Detecting WIMPs, neutrinos and axions in the next generation of dark matter experiment

O'Hare, Ciaran A. J. (2017) Detecting WIMPs, neutrinos and axions in the next generation of dark matter experiment. PhD thesis, University of Nottingham.

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The first direct detection of dark matter is anticipated in coming years by one of a range of experimental strategies. Because the identity of dark matter remains unknown, the strategy that will be successful in this one cannot say. However beneath this fundamental particle physics uncertainty lies another uncertainty with regard to the structure of the dark matter halo of the Milky Way that must be confronted when interpreting data from terrestrial experiments. However these astrophysical uncertainties might only be resolved with the very same experiments; in fact, directly detecting dark matter represents the only way to probe the ultralocal structure of the halo. This thesis explores the impact of astrophysical uncertainties on the particle physics goals of dark matter detection but also the extent to which we might in the future be able to resolve those uncertainties. The discussion is framed around the detection of three types of particle, two of which are dark matter candidates: weakly interacting massive particles (WIMPs), neutrinos and axions.

In the case of WIMPs I consider how upcoming directionally sensitive experiments can be used to probe the full 3-dimensional velocity distribution to learn about dark matter substructure. A range of model dependent and independent statistical approaches are tested under various astrophysical benchmarks. I also explore prospects for WIMP direct detection when faced with the ultimate neutrino background, as expected in the next generation of experiment. In this eventuality the uncertainties in the neutrino flux are essential in predicting the WIMP models inaccessible due to the background. However the same is true of astrophysical uncertainties. Once astrophysical uncertainties are accounted for the neutrino floor limit is raised in cross section by up to an order of magnitude and the accuracy of any potential WIMP particle measurement is greatly increased. Addressing these concerns, I demonstrate how one should go about subtracting the neutrino background. This involves a return to directional detection. I find that even non-ideal circumstances, the neutrino and WIMP signals can be distinguished and the neutrino floor overcome.

Finally in the context of axions, I discuss the prospects for microwave cavity haloscope experiments to perform "axion astronomy". Haloscopes measure the direct conversion of axions into photons and hence can make potentially much finer measurements of the dark matter halo compared with WIMPs. I develop a technique to extract astrophysical parameters, such as the halo velocity dispersion and laboratory velocity, as well as learn about properties of substructure from tidal streams and axion miniclusters. I show that a level of precision can be achieved in relatively short duration haloscope experiments that can match or improve upon that of astronomical observations.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Green, Anne M.
Moss, A.J.
Keywords: Particle astrohysics, Dark matter, Neutrinos, Direct detection, Axions
Subjects: Q Science > QB Astronomy
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 42318
Depositing User: O'Hare, Ciaran
Date Deposited: 12 Jul 2017 04:40
Last Modified: 26 Oct 2017 10:10

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