice QCD and using O(a) improved Wilson fermions and non-perturbative renormalisation, a high statistics computation of low moments of the unpolarised nucleon structure functions is given. Particular attention is paid to the chiral and continuum extrapolations. (orig.)SIGLEAvailable from TIB Hannover: RA2999(04-194) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman