Neutrinos are particles that have no electric charge and very little mass. They are one of the most abundant particles in the universe. Neutrinos interact only weakly with matter, which makes them extremely difficult to detect.
Despite their elusive nature, neutrinos are an important tool for astrophysicists and particle physicists alike. Astrophysicists use neutrinos to study some of the most energetic events in the universe, such as supernovae and gamma ray bursts. Particle physicists use neutrinos to probe the inner workings of the Standard Model of particle physics.
The Standard Model is a theory that describes the fundamental particles of matter and their interactions. It is our best current description of how all known matter in the universe behaves. However, it does not include gravity, and it cannot explain certain phenomena like dark energy or dark matter. Neutrino physics is one way scientists are searching for evidence beyond the Standard Model.
Neutrinos come in three types, or “flavors”: electron neutrinos, muon neutrinos, and tau neutrinos. The different flavors arise because neutrinos can change from one type to another as they travel through space. This process is called “neutrino oscillation” .
Oscillation occurs because each flavor of neutrino has a different mass . The heavier flavors (muon and tau) tend to change into lighter ones (electron) as they travel; the lighter flavors (electron) tend to change into heavier ones (muon or tau). This changing back-and-forth between flavors is what gives rise to oscillation . Scientists can detect these flavor changes by looking for anomalies in high-energy cosmic rays .