Particle Physics
High energy physics phenomenology largely revolves around the ability to make precise mathematical predictions for high energy experimental measurements. For collision-based experiments, these predictions typically stem from cross-section and decay-rate computations. Roughly speaking, the cross section and decay rate of a process tells us how probable or likely an interaction is between two ‘states’ - characterized by their properties before- and after- the collision/decay (cross-sections are typically associated with multi-particle initial and final states where as decay-rates are associated with single- to multi- particle initial and final states). These quantities are measured and reported explicitly by experiments and most importantly, can be computed theoretically using the mathematical tools of quantum field theory.