Published January 1, 2014 | Version v1
Journal article Open

Measurement of the TeV atmospheric muon charge ratio with the complete OPERA data set

Creators

  • 1. Russian Acad Sci, INR, 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-119991 Moscow, Russia
  • 4. Kobe Univ, Kobe, Hyogo 6578501, Japan
  • 5. Univ Bern, LHEP, Albert Einstein Ctr Fundamental Phys, CH-3012 Bern, Switzerland
  • 6. METU, TR-06531 Ankara, Turkey
  • 7. Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy
  • 8. Univ Hamburg, D-22761 Hamburg, Germany
  • 9. Russian Acad Sci, LPI, RUS-119991 Moscow, Russia
  • 10. JINR, RUS-141980 Dubna, Russia
  • 11. Ist Nazl Fis Nucl, Lab Nazl Gran Sasso, I-67010 Laquila, Italy
  • 12. Univ Savoie, CNRS, IN2P3, LAPP, F-74941 Annecy Le Vieux, France

Description

The OPERA detector, designed to search for nu(mu) -> nu(tau) oscillations in the CNGS beam, is located in the underground Gran Sasso laboratory, a privileged location to study TeV-scale cosmic rays. For the analysis here presented, the detector was used to measure the atmospheric muon charge ratio in the TeV region. OPERA collected charge-separated cosmic ray data between 2008 and 2012. More than 3 million atmospheric muon events were detected and reconstructed, among which about 110000 multiple muon bundles. The charge ratio R-mu = N-mu+/N-mu- was measured separately for single and for multiple muon events. The analysis exploited the inversion of the magnet polarity which was performed on purpose during the 2012 Run. The combination of the two data sets with opposite magnet polarities allowed minimizing systematic uncertainties and reaching an accurate determination of the muon charge ratio. Data were fitted to obtain relevant parameters on the composition of primary cosmic rays and the associated kaon production in the forward fragmentation region. In the surface energy range 1-20 TeV investigated by OPERA, R-mu is well described by a parametric model including only pion and kaon contributions to themuon flux, showing no significant contribution of the prompt component. The energy independence supports the validity of Feynman scaling in the fragmentation region up to 200 TeV/nucleon primary energy.

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