Teorías efectivas aplicadas a la física más allá del Modelo Estándar

Resumo

The Standard Model is the theory that comprises our current understanding of fundamental interactions, but we have several reasons, both theoretical and experimental, to believe that it cannot be the end of the story and there must be new physics beyond it. However, despite decades of search over a long range of energies, we still do not have clear signatures of new physics. This motivates the use of Effective Field Theories as an efficient way of performing the search, because it allows to split the problem in two steps: an agnostic parametrization of the possible deviations of the Standard Model and the connection between these deviations and models of new physics. This translation can be done at various levels in a perturbative expansion, and both the increasing precision in experiments and the necessity of capturing some otherwise missing effects require performing it at one loop. Being a model-dependent process makes it cumbersome and prone to errors to do it for the large number of possible models that we could be interested in. The automatization of this task would be therefore very useful to simplify the connection between theories and experimental consequences and it is a problem we address in this thesis. Besides its efficiency, Effective Field Theories provide us the mechanism to order the mentioned deviations by their size, so that only a number of them are observable at a finite experimental precision. This allows us to classify bidirectionally all possible models of new physics and all the effects they generate, thus constructing an Infrared/Ultraviolet dictionary. In this thesis we partially compute this dictionary at one loop for the case of the Standard Model. Finally, we apply the tools previously developed to perform a phenomenologically relevant analysis, in particular concerning the observed tension in the magnetic moment of the muon. We propose a new class of models to account for this tension and a specific example of a model addressing other anomalies as well.