 Schematic overview of the DONUT detector DONUT (Direct Observation of the NU Tau, E872) was an experiment at Fermilab dedicated to the search for tau neutrino interactions. Even though the detector operated only during a few months in the summer of 1997, it was largely successful. By detecting the tau neutrino, it confirmed the existence of the last lepton predicted by the Standard Model. Image File history File links No higher resolution available. ...
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Aerial view of the Fermilab site. ...
For other uses, see Neutrino (disambiguation). ...
The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...
Principle In DONUT, protons accelerated by the Tevatron were used to produce tau neutrinos via decay of charmed mesons. After eliminating as many unwanted background particles as possible by a system of magnets and bulk matter (mostly iron and concrete), the beam passed through several sheets of nuclear emulsion. In very rare cases one of the neutrinos would interact in the detector, producing electrically charged particles which left visible tracks in the emulsion and could be electronically registered by a system of scintillators and drift chambers. For alternative meanings see proton (disambiguation). ...
Tevatron is a circular particle accelerator (or synchrotron) at the Fermi National Accelerator Laboratory in Batavia, Illinois. ...
The charm quark is a second-generation quark with a charge of +(2/3)e. ...
A solid state nuclear track detector or SSNTD (also known as an etched track detector or a dielectric track detector, DTD) is a sample of a solid material (photographic emulsion, crystal, glass or plastic) exposed to nuclear radiation (neutrons or charged particles, occasionally also gamma rays), chemically etched, and examined...
A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ...
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Using the electronic information, possible neutrino interactions were identified and selected for further analysis. This meant photographically developing the emulsion sheets so any traces left by particles passing through them would show up as a small black dot. By connecting these dots across subsequent sheets, the path that each particle had taken was reconstructed and likely neutrino interactions identified. The characteristic properties of tau neutrino interactions were that several tracks suddenly appeared without any leading up to them and that one of those tracks would show a "kink" after a few millimeters, indicating decay of a tau lepton. DONUTS ARE AWESOME. A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ...
The tau lepton (often called the tau or occasionally the tauon) is a negatively charged elementary particle with a lifetime of 3×10−13 seconds and a high mass of 1777 MeV (compared to 939 MeV for protons and 0. ...
Result In July 2000, the DONUT collaboration announced the first observation of tau neutrino interactions. Even though this result was based on only four events, the signal largely exceeded the expected background (< 0.2 events) and is therefore considered valid. Its significance lies in the fact that the tau neutrino had so far remained the only particle of the Standard Model that had not been directly observed except for the Higgs boson. The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...
The Higgs boson, also known as the God particle, is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. ...
Other than the result itself, DONUT also allowed validation of new techniques for high energy neutrino detection, notably the Emulsion Cloud Chamber, in which nuclear emulsion sheets are interspersed with layers of iron, leading to an increase in the number of interactions. Observation of tau neutrinos also plays an important role in some neutrino oscillation experiments. Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ...
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