Positron
A positron is the antiparticle of the electron. It is antimatter, has an electric charge of +1, a spin of 1/2, and the same mass as an electron. When a positron annihilates with an electron, their mass is converted into energy in the form of two gamma ray photons, see Electron-positron annihilation.
A positron may be generated by positron emission radioactive decay, or the interaction of photons of energy greater than 1.022 MeV with matter. This process is called pair production, as it generates both an electron and a positron from the energy of the photon.
The existence of positron was first postulated in 1928 by Paul Dirac. In 1932, positron was observed by Carl D. Anderson, who gave positron its name. Interestingly, Anderson also suggested, unsuccessfully, to rename electrons to "negatron."
See also
