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Clues in the Quest for the Invisible Universe

  • Author(s): Mardon, Jeremy
  • Advisor(s): Nomura, Yasunori
  • et al.

The particle nature of dark matter is one of the most longstanding mysteries of particle physics. In this dissertation I study several potential clues, both experimental and theoretical, in the quest to understand this invisible component of the universe. In the last few years, data collected by the PAMELA, ATIC, FERMI and H.E.S.S. experiments has revealed several unexpected features in the fluxes of electron and positron cosmic rays. I investigate an interpretation of these anomalies in terms of dark matter annihilating in our galaxy through a ``cascade'' into electrons or muons. I find good ability to reproduce the data whilst evading other experimental constraints. Inspired by these anomalies, I also investigate a simple framework for dark matter, with many similarities to QCD and well motivated in the context of dynamical solutions to the hierarchy problem. In this framework dark matter decays to standard model particles through a cascade, and I again find that it can provide an excellent fit to cosmic-ray data whilst evading other constraints. I consider the implications at the LHC and in future gamma-ray measurements.

More generally, astrophysical and cosmological considerations have a strong interplay with models of physics Beyond the Standard Model and their implications for collider experiments. I investigate the cosmology of the ``Goldstini'' framework in this context. I find that the tensions seen in standard gravitino cosmology are relaxed, and that either gravitinos or goldstinos may be dark matter. I also find that such cosmologically preferred theories may also have the most striking signatures at colliders. The LHC has the potential to observe a ``smoking gun'' signal, in which the Goldstini framework is unambiguously confirmed.

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