Raiders of the Lost ALP

While the Standard Model (SM) of Particle Physics describes with exceptional accuracy a vast amount of natural phenomena, it fails to explain certain experimental observations and theoretical challenges. Thus, extensions of the model are required to address these limitations. This thesis focuses on the exploration of Axion-Like Particles (ALPs) as a suitable extension of the SM. Given the ubiquity of ALPs in several beyond SM models, we employ a model-independent effective field theory framework to investigate the potential interactions between ALPs and the SM particles. Subsequently, the results presented in this thesis can be categorized into two main parts.

On one hand, as the experimental searches for ALPs have become increasingly diverse and precise, they call for the necessity to take into account radiative corrections to the ALP effective theory. In this thesis, the full set of one-loop corrections for the dimension-5 ALP Lagrangian is derived, manifesting their significant impact on experimental ALP searches. Notably, these corrections offer an approach to probe ALP couplings that may be challenging to test directly but induce a sizeable impact on other interactions that are highly constrained by experimental data.

On the other hand, this thesis investigates the phenomenological implications of ALPs in experimental high-energy searches. Specifically, we explore the contributions of ALPs to rare processes within collider searches. For instance, a novel search targeting vector-boson scattering processes is proposed, exploiting the derivative nature of ALPs to probe their electroweak couplings to massive gauge bosons. Moreover, we explore the impact of ALPs on flavor observables, with a particular emphasis on investigating flavor anomalies associated with the B-meson sector. 

While the experimental detection of ALPs remains fruitless at present, the research conducted in this thesis has been productive in systematically exploring the ALP parameter space. Through rigorous analysis, new excluded regions within the parameter space have been identified, providing valuable constraints on potential ALP couplings. Furthermore, these studies have suggested novel promising avenues and valuable strategies to probe these elusive particles in upcoming experiments.