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Gysbers, Peter

University of British Columbia

Atomic nuclei exhibit many phenomena not limited to excited states, decays, reactions, and clustering. Nuclear processes control the evolution of stars and explain the abundances of chemical elements in the universe. Nuclear physics can be used to answer fundamental questions about underlying particle physics and cosmology, such as the symmetry between matter and antimatter or the nature of neutrinos. The discrepancy between theoretical predictions and observations motivates improved theory and can provide evidence for new physics. A predictive model of nuclei is needed as input for experimental tests and for astrophysical models. Nuclei are complex strongly-interacting quantum many-body systems. Accurate the- oretical techniques are required to predict the rate of nuclear decay processes, the cross section of nuclear reactions and the distribution of the emitted particles. Ab initio nuclear theory takes advantage of the recent rapid increase in computing power to calculate nuclear structure and reactions solely from realistic interactions between the constituent nucleons. In this thesis, we first present beta-decay calculations using the ab initio no-core shell model. Our calculations provide an explanation for the quenching of Gamow-Teller beta- decays, provide nuclear structure corrections to the beta-spectrum necessary to interpret experiments seeking to find new physics and provide estimates for the hypothetical process of neutrinoless double-beta decay. Second, we present radiative capture calculations using the no-core shell model with continuum, an extension which places bound and scattering states on equal footing. The rate of radiative capture reactions in big bang nucleosynthesis is required to estimate the abundance of isotopes in the early universe. In addition, anomalies in recent radiative capture experiments claim the discovery of a new boson. Comparing to these experiments requires prediction of the distribution of electron-positron pairs produced by radiative capture.

Text

2023-03-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84112

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/