An introduction to particle physics.
One of the beta decay processes is the emission of positrons to reduce the nuclear positive charge. The positron is actually an antiparticle of electron, but we did not mention the antiparticle concept at that time.
Paul Dirac rearranged Einstein's equation of relative mass for a moving particle in 1928, and obtained an equation showing that the kinetic energy of certain type of particles became more negative as they move faster. He called such particles antiparticles.
Antiparticles and their counter parts have the same rest mass, but opposite charge opposite spin, and opposite magnetic moment if they possess these properties.
While studying cosmic-ray tracks in his cloud chamber in 1932, Carl Anderson saw tracks similar to those of electrons but these particles bent in opposite direction in the presence of a magnetic field. He discovered antielectrons prescribed by Dirac, and called them positron.
At the end of the positron tracts, Anderson noticed two thin tracts that can be attributed to gamma rays, generated when the positrons were annihilated when colliding with electrons.
A year later, the creation of an electron-positron pair using high-energy photon was confirmed, and this process is called pair production.
Today, positrons and electrons are created routinely using high-energy photons. These particles are created for particle accelerator. Electrons and positrons move in opposite directions in circular accelerators accelerated using electric and magnetic fields. When high-energy electrons and positrons collide, particles with rest mass heavier than electrons are produced.
Simhony argued that electrons and positrons form a elecron-positron lattice, (EPOLA), which is unobservable. Absorption of 1.02 MeV liberates a pair of electron and positron. Thus, energy does not convert to particles. It is absorbed, and as a result, particles are liberated.