1 Theory of Fundamental Interactions

Nothing in life is to be feared. It is only to be understood.

– Marie Skłodowska Curie

Scientific theories are frameworks describing natural phenomena that are capable of making experimentally testable predictions. Oftentimes, they are specified using mathematical language and built on previous observational knowledge and basic properties of the system under study. At the most fundamental scales known to date, the Standard Model (SM) of particle physics is a scientific theory that provides a very accurate description of most of the observed properties and dynamics of the universe around us. It is constructed upon an innovative theoretical framework, generally referred as quantum field theory (QFT), and principles regarding fundamental symmetries of the laws of nature. In this chapter, a non-exhaustive introduction to this theory and its descriptive reach will be provided together with a summary of the known limitations and possible extensions or alternatives. Given the experimental character of the research discussed in the following chapters, the aim of this chapter is not solely the discussion of the basic structure and properties of the theory, but also the methodology followed to compute predictions for observables that can be contrasted with empirical data.