Fri·Oct 21, 2005Friday·October 21, 2005

1. 01*

   Operator product expansion and quark condensate from LQCD in coordinate space

   V.Gimenez🇪🇸 · V.Lubicz🇮🇹 · F. Mescia🇮🇹 · V.Porretti🇮🇹 · J.Reyes🇮🇹

   We perform an exploratory study of the operator product expansion of the quark propagator on the lattice at short distance in coordinate space. This permits a simple determination of the quark condensate, <qq>^MS(2 GeV)=(-265\pm 5\pm 22 MeV)^3, and of the renormalization constant of the quark field, Z^MS(2 GeV)=0.871 \pm 0.003 \pm 0.020. This new method also provides a remarkable non-perturbative test of the OPE predictions at short distance in QCD.

   hep-latPoS(2006)·4 citations
2. 02*

   Perturbative renormalization of the first moment of structure functions for domain-wall QCD

   Stefano Capitani🇦🇹

   Using the domain-wall formulation of lattice fermions, we have computed the one-loop renormalization factors of one-link operators which measure the first nontrivial moment of the unpolarized, polarized and transversity structure functions, in the flavor nonsinglet sector. The knowledge of these factors is necessary in order to extract physical numbers from domain-wall Monte Carlo simulations of parton distributions. We have automated the perturbative calculations by developing suitable FORM codes. The results show that in many instances the total renormalization factors are almost equal to one, and that hence the corresponding operators are, for the appropriate values of the Dirac mass $M$ and the coupling $g_0$, practically unrenormalized.

   hep-latPRD(2006)·9 citations
3. 03*

   Cutoff effects of Wilson fermions in the absence of spontaneous chiral symmetry breaking

   Michele Della Morte🇩🇪 · Magdalena Luz🇩🇪

   We simulate two dimensional QED with two degenerate Wilson fermions and plaquette gauge action. As a consequence of the Mermin-Wagner theorem, in the continuum limit chiral symmetry is realized a la Wigner. This property affects also the size of the cutoff effects. That can be understood in view of the fact that the leading lattice artifacts are described, in the continuum Symanzik effective theory, by chirality breaking terms. In particular, vacuum expectation values of non-chirality-breaking operators are expected to be O(a) improved in the chiral limit. We provide a numerical confirmation of this expectation by performing a scaling test.

   hep-latPLB(2006)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.