Expecting the unexpected: Signals for new physics

In the near future our theories of Beyond the Standard Model physics will be confronted with a wealth of new data. The impending turn-on of the LHC and the continued proliferation of cosmology and dark matter experiments are ushering in a new era for high energy physics. It will be crucial for theorists to be ready to anticipate the full breadth of experimental signatures that new physics could bring. In this thesis, we discuss a diverse set of examples of such signatures.;First we examine the effects of the extended gauge sector of the Littlest Higgs model in high energy e+e - collisions. We find that a study of the processes e+e- → f f¯ and e+e - → Zh at s = 500 GeV International Linear Collider can cover essentially the entire parameter region of this model. This allows for confirmation of the structure of the cancellation of the Higgs mass quadratic divergence and would verify the little Higgs mechanism.;We then consider the large extra dimensions scenario, examining the production and evolution of microscopic black holes in the early universe. We demonstrate that, unlike in the standard four-dimensional cosmology, in large extra dimensions absorption of matter from the primordial plasma by the black holes is significant and can lead to rapid growth of the black hole mass density. This effect can be used to constrain the conditions present in the very early universe. We demonstrate that this constraint is applicable in regions of parameter space not excluded by existing bounds.;The third signature we study is W pair production in the Noncommutative Standard Model constructed with the Seiberg-Witten map. We consider partial wave unitarity in the reactions W+ W- → W+ W- and e+ e- → W+ W-, and show that tree-level unitarity is violated when scattering energies and the noncommutative scale are around a TeV. We find that while WW production at the LHC is not sensitive to scales above the unitarity bounds, noncommutative scales below 300--400 GeV are excluded by LEP-II, and the ILC is sensitive to scales up to 10--20 TeV. In addition, we find that the ability to measure the helicity states of the final state W bosons at the ILC provides a diagnostic tool to determine and disentangle the different possible noncommutative contributions.;We then turn our attention to the recently proposed unparticle scenario. We explore how modifications to the unparticle propagator from conformal symmetry breaking and vacuum polarization corrections affect the calculation of the lepton anomalous magnetic moment. Our numerical study shows that allowing various SM fermions to run in the unparticle self-energy loops does not significantly affect the value of g - 2. We also investigate the limits on a characteristic mass scale for the unparticle sector in the case that the conformal symmetry is broken.;Finally, we study LHC signatures of the Minimal Supersymmetric Standard Model. We perform a scan of MSSM parameter space, and apply all relevant experimental constraints to obtain a general set of viable MSSM models. We pass our models through a detailed LHC analysis and discover a large number of novel SUSY signatures. By studying these new signatures, we help elucidate the true breadth of the MSSM.