Under the umbrella of Theoretical Physics, progress in ‘Beyond the Standard Model’ (BSM) physics proceeds broadly along two main avenues of investigation. The first is concerned with constructing theories that attempt to explain observations, or address theoretical problems, which cannot be explained within the tremendously successful Standard Model (SM) of particle physics. The second involves looking for new ways to observe or test BSM physics, and such tests are usually developed with current experimental hints, or attractive theoretical models, in mind. This thesis contains material which falls under both approaches. Part I is concerned with Supersymmetry (SUSY). We review the basics of SUSY, and the current state of this field, and then present a novel model for SUSY at the TeV scale. This model has a Higgs sector similar to the SM and possesses a continuous U(1)<sub>R</sub> symmetry, dramatically suppressing contributions to flavour-changing neutral currents, which can be problematic in SUSY models. After this we demonstrate that if more than one SUSY-breaking sector is present then this could lead to a rich spectrum of states with mass roughly twice the gravitino mass. In particular, if SUSY-breaking in a hidden sector arises dynamically then multiple ‘Goldstini’ and ‘Modulini’ states can arise, which couple to visible sector fields via the ‘Goldstino Portal’. We also demonstrate a new phenomenon which can occur in the context of multiple hidden sectors. If one sector breaks SUSY then this can ‘stimulate’ other sectors into also breaking SUSY, even if they are incapable of doing so on their own. Part II focusses on the matter in our Universe. We review our current understand- ing of how the visible matter in our Universe came into existence, and our current understanding of the nature of dark matter (DM). Following this we describe how DM could potentially be indirectly observed through its effects on cold white dwarf stars. Alternatively, if DM were detected by independent means, then observed cold white dwarfs could be used to place limits on the DM density in globular clusters, giving clues as to how these clusters of stars formed. We then present a new model for the co-generation of both the visible and dark matter in our Universe. This proceeds by generating a particle anti-particle asymmetry in the dark sector, which is then shared with the visible sector. This model predicts the existence of a light, m ≲ 5 eV, scalar particle which derivatively couples to DM, and provides a final state for the symmetric DM component to annihilate away into. Work completed during the period of this D.Phil is contained in [1–8], however only material in [3–6, 8] is presented in this thesis.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:595903 |
| Date | January 2011 |
| Creators | McCullough, Matthew Philip |
| Contributors | March-Russell, John |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:f2a6c703-8b95-4345-9477-4afeea355a8e |
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