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Bruneault, Mathieu

University of British Columbia

Ab initio nuclear physics considers the problem of solving the many-body Schrödinger equation for protons and neutrons in a nucleus. Of the problems that arise in trying to solve this problem, the sheer size of the Hamiltonians that need to be diagonalized has been particularly limiting in trying to derive nuclear properties from the ground up. With recent advances in computational power, and by using the in-medium similarity renormalization group, a novel ab initio approach, computations of ab initio nuclear properties are now within reach. A problem of particular interest is the scattering of nuclei by weakly interacting massive particles. As one of the prime candidates for the origin of dark matter, weakly interacting massive particles have been the subjects of many direct detection experiments. Such experiments look for nuclear recoil events caused by the non-relativistic scattering of dark matter particles off nuclei, and require careful nuclear calculations of observables such as recoil rates. In this dissertation, we present the results of ab initio calculations in the form of nuclear response functions and observables for dark matter-nucleus scattering in 22 experimentally relevant nuclei. This analysis uses the Chiral effective field theory framework to derive nuclear interactions, and the non-relativistic effective field theory framework to derive observables from a general dark matter-nucleus interaction. This approach, coupled with the in-medium similarity renormalization group, allows for ab initio calculations in quite heavy nuclei, in particular in this work we consider isotopes of Xenon, among other elements. We find that while individual nuclear responses can vary quite a lot from phenomenological calculations, overall observables remain mostly unchanged. One improvement we report on is a quantification of theoretical uncertainty, which may not be obtained from phenomenological calculations.

Text

2023-06-26

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/85150

Physics

University of British Columbia

UBCV

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