Neutrinos are one of the fundamental particles making up the universe.Elementary particles include particles that make up matter (such as quarks,elec-trons, and neutrinos), gauge bosons which propagate force,and Higgs bosons which are related to mass(Figure 1).Electrons and neutrinos are collectivelycalled "leptons." Leptons include three types (flavors)of charged particles having properties similar to those of the electron，namely, the electron，muon (u),and tau (z).There are also three flavors of neutral lep-tons: the electron neutrino，muon neutrino, and tauneutrino.Thought for a long time to have a mass ofzero，neutrinos interact with particles like quarks and electrons that make up matter only through "weak interaction.” As a result, the probability of neutrino in-teraction with matter is extremely small, making them difficult to detect.Research with the aim of explaining this property continues to this day.
展开▼
