It was in the year 1829, after several contributions to the development of Quantum Mechanics, that Paul Dirac discovered that there was a particle similar to the electron, whose symbol is (and-), but this particle had a different charge, that is, it was a positively charged particle. Through studies carried out by scientist Carl Anderson (1932) on cosmic radiation, the positron, whose symbol is (and+).
By the various studies related to the new particle discovered at the time, several physicists, a little later, recognized the existence of an antiparticle for every existing particle. So they came to the conclusion that the members of these pairs have the same spin, the same mass, opposite electrical charges, and opposite-sign quantum numbers.
The name particles was used initially to designate the most common particles, the same ones we know today, for example, protons and neutrons. The name antiparticle was used for rarer particles. Today we know that the names particle and antiparticle came to be used based on certain conservation laws. Today the terms antiparticle and particle are used to refer to particles.
In several texts and articles, although it does not always happen this way, physicists represent an antiparticle by employing a slash over the symbol of the particle it mentions. In this way, we can, for example, express the proton symbol and the antiproton symbol as follows: P is the proton symbol, P? (read p bar) is the symbol for the antiproton.
If we were to make two particles, a particle and its antiparticle, collide, we would see that they would disappear, causing the energy they had before the collision to assume new forms. If we had mutual annihilation of an electron and a positron, we would see that two gamma rays are produced:
If the electron and positron are stationary at the moment of annihilation, the total energy is equal to the sum of the resting energies of the two particles and is shared equally by the two photons. Since the total linear momentum must be conserved, the photons are emitted in opposite directions.
By Domitiano Marques
Graduated in Physics
Brazil School Team
Source: Brazil School - https://brasilescola.uol.com.br/fisica/particula-antiparticula.htm
