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Title: Probing the structure and size of dark matter couplings at the Large Hadron Collider
Author: Hibbs, Anthony
ISNI:       0000 0004 6498 4416
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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The mystery of dark matter (DM) is undeniably one of the greatest in modern physics. For decades, evidence has accumulated from astrophysical and cosmological experiments suggesting that the Universe contains a large amount of mass yet unaccounted for. In particular, present research indicates that approximately 84% of the total matter content in the Universe is non-baryonic DM. Together with the well-known limitations of the Standard Model of particle physics (SM), some of which could be remedied by theories which necessarily include additional particles, a particle physics solution to the DM problem is certainly well motivated. In this thesis the Large Hadron Collider (LHC) phenomenology of three models of DM is studied. In particular, the focus is on signals due to final states containing hadronic jets in association with a large amount of missing transverse energy, corresponding to DM which escapes detection. For the first model, it is found that studying events with one jet in the final state can allow constraints to be derived on the size of the couplings between DM and SM particles, but it is not possible to extract any information about the structure of the couplings. This motivates an analysis of events which feature two jets. For the second model, it is found that measurements of the azimuthal angular separation of these jets lead to contrasting distributions depending on the Lorentz structure of the interactions. These spectra are shown to be stable under various corrections and, more importantly, are clearly produced whether or not one performs the calculation using an effective field theory framework. For the third model, which differs from the first two in that DM now couples to the SM gauge bosons rather than the quarks, recent experimental searches are used to derive bounds on the fiducial cross sections for a variety of final states featuring missing transverse energy. This facilitates a comparison to be made between the various search strategies, identifying which of these most strongly constrain the operators under consideration. Considering the final state containing two jets, the azimuthal angular distributions are then plotted and are again found to be strongly dependent on the Lorentz structure of the underlying interactions. Prospects for the 14 TeV LHC run are then studied and it is found that a clear distinction between the spectra should be possible once 300 fb-1 has been collected.
Supervisor: Haisch, Ulrich Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Theoretical Physics