Executive Summary : | The study of sub-GeV exotic particles, beyond those in the Standard Model (SM) of particle physics, is at the forefront of research. These particles are invoked in the context of multiple challenges faced by the SM, such as the Dark Matter content of the Universe, portals between the visible and dark sectors, the muon g-2 problem, and the strong CP problem. This project aims to study the theory and phenomenology of exotic bosons with sub-GeV masses, specifically Axion-like particles (ALPs) and dark-photon like light vector bosons (LVBs). To find all possible hints of these particles in various new physics models, researchers need to understand the details of these experiments and determine the types of theoretical models that will lead to these signatures at these experiments. They can then constrain these new physics models from experimental data and use indirect detection techniques, looking at SM flavor data, to give bounds on these new particles (NPs). The presence of these light new particles will modify expectations from the chiral Lagrangian of the Pions, the heavy quark lagrangian of the heavy-light mesons, and the predictions of a vector-meson dominance framework for the light vector mesons. To avoid missing new physics signals and the interplay between different operators that give rise to a particular amplitude, researchers will work in a general Effective Field Theory (EFT) framework, writing down all possible operators at the Electroweak stage based on symmetry considerations. |