Phenomenological applications in cp-violating systems in the sm and beyond

Abstract

The current knowledge on the structure of matter is the result of a huge experimental and theoretical effort. Our Universe is composed of elementary particles governed by the four fundamental forces: gravitational, weak, electromagnetic and strong forces. The Standard Model (SM) of particle physics is the simplest theoretical description of how these particles and forces, except for the gravitational force, are related to each other. Along the years, the SM has been able to explain all the experimental data with high accuracy, culminating in 2012 with the discovery of the Higgs boson. Its elegance, simplicity and high predictivity have converted the SM in the best theoretical reference framework to date. Despite being a successful description of the reality, there are some phenomena that the SM does not explain such as the large matter-antimatter asymmetry. In the early Universe, the Big Bang should have resulted in the same proportions of matter and antimatter, but nowadays we observe that almost everything around us is made of matter except for a small amount of antimatter. One of the grand challenges facing physics is understanding why we observe this asymmetry. CP violation is one of the necessary ingredients to generate this large asymmetry. In spite of including all needed ingredients, the SM is unable to completely generate the observed asymmetry. Therefore, extensions of the SM with new sources of CP violation could explain the size of this asymmetry. The main objective of this work is precisely the study of phenomenological systems where the CP symmetry is violated. This thesis is divided in seven chapters. In Chapter 1, we present a comprehensive overview of the SM, showing how its interactions emerge from symmetry principles. The last part is dedicated to the flavour sector of the SM where the CP violation phenomena is introduced through the Cabibbo-Kobawashi-Maskawa (CKM) matrix. Finally, we present the different ways in which this phenomena can appear in nature. The concept of Effective Field Theory (EFT) is introduced in Chapter 2, providing a powerful theoretical approach for the physical systems studied along this thesis. The theoretical determination of the direct CP-violating ratio $\varepsilon'/\varepsilon$ in the SM is the first phenomenological application presented in this thesis which can be found in Chapter 3. Using the theoretical framework of Chiral Perturbation Theory ($\chi$PT), we obtain a SM prediction in complete agreement with its experimental measurement. Finally, in Chapter 4 we update the previous prediction including the known isospin-breaking corrections. In Chapter 5, we perform a one-loop computation of the short-distance contributions for the neutral meson mixing in a quite general extension of the SM, the Aligned-Multi-Higgs-Doublet Model (AMHDM). This extension accommodates new sources of CP violation that could reproduce the size of the observed matter-antimatter asymmetry of the Universe. Finally, these sources are strongly constrained from the current flavour data. In Chapter 6, we obtain new limits for the charm and bottom quark electric dipole moments (EDMs) using the renormalization group equations (RGEs) and the strong bounds on their chromo-EDMs.