Positron

First suggested as a possibility by Dirac, the positron is a positive electron, created as one component of an electron-positron pair when high energy gamma rays interact with matter. The photograph below shows pair production in liquid hydrogen. The paths are visible because of a line of bubbles created by ionization. The paths curl in opposite directions in a vertical magnetic field.

 

The positron was the first example of an antiparticle. The antiparticles of all charged particles have the opposite charge. Uncharged particles also have antiparticles. Gamma rays are produced when a particle combines with its antiparticle. The photon energy is given by Einstein as E = Dmc².

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