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Doctor of Philosophy (Ph.D.)




The main topic of this dissertation concerns alternative models of CP violation and the rates predicted by these models for the particular decay {dollar}K\sb{lcub}L{rcub}\to\pi\sp0\nu\bar\nu .{dollar} This decay is promising as a probe of the origin of CP violation in the kaon system. It is virtually free of hadronic uncertainties and its branching ratio would (along with a measurement of the CP asymmetry in {dollar}B\sbsp{lcub}d{rcub}{lcub}0{rcub}\to\psi K\sb{lcub}S{rcub}){dollar} allow a determination of all the elements of the CKM matrix (assuming all CP violation arises from the CKM matrix).;The first group of models of CP violation considered consists of three extensions of the Higgs sector. The simplest extension (formed by adding a second Higgs doublet), the Liu-Wolfenstein model (a model of spontaneous CP violation), and the Weinberg model (a three-doublet model). In a model with an extra doublet, with CP violation arising from the CKM sector, the rate can increase by almost 75%. However, for models in which the CP violation arises either entirely or predominantly from the Higgs sector, it is found that the decay rate is much smaller than that of the standard model, unless parameters of the model are fine-tuned. There are also models where {dollar}K\sb{lcub}L{rcub}\to\pi\sp0\nu\bar\nu{dollar} can have a rate as large as that of {dollar}K\sp{lcub}+{rcub}\to\pi\sp{lcub}+{rcub}\nu\bar\nu .{dollar}.;The second group of models considered consists of manifest and pseudo-manifest left-right symmetric models. These models have a 2 x 2-matrix Higgs structure and introduce nontrivial phases through complex vacuum expectation values. as in the case of extended Higgs models, a significant decay rate is found only for the CKM sector and not for the Higgs sector.



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