Positron

The positron is an antiparticle of the electron predicted in 1928 by Paul Dirac. It was discovered in 1932 in cosmic radiation by Carl David Anderson.

Carl Anderson performing an experiment. (Credits: Universe-review).

Positrons are, for example, produced by beta+ radioactivity and during the creation of electron/positron pairs by a gamma ray passing close to a nucleus (this is important for the conservation of momentum). Today they are used in medical imagery in Pet-Scans.