The NOvA (NuMI Off-axis νe Appearance) experiment in Minnesota in the U.S. is shedding light on one of nature’s most elusive particles: neutrinos.
The experiment was designed to determine the role of neutrinos in the evolution of the cosmos. It does this by trying to understand which neutrino type has the most mass and which type the least.
This is an important detail because neutrinos may get their mass through a different mechanism from other matter particles. Unravelling it could answer many open questions in physics.
Physicists study how neutrinos change their type as they travel large distances. This quantum mechanical phenomenon is called neutrino oscillation.
For example, all neutrinos from the Sun are electron-neutrinos, yet we receive a big chunk of them on the earth as muon-neutrinos.
Theoretical models predict two possible solutions for the neutrino mass hierarchy problem, called normal and inverted. The normal order proposes that one of the three types is much heavier and that the other two have comparable lower masses. In the inverted order, one of the neutrino types is lighter and the other two have comparable heavier masses.
A new NOvA data favours the normal order, but not conclusively.
Neutrinos
Neutrinos are a type of subatomic particle. They don’t have an electric charge, have a small mass, and are left-handed which means that the direction of its spin is opposite to the direction of its motion.
Neutrinos are the second-most abundant particles after photons (particles of light) and the most abundant among particles that make up matter.
These particles are produced when particles called leptons interact with matter. For example, when a type of lepton called a muon interacts with matter, the interaction produces a muon-neutrino. The same goes for electrons (electron-neutrino) and tauons (tau-neutrino).
However, the neutrinos themselves interact with matter very, very rarely to produce a corresponding muon, electron or tauon. This small interaction rate makes studying neutrinos difficult.
(Source: The Hindu)
