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OPERA (Oscillation Project with Emulsion-tRacking Apparatus)

OPERA (Oscillation Project with Emulsion-tRacking Apparatus) was a long baseline neutrino oscillation experiment to search for the appearance of tau neutrinos in the muon neutrino beam from CERN to the Gran Sasso (CNGS) in Italy. A few muon neutrinos produced at CERN are converted to tau neutrinos on their 730 km flight through the earth’s crust to the Gran Sasso. The signature for a tau neutrino is the observation of the decay of a short-lived charged tau lepton, which was produced in a charge current interaction in the OPERA detector.

The target modules are built from planes containing the basic OPERA detector unit, the lead/emulsion brick. A brick consists of 57 nuclear emulsions interleaved with 56 lead plates of 1 mm thickness. The bricks are about 12 cm wide, 10 cm high, and the thickness in beam direction is about 8 cm, corresponding to 10 radiation lengths. In total, the two target modules contain about 150000 bricks. Behind each brick plane, a plane of horizontal and vertical scintillator strips is mounted (Target Tracker), mainly used to predict the brick, in which a neutrino interaction occurred and to register the precise time of the event. The signature for tau neutrino appearance is the observation of the decay of a short-lived charged tau lepton produced by a charged current interaction. A brick containing a neutrino interaction is removed from the detector with the Brick Manipulation System, the emulsions are developed at LNGS and then sent to the scanning labs in Europe and in Japan.

The OPERA experiment took data between 2008 and 2012, collecting about 17500 beam neutrino interactions in the target. About half of the events were scanned and analyzed until the end of 2012.

 

Most important results

  1. N. Agafonova et al. [OPERA Collaboration], "Evidence for  nu_mu->nu_tao appearance in the CNGS neutrino beam with the OPERA experiment," Phys. Rev. D 89 (2014) 051102 [arXiv:1401.2079 [hep-ex]].
  2. N. Agafonova et al. [OPERA Collaboration], "New results on nu_mu->nu_tao appearance with the OPERA experiment in the CNGS beam," JHEP 1311, 036 (2013) [Erratum-ibid.1404, 014 (2014)] [arXiv:1308.2553 [hep-ex]].
  3. N. Agafonova et al. [OPERA Collaboration], "Search for  nu_mu->nu_e oscillations with the OPERA experiment in the CNGS beam," JHEP 1307, 004 (2013) [Addendum-ibid.1307, 085 (2013)] [arXiv:1303.3953 [hep-ex]].
  4. T. Adam et al. [OPERA Collaboration], "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam using the 2012 dedicated data," JHEP 1301(2013) 153 [arXiv:1212.1276 [hep-ex]].
  5. N. Agafonova et al. [OPERA Collaboration], "Search for nu_mu->nu_tao  oscillation with the OPERA experiment in the CNGS beam," New J. Phys. 14 (2012) 033017.
  6. T. Adam et al. [OPERA Collaboration], "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam," JHEP 1210 (2012) 093 [arXiv:1109.4897[hep-ex]].
  7. N. Agafonova et al. [OPERA Collaboration], "Momentum measurement by the Multiple Coulomb Scattering method in the OPERA lead emulsion target," New J. Phys. 14 (2012) 013026 [arXiv:1106.6211 [physics.ins-det]].
  8. N. Agafonova et al. [ OPERA Collaboration ], "Study of neutrino interactions with the electronic detectors of the OPERA experiment," New J. Phys. 13 (2011) 053051.[arXiv:1102.1882 [hep-ex]].
  9. N. Agafonova et al. [OPERA Collaboration], "Measurement of the atmospheric muon charge ratio with the OPERA detector," Eur. Phys. J. C 67 (2010) 25 [arXiv:1003.1907 [hep-ex]].
  10. N. Agafonova et al. [OPERA Collaboration], "Observation of a first  candidate in the OPERA experiment in the CNGS beam," Phys. Lett. B 691 (2010) 138. [arXiv:1006.1623[hep-ex]].
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