John W. Negele

Learn More
We present the resolution of a long-standing discrepancy between the moments of parton distributions calculated from lattice QCD and their experimental values. We propose a simple extrapolation formula for the moments of the nonsinglet quark distribution u-d, as a function of quark mass, which embodies the general constraints imposed by the chiral symmetry(More)
Since present Monte Carlo algorithms for lattice QCD may become trapped in a fixed topological charge sector, it is important to understand the effect of calculating at fixed topology. In this work, we show that although the restriction to a fixed topological sector becomes irrelevant in the infinite volume limit, it gives rise to characteristic finite size(More)
  • Lhpc Collaboration, R G Edwards, +7 authors W Schroers
Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea(More)
In contrast to ensembles of singular gauge instantons, which are well known to fail to produce confinement, it is shown that effective theories based on ensembles of merons or regular gauge instantons do produce confinement. Furthermore, when the scale is set by the string tension, the action density, topological susceptibility, and glueball masses are(More)
Cooling is used as a lter on a set of gluon elds sampling the Wilson action to selectively remove essentially all uctuations of the gluon eld except for the instantons. The close agreement between quenched lattice QCD results with cooled and uncooled conngurations for vacuum correlation functions of hadronic currents and for density-density correlation(More)
This initiative will use large-scale numerical simulations to solve QCD, the fundamental theory governing strong interactions, to understand the structure and interactions of hadrons. Jefferson Lab and MIT will develop, build, and operate cost-optimized QCD Alpha Cluster computers using commodity components. These 256-processor and 64-processor clusters(More)
Generalized parton distributions encompass a wealth of information concerning the three-dimensional quark and gluon structure of the nucleon, and thus provide an ideal focus for the study of hadron structure using lattice QCD. The special limits corresponding to form factors and parton distributions are well explored experimentally, providing clear tests of(More)
This work presents the first calculation in lattice QCD of three moments of spin-averaged and spin-polarized generalized parton distributions in the proton. It is shown that the slope of the associated generalized form factors decreases significantly as the moment increases, indicating that the transverse size of the light-cone quark distribution decreases(More)