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CERN Neutrinos to Gran Sasso

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CERN Neutrinos to Gran Sasso Underground Structures
CERN Neutrinos to Gran Sasso Underground Structures

TheCERN Neutrinos to Gran Sasso(CNGS) project was a physics project of theEuropean Organization for Nuclear Research(CERN). The aim of the project was to analyse the hypothesis ofneutrino oscillationby directing abeamofneutrinosfrom CERN's facilities to the detector of theOPERA experimentat theGran Sasso National Laboratory(LNGS), located in theGran Sassomountain inItaly.The CNGS facility was housed in a tunnel which diverged from one of the SPS–LHC transfer tunnels, at theFranco–Swissborder nearGeneva.[1]It used theSuper Proton Synchrotron(SPS) accelerator as a source of high-energyprotons.

History

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The magnetic horn being installed in the CNGS target chamber

Approval for the CNGS project was signed by the CERN Council in December 1999,[2]with civil engineering on the project starting the following September.[3]Construction of the tunnels and service caverns was completed in mid-2004, with equipment installation completed in summer 2005 and commissioning being carried out throughout spring 2006. The firstproton beamwas sent to the target on 11 July 2006, with the CNGS facility being approved for physics operations on 18 August 2006. CNGS ceased operation in 2012. The tunnel was then repurposed for theAWAKEexperiment, which became operational in 2016.

Function

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Aprotonbeam was taken from the SPS at400GeVand is made to collide with agraphitetarget within the CNGS tunnel. The resulting particles, most importantlykaonsandpionsamong many other particles, were then focused bymagnetic lensingand travelled 1 kilometre (0.62 mi) down the CNGS tunnel in a vacuum tube. These particles are naturally unstable, and their decay products includemuonsandmuon neutrinos.All particles except neutrinos (protons, muons, pion, kaon...) stop near the end of the tunnel. The neutrinos continue their flight unaffected, as they rarely interact with matter. The number of muons was measured at this point, which gave an indication of the beam's profile and intensity. This beam then passed 732 kilometres (455 mi) through thecrustof theEarthand it is expected that during flight some of the muon neutrinos convert into other neutrino types such astau neutrinos.[1]Once the beam arrived at Gran Sasso, theOPERAandICARUSexperiments were used to detect the neutrinos.

Results

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The first candidates for neutrino oscillation to tau neutrinos were announced in May 2010 by the OPERA experiment.[4]In total five tau neutrinos were observed,[5]consistent with the expectations from the theory ofneutrino oscillation.

On 22 September 2011, the OPERA collaboration garnered international attention when they released apreprint[6]reporting theFaster-than-light neutrino anomaly,wherein neutrinos were measured to be travelling, on average, atfaster-than-lightspeed.[7]On 24 February 2012, the team said they had discovered two problems with their previous test, muddying the validity of the previous result.[8]The preprint has been modified to account for these facts, and indeed the measurement of the neutrino speed, there reported, agrees with the velocity of the light.

References

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  1. ^ab"General Description of the CERN Project for a Neutrino Beam"(PDF).
  2. ^"CNGS project Overview".
  3. ^"CERN Neutrinos to Gran Sasso (CNGS): First Beam"(PDF).
  4. ^"Tau Neutrino embargo"(PDF).Archived fromthe original(PDF)on 2011-10-26.Retrieved2011-09-23.
  5. ^O'Luanaigh, C. (6 October 2015)."OPERA detects its fifth tau neutrino".Retrieved2017-02-08.
  6. ^T. Adamet al.(OPERA Collaboration) (22 September 2011). "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam".Journal of High Energy Physics.2012(10): 93.arXiv:1109.4897.Bibcode:2012JHEP...10..093A.doi:10.1007/JHEP10(2012)093.S2CID17652398.
  7. ^"Speed-of-light experiments give baffling result at Cern".BBC.22 September 2011.
  8. ^"Faster-than-light neutrinos could be down to bad wiring".BBC News.23 February 2012.
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