Investigations in non-perturbative QCD

Abstract

In this thesis we review two methods for studying the non-pertubative region of QCD: the effective field theory, chiral perturbation theory (χPT), and the cloudy bag model, a successful chiral quark model of hadron structure. We use information from both of these sources to construct a simple extrapolation formula in the pion mass, mπ, for the nucleon electromagnetic form factors, which combines the correct non-analytic chiral behaviour predicted by (χPT), with the correct large mπ behaviour. This formula is applied to recent quenched lattice QCD results to extrapolate to the physical regime. Given the simple nature of the extrapolation scheme, our results compare surprisingly well with experiment. We also employ a simple chiral quark model (the hedgehog) to examine the volume and pion mass dependence of the axial coupling constant, ga, along with the hedgehog baryon mass. Our results for ga reveal large volume dependence at low pion masses.