The tau neutrino or tauon neutrino is an

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a c ...

which has the symbol and zero

electric charge Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and ...

. Together with the tau (), it forms the third

generation A generation is all of the people born and living at about the same time, regarded collectively. It also is "the average period, generally considered to be about 20–⁠30 years, during which children are born and grow up, become adults, and b ...

lepton In particle physics, a lepton is an elementary particle of half-integer spin (Spin (physics), spin ) that does not undergo strong interactions. Two main classes of leptons exist: electric charge, charged leptons (also known as the electron-li ...

s, hence the name tau

neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...

. Its existence was immediately implied after the tau particle was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC– LBL group. The discovery of the tau neutrino was announced in July 2000 by the DONUT collaboration (Direct Observation of the Nu Tau). In 2024, the

IceCube Neutrino Observatory The IceCube Neutrino Observatory (or simply IceCube) is a neutrino observatory developed by the University of Wisconsin–Madison and constructed at the Amundsen–Scott South Pole Station in Antarctica. The project is a recognized CERN experime ...

published findings of seven astrophysical tau neutrino candidates. As of 2022 they have been called the "least studied particle in the standard model" because of their low cross section, difficulty of production, and difficulty to distinguish from other neutrino flavors. One review argues they are worth studying more in order to finally completely measure their properties, test our knowledge of neutrino mixing, probe possible anomalies, and make full use of experiments that are sensitive to tau neutrinos in any case.

Discovery

The DONUT experiment from

Fermilab Fermi National Accelerator Laboratory (Fermilab), located in Batavia, Illinois, near Chicago, is a United States Department of Energy United States Department of Energy National Labs, national laboratory specializing in high-energy particle phys ...

was built during the 1990s to specifically detect the tau neutrino. These efforts came to fruition in July 2000, when the DONUT collaboration reported its detection. The tau neutrino is last of the leptons, and is the second most recent discovered particle of the

Standard Model The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

(i.e., it was observed 12 years before the discovery of the

Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...

in 2012).

Detection

Several natural high-energy tau neutrinos have been successfully identified by the IceCube Neutrino Observatory. Tau neutrinos are hard to distinguish from electron neutrinos in ice-based neutrino detectors because they produce similar patterns of photons as electron neutrinos do. Electron neutrinos and tau neutrinos, in contrast to muon neutrinos, both cause sphere-shaped photon detection patterns in ice. When an electron neutrino interacts with an ice-based detector, it produces an electron, which does not travel far before hitting an atom and releasing a spherical photon pattern. Tau neutrinos produce a tau particle, which emits a ball of photons twice – when it is produced and when it decays. However, these one-ball and two-ball patterns are very difficult to distinguish except for very high-energy tau neutrinos, which cause the tau particle to travel further between production and decay, making the pattern more distinguishable from a sphere.

References

{{particles Neutrinos Leptons Elementary particles 2000 in science

Discovery

Detection

See also

References