![]() At energies above 5 MeV, solar neutrino oscillation actually takes place in the Sun through a resonance known as the MSW effect, a different process from the vacuum oscillation described later in this article. Solar neutrinos have energies below 20 MeV. Many subsequent radiochemical and water Cherenkov detectors confirmed the deficit, but neutrino oscillation was not conclusively identified as the source of the deficit until the Sudbury Neutrino Observatory provided clear evidence of neutrino flavor change in 2001. This gave rise to the solar neutrino problem. The first experiment that detected the effects of neutrino oscillation was Ray Davis' Homestake experiment in the late 1960s, in which he observed a deficit in the flux of solar neutrinos with respect to the prediction of the Standard Solar Model, using a chlorine-based detector. Because current detectors have energy uncertainties of a few percent, it is satisfactory to know the distance to within 1%. The limiting factor in measurements is the accuracy with which the energy of each observed neutrino can be measured. The preferred distance depends on the most common energy, but the exact distance is not critical as long as it is known. (Details in § Propagation and interference below.) Neutrino sources and detectors are far too large to move, but all available sources produce a range of energies, and oscillation can be measured with a fixed distance and neutrinos of varying energy. ![]() Neutrino oscillation is a function of the ratio L⁄ E, where L is the distance traveled and E is the neutrino's energy. McDonald for their early pioneering observations of these oscillations. The 2015 Nobel Prize in Physics was shared by Takaaki Kajita and Arthur B. Observations Ī great deal of evidence for neutrino oscillation has been collected from many sources, over a wide range of neutrino energies and with many different detector technologies. The experimental discovery of neutrino oscillation, and thus neutrino mass, by the Super-Kamiokande Observatory and the Sudbury Neutrino Observatories was recognized with the 2015 Nobel Prize for Physics. In particular, it implies that the neutrino has a non-zero mass, which requires a modification to the Standard Model of particle physics. Neutrino oscillation is of great theoretical and experimental interest, as the precise properties of the process can shed light on several properties of the neutrino. Most notably, the existence of neutrino oscillation resolved the long-standing solar neutrino problem. įirst predicted by Bruno Pontecorvo in 1957, neutrino oscillation has since been observed by a multitude of experiments in several different contexts. The probability of measuring a particular flavor for a neutrino varies between three known states, as it propagates through space. Some are antimatter versions.Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a specific lepton family number ("lepton flavor": electron, muon, or tau) can later be measured to have a different lepton family number. They come in different types and can be thought of in terms of flavors, masses, and energies. Physicist Enrico Fermi popularized the name “neutrino”, which is Italian for “little neutral one.” Neutrinos are denoted by the Greek symbol ν, or nu (pronounced “new”). To increase the odds of seeing them, scientists build huge detectors and create intense sources of neutrinos. Most neutrinos will pass through Earth without interacting at all. This weak force is important only at very short distances, which means tiny neutrinos can skirt through the atoms of massive objects without interacting. The only ways they interact is through gravity and the weak force, which is, well, weak. While we keep learning more about neutrinos, with new answers come new mysteries. First predicted in 1930, they weren’t discovered in experiments until 1956, and scientists thought they were massless until even later. These little particles have an interesting history. ![]() Neutrinos come from all kinds of different sources and are often the product of heavy particles turning into lighter ones, a process called “decay.” They’re also extremely common-in fact, they’re the most abundant massive particle in the universe. They are the lightest of all the subatomic particles that have mass. Neutrinos are also incredibly small and light. But while electrons have a negative charge, neutrinos have no charge at all. Neutrinos are members of the same group as the most famous fundamental particle, the electron (which is powering the device you’re reading this on right now). A neutrino is a particle! It’s one of the so-called fundamental particles, which means it isn’t made of any smaller pieces, at least that we know of.
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