By combining the constraints of charge symmetry with new chiral extrapolation techniques and recent low mass lattice QCD simulations of the individual quark contributions to the magnetic moments of the nucleon octet, we obtain a precise determination of the strange magnetic moment of the proton. The result, namely G s M = −0.046 ± 0.019 µN , is consistent with the latest experimental measurements but an order of magnitude more precise. This poses a tremendous challenge for future experiments.

We study the scaling behavior of the quark propagator on two lattices with similar physical volume in Landau gauge with 2+1 flavors of dynamical quarks in order to test whether we are close to the continuum limit for these lattices. We use configurations generated with an improved staggered ("Asqtad") action by the MILC collaboration. The calculations are performed on 28 3 × 96 lattices with lattice spacing a = 0.09 fm and on 20 3 × 64 lattices with lattice spacing a = 0.12 fm. We calculate the quark mass function, M (q 2 ), and the wave-function renormalization function, Z(q 2 ), for a variety of bare quark masses. Comparing the behavior of these functions on the two sets of lattices we find that both Z(q 2 ) and M (q 2 ) show little sensitivity to the ultraviolet cutoff.

The electromagnetic properties of the baryon octet are calculated in quenched QCD on a 20 3 × 40 lattice with a lattice spacing of 0.128 fm using the fat-link irrelevant clover (FLIC) fermion action. FLIC fermions enable simulations to be performed efficiently at quark masses as low as 300 MeV. By combining FLIC fermions with an improved-conserved vector current, we ensure that discretisation errors occur only at O(a 2 ) while maintaining current conservation. Magnetic moments and electric and magnetic radii are extracted from the electric and magnetic form factors for each individual quark sector. From these, the corresponding baryon properties are constructed. Our results are compared extensively with the predictions of quenched chiral perturbation theory. We detect substantial curvature and environment sensitivity of the quark contributions to electric charge radii and magnetic moments in the low quark mass region. Furthermore, our quenched QCD simulation results are in accord with the leading non-analytic behaviour of quenched chiral perturbation theory, suggesting that the sum of higher-order terms makes only a small contribution to chiral curvature.