126 research outputs found
Non-Perturbative versus Perturbative Renormalization of Lattice Operators
Our objective is to compute the moments of the deep-inelastic structure
functions of the nucleon on the lattice. A major source of uncertainty is the
renormalization of the lattice operators that enter the calculation. In this
talk we compare the renormalization constants of the most relevant twist-two
bilinear quark operators which we have computed non-perturbatively and
perturbatively to one loop order. Furthermore, we discuss the use of tadpole
improved perturbation theory.Comment: 4 pages, uuencoded postscript file. Contribution to Lattice 95. Also
available from http://www.desy.de/pub/preprints/desy/199
A Lattice Evaluation of the Deep-Inelastic Structure Functions of the Nucleon
The lower moments of the unpolarized and polarized deep-inelastic structure
functions of the nucleon are calculated on the lattice. The calculation is done
with Wilson fermions and for three values of the hopping parameter , so
that we can perform the extrapolation to the chiral limit. Particular emphasis
is put on the renormalization of lattice operators. The renormalization
constants, which lead us from lattice to continuum operators, are computed
perturbatively to one loop order as well as non-perturbatively.Comment: 11 pages, uuencoded postscript file. Talk given at Workshop QCD on
Massively Parallel Computers, Yamagata, March 1995. Also available from
http://www.desy.de/pub/preprints/desy/199
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
The Drell-Yan process and Deep Inelastic Scattering from the lattice
We report on measurements of the h_1 structure function, relevant to
calculating cross-sections for the Drell-Yan process. This is a quantity which
can not be measured in Deep Inelastic Scattering, it gives additional
information on the spin carried by the valence quarks, as well as insights on
how relativistic the quarks are.Comment: 3 pages, Latex, 3 figures, espcrc2.sty included, Talk presented at
LATTICE96(phenomenology
First results with non-perturbative fermion improvement
We present initial results for light hadron masses and nucleon structure
functions using a recent proposal for eliminating all effects from
Wilson fermion simulations in the quenched approximation. With initially
limited statistics, we find a much more linear APE plot and a value of the
axial coupling nearer to the experimental point than with comparable runs
using unimproved Wilson fermions.Comment: 3 pages, 2 PostScript figures, LaTeX 2.09 with espcrc2.sty v2.6,
amstex and epsf, talk presented at LATTICE96(phenomenology) by P. Stephenso
Improvement for Quenched Wilson Fermions
We briefly describe some of our recent results for the mass spectrum and
matrix elements using improved fermions for quenched QCD. Where possible
a comparison is made between improved and Wilson fermions.Comment: 6 pages, Latex, 11 figures, epsf.sty and buckow1.sty needed
(buckow1.sty included). Talk presented at the 31st Ahrenshoop Symposium on
the Theory of Elementary Particles, September 1997, Buckow, German
Non-perturbative improvement and renormalization of lattice operators
The Alpha Collaboration has proposed an optimal value for c_SW in the
Sheikholeslami-Wohlert action, chosen to remove O(a) effects. To measure
hadronic matrix elements to the same accuracy we need a method of finding O(a)
improved operators, and their renormalization constants. We determine the Z
factors by a non-perturbative method, measuring the matrix elements for single
quark states propagating through gauge fields in the Landau gauge. The data
show large effects coming from chiral symmetry breaking. This allows us to find
the improvement coefficients too, by requiring that the amount of chiral
symmetry breaking agrees with that predicted by the chiral Ward identities.Comment: 3 pages, Latex, 2 figures, epsf.sty and espcrc2.sty needed. Talk
given at Lattice9
Improvement of Nucleon Matrix Elements
We report on preliminary results of a high statistics quenched lattice QCD
calculation of nucleon matrix elements within the Symanzik improvement
programme. Using the recently determined renormalisation constants from the
Alpha Collaboration we present a fully non-pertubative calculation of the
forward nucleon axial matrix element with lattice artifacts completely
removed. Runs are made at and , in an attempt to check
scaling and effects. We shall also briefly describe results for ,
the matrix element of a higher derivative operator.Comment: 3 pages, Latex, 4 figures, epsf.sty and espcrc2.sty needed, Talk
given at LATTICE97. Figure 4 correcte
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