Feynman diagram symbols
We use this code on the diagrams, you might find different codes used by some publishers. This one code is used by the Institute of Physics and is common, but not universal.
The particles entering and leaving the interaction (fermions) are shown as solid lines. Exchange particles shown here are either photons or a weak interaction bosons.
The changes in direction of the particles simply represents a change in momentum. They are not vector diagrams, there is no scale. An upward arrow on the line shows a real particle and a downward arrow is an antiparticle.
For example, interaction between two electrons.
The wavy line represents the energy change
or exchange particle which has a
brief or virtual existence.
In this case a photon
PDF and video lesson
You can download a PDF of these notes here:Feynman diagram notes
There is a short video lesson below which explains a little more thoroughly.