Wing Sheung Chan

The Standard Model and lepton flavour violation 7 equation into smaller sectors where we list out the field (particle) contents of the model and discuss their properties and interactions in a more accessible and conceptual way. Overview The fields that appear in Equation (1.9) can be interpreted as elementary particles in the SM. These particles interact with each other in ways that are completely determined by the Lagrangian. Figure 1.1 summarises the properties of all the elementary particles and the interactions that they participate in. For each of these particles, there also exists an antiparticle that has the same properties but carries opposite charges. Analogous to the periodic table of chemical elements, these elementary particles can be categorised into several classes according to their properties. And just like how patterns in the periodic table have lead to the discovery of the atomic structure, symmetries in the SM that are now considered to be fundamental might one day also lead to a deeper understanding of Nature. Figure 1.1.: Elementary particles in the Standard Model of particle physics. Matter particles In the SM, all known matters are composed of elementary fermions ( f ). They are the fundamental building blocks of our everyday world and the directly observable universe. Without counting antiparticles and different colour flavours, there are 12 unique elementary