selfantiparticles

Selfantiparticles are a hypothetical type of elementary particle that is its own antiparticle. This means that the particle and its antiparticle are identical in terms of mass and charge, but would differ in some other quantum property, if such a distinction could even be made. The most well-known candidates for selfantiparticles are the neutrino and the photon.

Neutrinos are electrically neutral and have extremely small masses. If a neutrino were its own antiparticle, it would be a Majorana fermion. This property would have significant implications for the mechanism of neutrino mass generation, potentially involving a process called neutrinoless double beta decay. The observation of this decay would be strong evidence for neutrinos being Majorana particles.

Photons, the quanta of the electromagnetic field, are also electrically neutral and massless. They are currently understood to be their own antiparticles based on standard quantum field theory. A photon is its own antiparticle because its antiparticle, the antiphoton, would have the same properties. However, the concept is less debated for photons than for neutrinos due to the established nature of electromagnetism.

The theoretical exploration of selfantiparticles is an active area in particle physics, as confirming their existence or properties could shed light on fundamental questions about the universe, such as the matter-antimatter asymmetry.