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DONUT
DONUT
(Direct observation of the nu tau, E872) was an experiment at Fermilab
Fermilab
dedicated to the search for tau neutrino interactions. The detector operated during a few months in the summer of 1997, and successfully detected the tau neutrino.[1] It confirmed the existence of the last lepton predicted by the Standard Model.[2] The data from the experiment was also used to put an upper limit on the tau neutrino magnetic moment[3] and measure its interaction cross section.[4]

Contents

1 Principle 2 Result 3 See also 4 References 5 External links

Principle[edit] In DONUT, protons accelerated by the Tevatron
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.[1] 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.[1] Result[edit] In July 2000, the DONUT
DONUT
collaboration announced the first observation of tau neutrino interactions. Even though this result was based on only four events, the signal was far in excess of the expected background (< 0.2 events) and is therefore valid. Its significance lies in the fact that the tau neutrino had so far remained the only particle of the Standard Model
Standard Model
that had not been directly observed except for the Higgs boson.[2] Other than the result itself, DONUT
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. See also[edit]

Nu (letter)

References[edit]

^ a b c K. Kodama et al. ( DONUT
DONUT
Collaboration) (2001). "Observation of tau neutrino interactions". Physics Letters B. 504 (3): 218. arXiv:hep-ex/0012035 . Bibcode:2001PhLB..504..218D. doi:10.1016/S0370-2693(01)00307-0 .  ^ a b "Physicists Find First Direct Evidence for Tau Neutrino at Fermilab" (Press release). Fermilab. 20 July 2000.  ^ K. Kodama et al. ( DONUT
DONUT
Collaboration) (2008). "A first measurement of the interaction cross section of the tau neutrino". Physical Review D. 78 (5): 052002. arXiv:0711.0728 . Bibcode:2008PhRvD..78e2002K. doi:10.1103/PhysRevD.78.052002.  ^ R. Schwienhorst et al. ( DONUT
DONUT
Collaboration) (2001). "A new upper limit for the tau-neutrino magnetic moment". Physics Letters B. 513: 23. arXiv:hep-ex/0102026 . Bibcode:2001PhLB..513...23D. doi:10.1016/S0370-2693(01)00746-8 . 

External links[edit]

DONUT
DONUT
home page

v t e

Neutrino detectors, experiments, and facilities

Discoveries

Cowan–Reines (ν e) Lederman–Schwartz–Steinberger (ν μ) DONUT
DONUT
(ν τ) Neutrino oscillation SN 1987 neutrino burst

Operating (Divided by primary neutrino source)

Astronomical

ANITA ANTARES BDUNT BNO Borexino GNO HALO ICARUS IceCube LVD MARIACHI NARC NESTOR Project NEVOD RICE Super-Kamiokande SNEWS

Reactor

Daya Bay Double Chooz KamLAND RENO

Accelerator

CNGS MicroBooNE MINERνA MiniBooNE NA61/SHINE NOνA NuMI T2K WITCH

0νββ

CUORE EXO GERDA KamLAND-Zen MAJORANA

Other

KATRIN

Construction

ARA ARIANNA JUNO KM3NeT SNO+ SuperNEMO

Retired

AMANDA CDHS CHOOZ DONUT GALLEX Gargamelle Homestake IMB K2K Kamiokande KARMEN MACRO MINOS MINOS+ NEMO OPERA KGF LSND SAGE SciBooNE SNO Soudan 2

Proposed

ANNIE DUNE Hyper-Kamiokande INO LAGUNA LENA Neutrino Factory nEXO Nucifer UNO JEM-EUSO

Cancelled

DUMAND Project Long Baseline Neutrino Experiment

See also

List of neutrin

.