Antiparticles, or antimatter, are particles’ mirror-world counterparts. These antimatter particles have the same mass as matter particles, but they are diametrically opposed in every sense. The symmetry is beautiful because all of the quantum attributes (such as spin and charge) are reversed. Antiprotons and antineutrons would combine with positrons (the antimatter version of an electron) to generate antiatoms and even antimolecules in an antimatter universe similar to ours. We don’t see much antimatter these days since it annihilates matter in a violent flash of energy when it interacts with it.
Scientists believe that matter and antimatter were produced in equal numbers when the universe originated, and that they should have destroyed. However, as you may have seen, the world around us is not a pure ball of energy. Rather, stuff—matter-based stuff—exists. This is why one of the most common issues posed by physicists is whether neutrinos and their antimatter counterparts, antineutrinos, are the same thing (only differing in helicity). If neutrinos and antineutrinos don’t behave like ordinary matter and antimatter, they could be able to explain how all of this matter managed to survive and evolve into the universe we observe today.
It may seem odd that neutrinos and antineutrinos are the same thing. After all, how can something’s polar opposite be the same as the original? It’s partly due to the fact that certain properties of neutral neutrinos cannot be reversed. Because the electron has a negative charge (-1), the positron, which is its antimatter counterpart, has a positive charge (+1). Neutrinos, on the other hand, have no charge, and the opposite charge of zero is also zero.
Another question to consider is whether neutrinos are Majorana or Dirac particles.
Dirac particles are particles that differ from their antiparticles and are named after Paul Dirac, who originally predicted antimatter particles in 1928 using his equation. (Carl Anderson discovered antimatter in 1932.)
Particles that may operate as their own antiparticle, on the other hand, are known as “Majorana particles,” after Ettore Majorana. In 1937, he suggested the hypothesis that mass neutrinos may transform into their antiparticles and return. Scientists have seen Majorana particles before, so this isn’t completely weird. The photon, a light particle, is an example of a particle that is its own antiparticle. The neutral pion, which is made up of quark-antiquark pairs, and the gluon, which binds quarks together, are two more examples.
The electric charge of a particle and its antiparticle are equal and opposite, as are the values of any other charge-like qualities that the particle possesses. A proton and antiproton, for example, have the same and opposing electric charge, as well as the same and opposite “baryon number.” Even an electrically neutral particle like a neutron has a baryon number that distinguishes it from its antiparticle. The baryon number of the neutron is 1, while that of the antineutron is -1.
Because electrons, muons, taus, and neutrinos are leptons rather than baryons, they do not have a baryon number. However, there is a property called lepton number that is similar. In nature, there may be a preserved lepton number that distinguishes electrically neutral leptons—neutrinos—from their antiparticles, similar to how baryon number distinguishes neutrons from antineutrons. The lepton number of each neutrino is 1, while the antineutrino has a lepton number of -1. Scientists would refer to neutrinos as Dirac neutrinos if they are indeed distinct from antineutrinos, with the difference being the value of the lepton number.
However, it’s possible that the number of leptons in nature isn’t conserved. Nothing distinguishes a neutrino from its antineutrino in that case—not electric charge, not lepton number, and nothing else. A Majorana neutrino is a neutrino that is identical to its antineutrino, according to scientists.
Scientists are attempting to answer this mystery by carrying out difficult experiments that necessitate extremely cold and clean settings. The goal of this study is to find a highly rare predicted phenomenon known as neutrinoless double beta decay, which can only happen if neutrinos are Majorana particles.