Neutrinoja

Neutrinoja (neutrinos) are neutral, extremely light elementary particles that interact only via the weak nuclear force and gravity. They come in three flavors—electron, muon, and tau neutrinos—and can oscillate between flavors as they propagate, a phenomenon that implies nonzero masses and a mixing between flavor and mass eigenstates described by the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix.

Neutrinos are produced in a wide range of processes, including nuclear fusion in stars (solar neutrinos), radioactive decay on Earth, nuclear reactors and particle accelerators, supernovae, and interactions of cosmic rays in the atmosphere. They travel at speeds very close to that of light and pass through most matter with only rare interactions, making them challenging to detect yet valuable messengers from otherwise hidden environments.

Mass and nature: The absolute mass scale of neutrinos is not yet known. Oscillation experiments have measured differences between the squares of the masses and the mixing angles, but the ordering of the masses (normal vs inverted) and whether neutrinos are Dirac or Majorana particles remain open questions. Experiments searching for neutrinoless double beta decay aim to determine Majorana character and constrain the absolute mass scale.

Detectors and experiments: Neutrinos are detected by observing rare interactions such as inverse beta decay or neutrino-electron scattering, typically in large volumes of water, ice, scintillator, or liquid argon. Notable experiments include Super-Kamiokande, Sudbury Neutrino Observatory, Borexino, and IceCube, with forthcoming projects like DUNE and JUNO aimed at resolving remaining questions about mass ordering, CP violation in the lepton sector, and high-energy astrophysical neutrinos.