/ Astrophysics

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

Published in: Eur.Phys.J.
Year: 2014
Vol.: C74
Page No: 2933
Pages: 9
Year: 2014

Abstract: The OPERA detector, designed to search for ν μ → ν τ 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 μ ≡ N μ + / N μ − was measured separately for single and for multiple muon events. The anal- ysis exploited the inversion of the magnet polarity which was performed on purpose during the 2012 Run. The com- bination of the two data sets with opposite magnet polarities allowedminimizingsystematicuncertaintiesandreachingan accurate determination of the muon charge ratio. Data were fittedtoobtainrelevant parametersonthecompositionofpri- mary cosmic rays and the associated kaon production in the forward fragmentation region. In the surface energy range 1–20 TeV investigated by OPERA, R μ is well described by a parametric model including only pion and kaon contribu- tions to the muon 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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DOI: 10.1140/epjc/s10052-014-2933-0