Hadron Electromagnetic Structure: Shedding Light on Models and their Mechanisms

Strange quark contributions to the proton magnetic moment are estimated from a consideration of baryon magnetic moment sum rules. The environment sensitivity of quark contributions to baryon moments is emphasized. Pion cloud contributions to proton charge radii are examined in the framework of Chiral Perturbation Theory. The absence of scalar-diquark clustering in the nucleon is discussed.Comment: Lattice '93 presentation. UU-File is a single postscript file of a 3 page manuscript including figures. Ohio State U. PP #93-112

Essential Strangeness in Nucleon Magnetic Moments

Effective quark magnetic moments are extracted from experimental measurements as a function of the strangeness magnetic moment of the nucleon. Assumptions made in even the most general quark model analyses are ruled out by this investigation. Ab initio QCD calculations demand a non-trivial role for strange quarks in the nucleon. The effective moments from QCD calculations are reproduced for a strangeness magnetic moment contribution to the proton of 0.11 $\mu_N$, which corresponds to $F_2^s(0) = -0.33\ \mu_N$.Comment: HYP '94 presentation. File is a uuencoded postscript file of a 2 page manuscript including figures. Also available via anonymous ftp from pacific.mps.ohio-state.edu in pub/NTG/Leinweber as StrQrkNmom.ps(.gz) OSU PP #94-063

Chiral Nonanalytic Behaviour: The Edinburgh Plot

The Edinburgh Plot is a scale independent way of presenting lattice QCD calculations over a wide range of quark masses. In this sense it is appealing as an indicator of how the approach to physical quark masses is progressing. The difficulty remains that even the most state of the art calculations are still at quark masses that are too heavy to apply dimensionally-regulated chiral perturbation theory. We present a method allowing predictions of the behaviour of the Edinburgh plot, in both the continuum, and on the lattice.Comment: 3 pages, 4 figures, Lattice2002(Spectrum

Over-Improved Stout-Link Smearing

A new over-improved stout-link smearing algorithm, designed to stabilise instanton-like objects, is presented. A method for quantifying the selection of the over-improvement parameter, $\epsilon$, is demonstrated. The new smearing algorithm is compared with the original stout-link smearing, and Symanzik improved smearing through calculations of the topological charge and visualisations of the topological charge density.Comment: 9 pages, 18 figures, submitted to Physical Review

Light Hadron Spectroscopy on Coarse Lattices with O(a^2) Mean-Field Improved Actions

The masses and dispersions of light hadrons are calculated in lattice QCD using an O(a^2) tadpole-improved gluon action and an O(a^2) tadpole-improved next-nearest-neighbor fermion action originally proposed by Hamber and Wu. Two lattices of constant volume with lattice spacings of approximately 0.40 fm and 0.24 fm are considered. The results reveal some scaling violations at the coarser lattice spacing on the order of 5%. At the finer lattice spacing, the calculated mass ratios reproduce state-of-the-art results using unimproved actions. Good dispersion and rotational invariance up to momenta of pa ~ 1 are also found. The relative merit of alternative choices for improvement operators is assessed through close comparisons with other plaquette-based tadpole-improved actions.Comment: 17 page RevTeX manuscript. 7 Figures. This and related papers may also be obtained from http://www.physics.adelaide.edu.au/~dleinweb/Publications.htm