Antinucleons

Antinucleons are the antiparticles of nucleons. Nucleons are the particles that make up atomic nuclei, namely protons and neutrons. Therefore, an antinucleon is either an antiproton or an antineutron.

Antiprotons have the same mass as protons but carry a negative electric charge instead of a positive one. Antineutrons have the same mass as neutrons but are composed of antiquarks instead of quarks. While neutrons are electrically neutral, antineutrons possess a neutral charge, but their constituent antiquarks mean they have a different magnetic moment compared to neutrons.

When an antinucleon encounters its corresponding nucleon, they annihilate each other, releasing a significant amount of energy, typically in the form of gamma rays or other particle-antiparticle pairs. This annihilation process is governed by the principle of matter-antimatter annihilation.

The existence of antinucleons was predicted by theoretical physicist Paul Dirac in his relativistic theory of the electron, which led to the broader concept of antimatter. The antiproton was experimentally discovered in 1955 by Emilio Segrè and Owen Chamberlain, who were awarded the Nobel Prize in Physics for their work. The antineutron was discovered shortly thereafter in 1956.

Antinucleons are produced in high-energy particle collisions, such as those that occur in particle accelerators or in certain cosmic ray interactions. They are also thought to have been created in the very early universe during the Big Bang. Studying antinucleons is crucial for understanding the fundamental symmetries of nature, such as charge conjugation symmetry, and for probing the structure of matter.