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Published January 1, 2013 | Version v1
Journal article Open

New results on nu(mu) -> nu(tau) appearance with the OPERA experiment in the CNGS beam

Creators

  • 1. Russian Acad Sci, INR Inst Nucl Res, RUS-117312 Moscow, Russia
  • 2. Ist Nazl Fis Nucl, Sez Napoli, I-80125 Naples, Italy
  • 3. Moscow MV Lomonosov State Univ, SINP MSU Skobeltsyn Inst Nucl Phys, RUS-119992 Moscow, Russia
  • 4. Kobe Univ, Kobe, Hyogo 6578501, Japan
  • 5. Univ Bern, Albert Einstein Ctr Fundamental Phys, High Energy Phys Lab, CH-3012 Bern, Switzerland
  • 6. Nagoya Univ, Nagoya, Aichi 4648602, Japan
  • 7. Univ Lyon 1, CNRS, IN2P3, IPNL, F-69622 Villeurbanne, France
  • 8. ETH, Inst Particle Phys, CH-8093 Zurich, Switzerland
  • 9. Middle E Tech Univ, METU, TR-06531 Ankara, Turkey
  • 10. Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy
  • 11. Univ Hamburg, D-22761 Hamburg, Germany
  • 12. Russian Acad Sci, LPI Lebedev Phys Inst, Moscow 119991, Russia
  • 13. Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Rome, Italy

Description

The OPERA neutrino experiment is designed to perform the first observation of neutrino oscillations in direct appearance mode in the nu(mu) -> nu(tau) channel, via the detection of the tau-leptons created in charged current nu(tau) interactions. The detector, located in the underground Gran Sasso Laboratory, consists of an emulsion/lead target with an average mass of about 1.2 kt, complemented by electronic detectors. It is exposed to the CERN Neutrinos to Gran Sasso beam, with a baseline of 730 km and a mean energy of 17 GeV. The observation of the first nu(tau) candidate event and the analysis of the 2008-2009 neutrino sample have been reported in previous publications. This work describes substantial improvements in the analysis and in the evaluation of the detection efficiencies and backgrounds using new simulation tools. The analysis is extended to a sub-sample of 2010 and 2011 data, resulting from an electronic detector-based pre-selection, in which an additional nu(tau) candidate has been observed. The significance of the two events in terms of a nu(mu) -> nu(tau) oscillation signal is of 2.40 sigma.

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