Radiative Corrections: Introduction

Now that we have acquired some experience at performing QED calculations, let us move on to some more complicated problems. Chapter 5 dealt only with tree-level processes, that is, with diagrams that contain no loops. But all such processes receive higher-order contributions, known as radiative corrections, from diagrams that do contain loops. Another source of radiative corrections in QED is bremsstrahlung, the emission of extra final-state photons during a reaction. In this chapter we will investigate both types of radiative corrections, and find that it is inconsistent to include one without also including the other.