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Title: An investigation of hadron mass calculations in lattice QCD
Author: Collins, Sara
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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In this thesis I study Quantum Chromodynamics on the lattice. This formulation of QCD allows for a first-principles calculation of the hadron mass spectrum. Comprehensive agreement with experiment has yet to be achieved, and this is due in part to the difficulties of isolating the ground state mass from the spectrum of excited states created using an interpolating field on the lattice. In the first chapter, after briefly introducing the standard Wilson action for lattice QCD, and the improved clover action with reduced discretisations errors, the standard techniques for extracting hadron masses are reviewed. In the second chapter I present two new methods for the extraction of hadron masses using a combination of two operators with the same quantum numbers to isolate the ground and first excited states. I apply these two methods to the low-lying hadron states and compare the results with existing methods for extracting the first excited state. Conventionally the Wilson and clover actions are assumed to be inappropriate for the simulation of hadrons containing one or more quarks with Compton wave-lengths shorter than twice the lattice spacing. The discretisation errors for both actions are expected to diverge in this limit. In chapter three I discuss a proposal that actions of this type are suitable for non-relativistic QCD. This proposal suggests a continuum non-relativistic dispersion relation for hadrons containing heavy quarks, parameterised by two mass scales. A dispersion relation of this form is tested against the finite-momentum behaviour of the pseudoscalar mesons containing one or more heavy quarks. The effects of using the different mass parameters to fix the physical quark mass on the predictions for the pseudoscalar and vector decay constants are studied, and this analysis is extended to the mass splittings in the mesons containing one or more heavy quarks in chapter four.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available