OPERA Experiment
Encyclopedia
The Oscillation Project with Emulsion-tRacking Apparatus (OPERA) is a scientific experiment for detecting tau neutrinos from muon neutrino
oscillations
. It is a collaboration between CERN
in Geneva
, Switzerland
, and the Laboratori Nazionali del Gran Sasso
(LNGS) in Gran Sasso
, Italy
and uses the CERN Neutrinos to Gran Sasso
(CNGS) neutrino beam. On 31 May 2010, OPERA researchers observed the first tau neutrino candidate event in a muon neutrino beam. In September 2011, OPERA researchers observed muon neutrinos traveling apparently at faster
than the speed of light (see OPERA neutrino anomaly
).
resulting from the interaction of tau neutrinos are observed in "bricks" of photographic films (nuclear emulsion
) interleaved with lead sheets. Each brick weighs 8.3 kg; the two OPERA supermodules contain 150,000 bricks arranged into parallel walls interleaved with plastic scintillator
counters. Each supermodule is followed by a magnetic spectrometer
for momentum and charge identification of penetrating particles. During data collection, a neutrino interaction and its corresponding brick are tagged in real time by the scintillators and spectrometers. These bricks are extracted from the walls asynchronously with respect to the beam for film development, scanning and for the topological and kinematic search of tau decays.
Muon neutrino
The muon neutrino is a subatomic lepton elementary particle which has the symbol and no net electric charge. Together with the muon it forms the second generation of leptons, hence its name muon neutrino. It was first hypothesized in the early 1940s by several people, and was discovered in 1962 by...
oscillations
Neutrino oscillation
Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvowhereby a neutrino created with a specific lepton flavor can later be measured to have a different flavor. The probability of measuring a particular flavor for a neutrino varies periodically as it propagates...
. It is a collaboration between CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
in Geneva
Geneva
Geneva In the national languages of Switzerland the city is known as Genf , Ginevra and Genevra is the second-most-populous city in Switzerland and is the most populous city of Romandie, the French-speaking part of Switzerland...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, and the Laboratori Nazionali del Gran Sasso
Laboratori Nazionali del Gran Sasso
Laboratori Nazionali del Gran Sasso is a particle physics laboratory of the INFN, situated near the Gran Sasso mountain in Italy, between the towns of L'Aquila and Teramo, about 120 km from Rome. In addition to a surface portion of the laboratory, there are extensive underground facilities...
(LNGS) in Gran Sasso
Gran Sasso
Gran Sasso d'Italia is a mountain located in the Abruzzo region of central Italy. The Gran Sasso forms the centerpiece of the Gran Sasso e Monti della Laga National Park which was established in 1993 and holds the highest mountains in continental Italy south of the Alps and is part of the...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
and uses the CERN Neutrinos to Gran Sasso
CERN Neutrinos to Gran Sasso
The CERN Neutrinos to Gran Sasso project is a physics project of the European Organization for Nuclear Research . The aim of the project is to analyse the hypothesis of neutrino oscillation by directing a beam of neutrinos from CERN's facilities to the detector of the OPERA experiment at the Gran...
(CNGS) neutrino beam. On 31 May 2010, OPERA researchers observed the first tau neutrino candidate event in a muon neutrino beam. In September 2011, OPERA researchers observed muon neutrinos traveling apparently at faster
Faster-than-light
Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....
than the speed of light (see OPERA neutrino anomaly
OPERA neutrino anomaly
The OPERA neutrino anomaly is the detection of apparently faster-than-light neutrinos by the OPERA experiment as publicly announced in September 2011. The detection is anomalous because speeds exceeding that of light in a vacuum are generally thought to violate special relativity, a prevailing...
).
Detector
OPERA, in Hall C of the Gran Sasso underground labs, was built in 2003-2008. The tausTau lepton
The tau , also called the tau lepton, tau particle or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of . Together with the electron, the muon, and the three neutrinos, it is classified as a lepton...
resulting from the interaction of tau neutrinos are observed in "bricks" of photographic films (nuclear emulsion
Nuclear emulsion
In a Particle and Nuclear physics, a nuclear emulsion plate is a photographic plate with a particularly thick emulsion layer and with a very uniform grain size. Like bubble chambers, cloud chambers, and wire chambers nuclear emulsion plates record the tracks of charged particles passing through...
) interleaved with lead sheets. Each brick weighs 8.3 kg; the two OPERA supermodules contain 150,000 bricks arranged into parallel walls interleaved with plastic scintillator
Scintillator
A scintillator is a special material, which exhibits scintillation—the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e., reemit the absorbed energy in the form of light...
counters. Each supermodule is followed by a magnetic spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
for momentum and charge identification of penetrating particles. During data collection, a neutrino interaction and its corresponding brick are tagged in real time by the scintillators and spectrometers. These bricks are extracted from the walls asynchronously with respect to the beam for film development, scanning and for the topological and kinematic search of tau decays.