#The neutrino is verification#

In the atmosphere, production ratio of the muon neutrino and electron neutrino is roughly 2 to 1. Zenith angle distribution of the muon neutrinos, generated by primary cosmic rays interacting with the Earth's atmosphere. It was the first experimental indication of minuscule, albeit non-zero, mass differences in neutrino generations. Neutrino oscillation causes some of the muon neutrinos changing into tau neutrinos which can not be observed. The zenith-angle distribution of atmoshperic neutrino showed that the number of upward-going muon neutrinos, generated on the other side of the Earth, is half of the number of downward-going ones. Neutrino oscillation –a consequence of the finite masses of neutrinos and of the mixing of their flavors– was discovered via Super-Kamiokande collaboration (1998), through the observation of neutrinos produced by primary cosmic rays interacting with the Earth's atmosphere.

#The neutrino is verification#

Discovery of neutrino oscillation and its verification The possibility of mixing of neutrino flavors was first proposed by Z. Hence, this periodic change of neutrino flavors is called neutrino oscillation.

For example, if 100% pure muon neutrinos are generated by an accelerator, they transform into tau neutrinos after covering a certain distance and then revert to their original flavor (muon neutrinos). The difference in their extremely small masses causes neutrinos to change flavors during flight. Each of neutrino forms a counterpart with a negatively-charged lepton. Neutrinos belong to lepton, whose charge is zero. Quarks and leptons are fundamental constituents of matter, which have both three generations. Each type of neutrino has a corresponding antiparticle these are called antineutrinos. There are three known types (generations or flavors) of neutrinos –electron neutrinos(ν e), muon neutrinos(ν μ), and tau neutrinos(ν τ)– corresponding to their charged counterparts. Their masses are extraordinarily small –less than 1/1,000,000 of the masses of electrons and the lightest quarks. It is extremely difficult to detect neutrinos because they can penetrate ordinary matter without any trace or disturbance. Cowan a quarter of a century later (1956) they conducted an experiment using a reactor as an intense source of neutrinos. The existence of neutrinos was verified by F. Pauli in 1930, to explain the beta-decay of atomic nuclei, and the phenomena was formulated beautifully by E.Fermi (1934). Their existence was first postulated by W.E. These are fundamental issues in the field of elementary particle physics, which may provide the key to understanding the evolution of our matter-dominated universe.Īre mysterious subatomic particles having a neutral charge. We can also determine the extent of mixing of neutrino flavors. In particular, we can determine their relative lightness, as compared to other elementary particles such as electrons or quarks, the latter of which are part of the nucleus.

By investigating neutrino oscillation, we can uncover the mysterious characteristics of neutrinos. This phenomenon is known as neutrino oscillation. As the neutrinos traverse the Japanese Archipelago at virtually the speed of light, a change occurs in an essential characteristic –the generation or flavor– of the neutrinos. High-intensity neutrino beams are directed from the Japan Proton Accelerator Research Complex (J-PARC) at Tokai village (Ibaraki Prefecture) towards Super-Kamiokande –the world's largest underground neutrino detector– located at Hida city (Gifu Prefecture). Is a Japanese-led multinational physics experiment.

Introduction to T2K：Clarifying the picture of neutrino mass and mixing Tokai to Kamioka (T2K)