Hints of a Hidden World

Abstract

Despite extensive theoretical and experimental efforts, we have yet to discover evidence of new physics. Since there is no obvious candidate for a particular new physics model that can resolve the variety of anomalies and shortcomings of the Standard Model, a potentially lucrative strategy is to explore as broadly as possible. In this dissertation we consider a two pronged approach to this strategy: constructing phenomenological models that capture the dynamics of general new physics scenarios, and developing robust tools for identifying new phenomena. We consider primarily the application of this strategy at existing and future colliders. For phenomenological models, we first consider the generic scenario where new particles are produced back-to-back with substantial transverse momenta, ultimately decaying into a dimuon pair. We also use extra dimensional models to construct tractable hidden sector scenarios with tunable radiation patterns. For both of these toy models, we expect signal events to look inherently distinct from Standard Model backgrounds. To classify these signatures, we develop a new event shape observable—event isotropy—that has a complementary dynamic range to commonly used event shapes. We discuss the efficacy of this observable and explore potential correlations. Finally we discuss how this program for new physics searches can expand even further with the construction of a multi-TeV muon machine. We show how using muons increases sensitivity to new physics scenarios that couple to second-generation particles and how we can use an O(TeV) beam in a beam-dump experiment to probe enormously small couplings. Ultimately we present many possible channels towards uncovering the first hints of new physics to motivate more concentrated efforts to identify the particle content of the universe.