Indeed, that's the classic example given for a Feynman diagram and it shows the presence of a positron and its movement along -t. https://en.wikipedia.org/wiki

Indeed, that's the classic example given for a Feynman diagram and it shows the presence of a positron and its movement along -t. https://en.wikipedia.org/wiki/Feynman_diagram https://en.wikipedia.org/wiki/Feynman_diagram