Maximising the new physics reach of the LHC through Effective Field Theories

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Particle physics inspires a sense of wonder, probing the infinitely small in the way that astronomers and space programs explore the infinitely big. Moreover, its collider experiments benefit society, advancing technology in material sciences, electronics and informatics. This global effort to advance our understanding of the fundamental theory of the universe requires a monumental collaboration between theory and experiment, exemplified by the Large Hadron Collider (LHC).We know that the recently discovered Higgs boson at the LHC is not the end of the story; new particles are likely to exist. However, data suggests that they are either too heavy to produce or are light but evade our experiments. Even if they can't be produced directly, we can still infer the presence of new particles through slight modifications of the interactions between known particles. This theoretical framework is called Effective Field Theory (EFT) and is a well established way to test many new physics models at once. The established set of particles and interactions is called the Standard Model of particle physics, and its EFT extension, the SMEFT. However, if new, light particles do exist, they can also be incorporated into a more comprehensive EFT.My proposal conceptually and technologically enhances the global high energy physics programme, providing new predictions for colliders and developing search strategies for new physics through EFTs. I will confront the SMEFT with collider data to search for hints of new physics using SMEFTatNLO, a cutting-edge tool for theoretical predictions that I developed, that has now become the industry standard for calculations of its kind. Using fitmaker, another public software for statistical analysis that I developed, the new calculations will allow me to more accurately determine the impact of collider data on new physics models, and identify pathways to improve our knowledge. These global analyses crystallise our understanding of fundamental interactions and extend the energy reach of colliders. Alongside, I will exploit the tool to perform sensitivity studies of new processes to guide and motivate future experimental measurements and searches. For light, new physics, many possibilities exist. Here, EFTs help to lay out the possible interactions of a given state and provide a framework to discover them through all of their possible interactions. I outline three studies that exploit EFT, motivated by open questions such as the nature of dark matter and the cosmic matter-antimatter asymmetry. The first devises a strategy to disentangle different types of dark matter particle through their LHC production modes. The second determines new probes for light particles coupled to the top quark, which is abundantly produced at the LHC but has not been extensively used to search for these states. Third, I will develop a general model for new physics that can explain the matter anti-matter asymmetry of the universe. Their unique feature is that they avoid the very strong constraints from measurements of the electron electric dipole moment that rule out large classes of these models.The underlying goal of my objectives is to exchange knowledge and expertise with experimental colleagues. I believe that the most important impact that a researcher in theoretical physics can have is to influence and advance the experimental strategy at colliders. It is essential that I communicate my results to the experimental community and support their efforts to search for hints of new physics with my theoretical predictions and sensitivity studies. Throughout, I will ensure that these results and associated tools are transferred experimental colleagues such that they can enhance their own dedicated searches and optimise the data presentation to maximise the impact of their results. Ultimately, my investigations will test the fundamental laws governing the interactions between the elementary constituents of the universe.