| The Little Higgs class of models extend the Standard Model of particle physics by embedding the electroweak gauge groups into a larger group structure. These models always contain new gauge bosons with distinctive properties. In this dissertation I study the new gauge bosons of two models in the Little Higgs class, the Littlest Higgs model and the Simplest Higgs model. Recent direct searches for new massive particles place constraints on the free parameters of the Littlest Higgs model. Depending on the choice of model free parameters, the direct search limit on the global symmetry breaking scale can range from as low as a few hundred GeV to in excess of 4.5 TeV. A low-mass neutral gauge boson is shown to be present and yet undetectable in dilepton decays for a significant range of parameter space due to decoupling from Standard Model leptons, providing a counterexample to broad claims that a new neutral gauge boson is ruled out to a high mass scale. For some choices of free parameters, the couplings of gauge bosons to scalars in Little Higgs models can become strong, resulting in a breakdown of perturbative calculation. I study this in the Littlest Higgs model, where the approach to perturbative breakdown is characterized by increasing decay widths of the neutral Z H boson to a lighter gauge boson plus multiple scalars, and so by a distinctive collider signature of large Higgs multiplicities. The gauge boson phenomenology of the Simplest Higgs model is studied in depth, after a review of Lagrangian and development of the particle spectrum and Feynman rules. A Z' vector boson is found to be highly distinctive, and its Standard Model Z0-like angular distribution is displayed. Production and branching ratios for the X and Y gauge bosons are calculated. These bosons will have low yields at the Large Hadron Collider. For most parameter choices the primary Y boson decay branch is to two neutral scalars, Higgs and the eta. |
