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Adair, Connor

University of British Columbia

The existence of a CP violating θ term in the QCD Lagrangian and the smallness of that term (θ < 10⁻¹⁰) is known as the Strong CP problem and is an unresolved problem in particle physics. The most favoured solution to the strong CP problem is the Peccei-Quinn mechanism which introduces an additional U(1) symmetry. When this symmetry is spontaneously broken a pseudo-goldstone boson called the axion is produced. Cosmological studies of the axion have shown that it may be produced in abundances through the oscillation of the axion field in the early universe (called the misalignment mechanism) and so can be a source of dark matter. This led to the development of axion haloscopes to search for these axions. Standard axion searches rely on resonant cavities in a strong magnetic field. These axions are thought to be virialized and non-relativistic, this leads to them having a frequency with a small linewidth (on the order of kHz). To detect these axions the cavities must be tuned in discrete steps. In this thesis we will discuss a different method to search for axions based on broadband search ideas. Specifically we will focus on relativistic axions which can be produced under a variety of models. This means that line width of axions from relativistic models will be large (∼ 1 GHz) and this will require a new detection strategy. We will discuss new methods for detecting broadband axions including a search for daily modulations which, up until now, have been ignored in the literature. The idea is to collect the signal over an entire season during a specific hour and fit the resulting power excess as a function of time (measured in hours) during a twenty-four hour period. We will discuss how a genuine signal can be discriminated from a spurious signal and background noise by considering B=0 data and by studying the phase drift of the daily modulations. Finally we will comment on how these broadband searches may be applied to current axion cavity experiments.

Text

2024-01-25

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87378

Physics

University of British Columbia

UBCV

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