OPERA experiment
The Oscillation Project with Emulsion-Racking Apparatus (OPERA) is an instrument used in a scientific experiment for detecting tau neutrinos from muon neutrino oscillations. The experiment 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.
The process starts with protons from the SPS at CERN being fired in pulses at a carbon target to produce pions and kaons. These particles decay to produce muons and neutrinos.[1]
On 31 May 2010, OPERA researchers observed the first tau neutrino candidate event in a muon neutrino beam.[2]
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[edit] Detector
OPERA, in Hall C of the Gran Sasso underground labs, was built in 2003–2008. The taus 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.[3]
[edit] Faster-than-light neutrino anomaly
In September 2011, OPERA researchers observed muon neutrinos apparently traveling faster than the speed of light. On 22 February 2012, it was reported that sources familiar with the OPERA experiment are now blaming the original result on a loose fibre optic cable connecting a GPS receiver to an electronic card in a computer.[4] On 16 March 2012, a report announced that an independent experiment in the same laboratory, also using the CNGS neutrino beam, but this time the ICARUS detector, found no discernible difference between the speed of a neutrino and the speed of light.[5][6][7]
[edit] References
- ^ Faster than the speed of light?, Posted on November 18, 2011 by Jim Al-Khalili
- ^ N. Agafonova et al. (OPERA Collaboration) (2010). "Observation of a first ντ candidate event in the OPERA experiment in the CNGS beam". Physics Letters B 691 (3): 138–145. arXiv:1006.1623. Bibcode 2010PhLB..691..138A. doi:10.1016/j.physletb.2010.06.022.
- ^ "Opera – The Opera Detector". http://operaweb.lngs.infn.it/spip.php?rubrique39. Retrieved 25 Sep 2011.
- ^ "'Faster than light' measurement blamed on loose cable". http://www.cbc.ca/news/technology/story/2012/02/22/technology-faster-than-light-neutrinos.html. Retrieved 22 February 2012.
- ^ Antonello, M. et al. (16 March 2012). "Measurement of the neutrino velocity with the ICARUS detector at the CNGS beam". ArXiv. http://arxiv.org/abs/1203.3433. Retrieved 17 March 2012.
- ^ Associated Press (16 March 2012). "Einstein Proved Right in Retest of Neutrinos’ Speed". New York Times. http://www.nytimes.com/2012/03/17/science/einstein-proved-right-in-retest-of-neutrinos-speed.html. Retrieved 17 March 2012.
- ^ Palmer, Jason (16 March 2012). "Neutrinos clocked at light-speed in new Icarus test". BBC. http://www.bbc.co.uk/news/science-environment-17364682. Retrieved 17 March 2012.
[edit] External links
- Opera Main Page
- CERN: First Appearance Of Tau Neutrino
- The appearance of the tau-neutrino
- OPERA publications
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