**Scattering Processes of Elementary Particles**, an Introduction to Feynman Diagrams and to the Feynman Calculus

20 pages, 9 line figures, 2011

**Feynman diagrams** are handy aids to deal with quantum electrodynamic phenomena involving elementary particles.

To each event one or more diagrams can be assigned which are the starting points for formulating the so-called **invariant matrix element**. This quantity is the main part of the cross section of the mentioned particle process.

The procedure with Feynman diagrams is recipe like and is named **Feynman calculus.**