PROPERTIES OF ANTIMATTER

Atoms are defined as being made of electrons, which orbit around protons and neutrons that make up their intrinsic nuclei. According to the standard model, every particle has a corresponding antiparticle. These particles all interact with each other by means of other particles, such as photons and gluons. Based on the attributes that these particles possess, we can assign them identifying components, called quantum numbers, and by way of symmetries and conservation laws involving quantum numbers, their interactions are able to be described. Charge and intrinsic angular momentum, or spin, are examples of such quantum numbers. If a particle possesses no attributes other than linear and angular momentum, then it is its own anti-particle. However, if a particle has other attributes, such as an electric charge (Q), then the anti-particle will have the opposite attributes, or a charge of (-Q). In general, particles and anti-particles have the exact same mass and equal, but opposite charges and magnetic movements (an electromagnetic property that determines the force that acts on a particle as it moves through a magnetic field).

Positron

A positron is the antiparticle counterpart of the fundamental particle electron. A positron has the same mass as that of an electron, and the same spin. Both particles also have the same amount of electric charge, but whereas the electron's is negative, the positron's is positive.

Antiproton

An antiproton is the antiparticle counterpart of the proton. Since protons/antiprotons are not fundamental particles, they are composed of smaller particles called quarks. Additionally, because a proton consists of two up quarks and one down quark, an antiproton similarly consists of two anti-up quarks and one anti-down quark. Although a proton has an electric charge of +1 and a positive magnetic moment, its antiparticle, the antiproton, which is identical in almost every other respects, has an electric charge of -1 and negative magnetic moment.

Antineutron

The antineutron is the antiparticle counterpart of the neutron. An antineutron has the same mass as a neutron. However, it is different from a neutron by being composed of antiquarks, rather than quarks. In particular, whereas the neutron consists of one up quark and two down quarks, the antineutron consists of one anti-up quark and two anti-down quarks. Both the neutron and its antiparticle, the antineutron, have no electric charge, but their magnetic moments are opposite.

Annihilation

Annihilation occurs when a subatomic particle collides with its respective antiparticle. Since energy and momentum is conserved, the colliding particles either release energy and/or form new particles. Furthermore, particles have opposite quantum numbers from their antiparticles, so that the sums of all quantum numbers of the original pair are zero. During low-energy annihilation, photon (usually a gamma ray) production is preferential because these particles have no rest mass. Conversely, high-energy particle collisions produce annihilations where wide assortments of heavy particles are created since there is enough kinetic energy in their relative velocities to provide the rest energies of those particles of which they create. It is still possible to produce photons and other light particles, but they will emerge with higher energies. One example of annihilation is when a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two gamma ray photons: