Types of Neutrinos
Neutrinos are of 3 types or flavors: the electron-neutrino, the muon-neutrino and the tau-neutrino. The electron-neutrino is released during beta decay – a process where an electron is emitted from an atom which decays into a lighter element. The Tau and Muon particles are heavy versions of the electron. They are unstable, so they decay. Muon-neutrinos and tau-neutrinos are released during the decay of the Muon and Tau respectively.
A bizarre feature of the neutrino is that it can change its flavor or “oscillate” from one flavor to another. This means that an electron neutrino can convert into a muon neutrino and then back into electron neutrino depending on the distance travelled. This property of neutrinos was postulated when experiments involving neutrinos did not observe the expected number of neutrinos. Few initial experiments were the solar neutrino experiment (neutrinos from the sun) and the atmospheric neutrino experiment (neutrinos from cosmic rays hitting the atmosphere). The observed neutrinos were less than the expected number in both of the mentioned experiments. Why was there a difference n the number of detected neutrinos? Because scientists were trying to detect one type of neutrino. But, that neutrino had oscillated into another neutrino, therefore, they were detecting less neutrinos.
How does it happen?
Each type of neutrino has some mass. But for some mysterious reason, some specific type of neutrino does not have the “specific mass” it should have. For example, intuitively, the electron-neutrino should have some specific mass M1, the muon-neutrino should have some specific mass M2 and the tau-neutrino should have a specific mass M3. But, this is not the case. Each variant of the neutrino has a different combination or superposition of the masses M1, M2 and M3. This combination constantly keeps on changing when a neutrino moves through space.
Let’s call the combination of the 3 masses for the electron neutrino as C1 and the combination of masses for the muon neutrino to be C2. As the mas combination keeps on changing, after some time the mass combination C1 changes or “oscillates” to C2. Therefore, the electron-neutrino “oscillates” into a muon-neutrino. Again after sometime, the mass combination C2 “oscillates” back to C1. Therefore, the muon-neutrino converts or “oscillates” back into the electron Neutrino. This process repeats again and again, meaning it keeps oscillating.