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Abstract

This thesis aims to study a novel solution to the Strong CP Problem. As no experimental signals of an axion have been found yet, the Nelson-Barr mechanism is gaining more and more popularity. After a review of the Standard Model and the Strong CP Problem, a model is introduced which combines the Nelson-Barr mechanism with a non-conventional CP transformation of order 4. A slightly improved calculation of the 2-loop contribution to θ is presented and the decoupling limits of the model are discussed. While the abso- lute scales of the model evade prediction, a combination of the energy scales and Yukawa couplings is found that can be constrained. Fitting the model via Markov Chain Monte Carlo algorithm to experimental results supports these findings. For the fit, a focus on CP violating observables in the quark and meson sector is chosen. While the solution to the Strong CP problem might lie at energies far above the experimentally accessible scales, our results show a novel way to still constrain at least specific combinations of these high- energy scales. In the future, these results can work as a starting point to help constrain new creative model building ideas.