QCD Phenomenology of Heavy Particle Dynamics

Abstract: In this thesis the phenomenology of Quantum Chromo Dynamics (QCD) is studied in a variety of circumstances from both perturbative and non-perturbative perspectives. The main emphasis is on the production and hadronization of heavy particles, specifically heavy quarks, gauge bosons, leptoquarks and supersymmetric particles. In the hadroproduction of long-lived heavy quarks (i.e. charm and bottom) in the context of string fragmentation, the pull of a beam remnant at the other end of a string may give a heavy hadron more energy than the perturbatively produced quark. The collapse of a low-mass string to a single hadron is the extreme case of this effect, and gives rise to asymmetries between hadron and anti-hadron spectra. The Lund string fragmentation model is studied and improved by considering fixed-target data and the model is then used to predict the outcome of future experiments. The describtion of QCD radiation off heavy quarks and supersymmetric coloured particles is improved by using matrix element corrections to the massless parton shower in the event generator PYTHIA. In the process e+e- -> W+W- -> q qbar q' qbar', the colour flow can be ambiguous and a transverse momentum based measure of the colour flow is investigated as a tool to determine string topologies. The method is used to study different models of colour reconnection. QCD aspects of leptoquark production at HERA are discussed with focus on initial- and final-state QCD radiation. By taking into account corrections to this in mass reconstructions of a leptoquark, a narrower mass peak and a better average mass value is obtained.