Neutrinos fill the whole universe, with about 10 million of them per cubic foot, and most of them zip straight through Earth, and through particle detectors, without leaving a trace. Because they almost never interact with matter, only massive and sophisticated experiments can catch and measure the properties of neutrinos.
The subatomic particles called neutrinos are among the most elusive in the particle kingdom. Scientists have built detectors underground, underwater, and at the South Pole to measure these ghostly particles that come from the sun, from supernovae and from many other celestial objects.
In addition to measuring neutrinos from the sky, physicists on Earth use powerful accelerators to produce neutrino beams containing billions of neutrinos, of which a tiny fraction can be measured by detectors placed in the beam line. At Fermilab, the DONUT accelerator-based neutrino experiment led in 2000 to the discovery of the tau neutrino, the third of the three known types of neutrinos.
Why Neutrinos are Important
Particle Physics has made great progress in the last half century probing the quark half of the fundamental particles. We are now in a position to propose doing similar for the neutrinos. The mixing between the 3 neutrino generations is starting to look very different to its quark counterpart. We don’t know why but it is probably important. Neutrinos may hold the key to understanding why the fundamental particles exist in 3 generations.
Neutrinos are the real oddities of the fundamental particles (only interact weakly, ultra small, but non-zero masses). Science often advances when studying the oddities, such as understanding life processes in general by studying life around deep sea vents.
Neutrinos may only interact weakly, but they are the most abundant particle in the universe with a pivotal role in the evolution of our universe.
A difference between how the neutrino types mix and how the antineutrino types mix is postulated to be the reason why matter dominates over anti-matter in our universe (i.e. why we exist).
PIP-II and Producing Neutrino Beams
The PIP-II project will enable a large increase in the power of Fermilab’s proton beams. This, in turn will produce more powerful neutrino beams. See the animation below to see how this happens.