Precision physics at High Luminosity LHC and future colliders

Abstract

The Standard Model (SM) of particle physics is the currently established theoretical framework which describes, at a fundamental level, interactions among elementary particles. The construction of high-energy colliders such as the Large Hadron Collider (LHC) at CERN, the largest particle accelerator ever built, allowed scientists to test their models at increasingly high energy scales. In recent years, the LHC has increasingly focused its attention on the precise measurements of SM processes, as they play a crucial role in the exploration of new physics. The emphasis on precision physics has also motivated the development of the high luminosity (HL) LHC upgrade, and the proposal of new high precision machines such as the FCC-ee. In this context, the theoretical effort has to match the experimental work, because precise measurements require an equal precision of the SM predictions. This argument applies also to theories Beyond the Standard Model (BSM), and it becomes particularly relevant in the case of Effective Field Theories (EFTs), where higher-order corrections can significantly impact the bounds on new physics. The main focus of this thesis is the precision calculation of processes in the SM and Standard Model Effective Field Theory (SMEFT) framework, including gg → HH, Drell Yan production qq → ll, and electroweak observables. Finally, the ultimate goal is to make accurate predictions that can be tested on future colliders, such as HL LHC and Fcc-ee. The study of this area is very important, and it gives crucial information on the structure of new physics beyond the SM.