Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




Marc Sher


The Standard Model of particles and fields has been around for about 30 years, and has been remarkably successful. However, it is widely believed to be incomplete, and theorists have studied various extensions to the model. These extensions can take many forms. An example of this is the framework Colladay and Kostelecky have proposed for studying Lorentz and CPT violation in a natural extension of the Standard Model. We determined the first bounds on the parameters in the Higgs sector. The bounds on the CPT---even asymmetric coefficients arise from the one-loop contributions to the photon propagator, those from the CPT---even symmetric coefficients arise from the equivalent cmunu coefficients in the fermion sector, and those from the CPT odd coefficient arise from bounds on the vacuum expectation value of the Z-boson. It is also interesting to look at the gauge structure of the Standard Model, and determine new effects that may arise if it is altered. One way to do this is to extend the SU(3)c x SU(2) L x U(1)Y gauge group to SU(3)c x SU(3)L x U(1) X, or what is called a 331 model. We studied variants of these models which are characterized by each lepton generation having a different representation under the gauge group. Flavor-changing neutral currents in the lepton sector occur in these models. to satisfy constraints on mu → 3e decays, the Z' must be heavier than 2 to 40 TeV, depending on the model and assignments of the leptons. These models can result in very unusual Higgs decay modes. In most cases the mutau decay state is large (in one case, it is the dominant mode), and in one case, the phi → ss?» rate dominates. Finally, it is possible to combine these approaches. This is particularly tempting in the currently exciting field of neutrino phenomena, where a combination of the 331 model with CPT-violating terms provides the terms necessary to explain the LSND anomaly, as well as the atmospheric and solar neutrino data. We also find predictions for relationships between the neutrino masses.



© The Author

Included in

Physics Commons