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Leinweber, Derek Thomas, Anthony Abell, Curtis David School of Physics, Chemistry and Earth Sciences 2023 https://hdl.handle.net/2440/139724 Hamiltonian Effective Field Theory (HEFT) is a non-perturbative extension of effective field theory which provides a bridge between the infinite-volume scattering data of ex- periment, and finite-volume energy spectra from lattice QCD. By discretising a Hamilto- nian which has been constrained to experimental scattering data, solving the eigenvalue equation for the Hamiltonian provides a finite-volume energy spectrum, which may be compared with lattice QCD eigenstates. In addition, eigenvectors of the Hamiltonian pro- vide insight into the structure of these eigenstates. This matrix Hamiltonian has been made finite by finite-range regularisation, and by considering the range of regularisation parameters which allow the Hamiltonian to describe experimental scattering data, insight is gained into the degree of model-dependence in the infinite-volume and finite-volume quantities. This formalism is extended for the first time to systems with multiple quark- model like baryon states. By considering the effect of a second bare basis state on both the infinite-volume poles, and finite-volume energy spectrum, we gain a unique intuition into the relationship between these two regimes. Finally, we apply the multiple bare-baryon formalism to the odd-parity nucleon sector. We find that the interpretation of the two odd-parity nucleons as three-quark cores dressed by πN , ηN , and KΛ two-particle states is consistent with both the experimental scattering data, and lattice QCD results at three lattice volumes. We also introduce a novel HEFT simulation of lattice QCD correlation functions, allowing for a determination of the two-particle scattering-state contamination in lattice QCD eigenstates. Thesis (Ph.D.) -- University of Adelaide, School of Physics, Chemistry and Earth Sciences, 2023 en baryon resonances effective field theory scattering finite-volume The Structure of Baryon Resonances Thesis This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legalsopen.access