Muon content of extensive air showers: comparison of the energy spectra obtained by the Sydney University Giant Air-shower Recorder and by the Pierre Auger Observatory

Understand

The Sydney University Giant Air-shower Recorder (SUGAR) measured the energy spectrum of ultra-high-energy cosmic rays reconstructed from muon-detector readings, while the Pierre Auger Observatory, looking at the same Southern sky, uses the calorimetric fluorescence method for the same purpose.

• Comparison of their two spectra allows us to reconstruct the empirical dependence of the number of muons in the shower on the primary energy for energies between $10^{17}$ and $10^{18.5}$ eV.
• We compare this dependence with the predictions of hadronic interaction models \mbox{QGSJET-II-04} and \mbox{EPOS-LHC}.
• The empirically determined number of muons with energies above 0.75 GeV exceeds the simulated one by the factors $\sim$1.67 and $\sim$1.28 for $10^{17}$ eV proton and iron primaries, respectively.