Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




Marc Sher


Over the years, the Standard Model has proved itself to be an extremely durable theory. In spite of its success, very few empirical clues have emerged about the nature of the electroweak symmetry breaking that lies at its heart. With results from the LHC around the corner, this will hopefully change soon. In this dissertation we examine several possibilities for electroweak symmetry breaking and discuss various extensions to the Standard Model to resolve known problems. We begin by providing a brief overview of electroweak symmetry breaking, two Higgs doublet models, and supersymmetry. We then present a supersymmetric model that allows for small, Dirac neutrino masses. We find that it yields dramatic multi-lepton signatures, which have extremely small backgrounds. Next we discuss the leptophilic two Higgs doublet model and construct its supersymmetric analogue. Bounds on this model as well as its phenomenology are presented. We then show that an extension of this model includes a dark matter candidate that is capable of explaining a possibly observed excess of gamma-rays coming from the Galactic Center.



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