Effective field theory flavored paths to beyond the standard model dynamics

Resumen

The aim of this thesis is to partially address some of the current physical unknowns by studying the effects of new physics on the predictions of the Standard Model for several observables. The thesis is organized in 3 parts. In Part I we introduce the two frameworks that serve as the building blocks of the material presented in the rest of the text. Part II and III are then devoted to present the core of the work done during the PhD. Each of the aforementioned parts contains 2 chapters. Hence, the thesis consists of a total of 6 chapters, a summary and a list of appendices that complement some of the calculations presented in the main text. In Chapter 1 the Standard Model of particle physics is reviewed. The basic QFT description of its particle content is given, followed by a detailed description of the strong and electroweak sectors. The spontaneous symmetry breaking mechanism is recalled at the end of the chapter. Chapter 2 focuses on the framework of effective field theories. First, their theoretical underpinnings are explained. Then, Chiral Perturbation Theory, the dual theory of QCD at low energies, is presented together with its extension Resonance Chiral Theory. This is followed by the description of the effective field theory of the Standard Model and its low-energy realization. Part II collects two strongly related works. Chapter 3 is dedicated to our phenomenological analysis on charged-lepton-flavor violation on tau leptons. After a historical and theoretical introduction of flavor is given, the techniques to compute the observables of interest are presented and the statistical tool used in the analysis is introduced. The corresponding results are given in several sections. These results are later used in Chapter 4 to set bounds on a general leptoquark framework. Such a framework is presented and the relevant interactions contributing to the observables studied in Chapter 3 are highlighted. Then the results are presented for scalar and vector leptoquars separately. Part III contains two unrelated chapters that deal with neutrino physics. In Chapter 5 the full effective field theory description of the COHERENT experiment with its coherent elastic neutrino-nucleus scattering detection process is provided. The oscillatory behaviour of the neutrinos involved in the experiment is characterized within the QFT formalism. Finally, some preliminary results are shown. The last Chapter 6 deals with a particular extension of the Standard Model addressing the generation of neutrino masses: the linear seesaw model. Within this model, the Quasi-Dirac nature of the extra heavy neutrinos is studied. The chapter ends with a phenomenological analysis that helps to constrain the parameters of the model. We close with a comprehensive summary of the thesis in Catalan and several appendices.