Neutrino, the particle that travels faster than light [Part 2]

Of all the particles physics has dealt with, Neutrinos are surely the strangest. Being able to pass through matter almost without interacting with it makes them so hard to be found. The fact that we hadn't been able to detect them for a long time, if compared to other subatomic particles, doesn't indeed means that they are not very common in our universe.

While you are reading this post, you are being showered by those invisible particles. This happens because they are being produced right now in the sun, as well as in any other living star. Anyway those ones are relatively newcomers, because most of them are relics of older events, such as the Big Bang. One the other hand they are also produced right now on earth, because of radioactivity, as we'll see later.

Those elementary particles are fermions. This means that their spin is one half, and that they obey to Pauli exclusion principle. Recent experiment proved that they have a small, but different from zero, mass and also no charge. This mean that they are not affected by electromagnetic force, but only by weak subatomic force. This explains why they are created in stars and by radioactive decay.

During those kind of reactions three flavors are created: electron, muon and tau neutrinos, and their corresponding anti-neutrino.

Electron neutrinos are created when protons decay in neutrons, producing also a positron.

Muon neutrinos are produced by decay of muons in in an electron and an electron anti-neutrino.

Tau neutrinos are produced by decay of a tau particle in an electron and an electron anti-neutrino.

Neutrinos has we have seen before are created in a precise flavor, but they don't remain in the same one forever. This idea was proposed by Bruno Pontecorvo in 1957, when he predicted that neutrinos are able to oscillate between the three states while travelling through space.

Anyhow the main importance of those particles is related to the development of observation technique, like the one used to the search for solar neutrinos, whose story will be the main topic of the following article.