In quantum physics, the positron was discovered in 1932 as the antimatter counterpart of the electron.
Paul Dirac’s relativistic equation for the electron, published in 1928, allowed solutions that led to the prediction of an electron-like particle with positive charge. Carl Anderson observed tracks consistent with this particle in cosmic-ray photographs taken in a cloud chamber in 1932. The discovery provided the first direct evidence for antimatter.
A positron has the same mass and spin as an electron but carries electric charge +e instead of −e. When a positron meets an electron, they can annihilate, commonly producing two gamma-ray photons when the pair is initially at rest. The reverse process, pair production, can create an electron and positron from sufficiently energetic radiation near a nucleus or another interaction partner.
The positron is not the same as a proton. A proton is a composite matter particle made of quarks, whereas a positron is an elementary lepton and the electron’s antiparticle.