positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 e, a spin of 1/2, and about the same mass as an electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more photons. Positrons can be created by positron emission radioactive decay, or by pair production from a sufficiently energetic photon which is interacting with an atom in a material.
