Estimations of the muon content of cosmic ray air showers between 10 PeV and 1 EeV from KASCADE-Grande data

Abstract

Measurements of KASCADE-Grande on the muon size in high energy extensive air showers (EAS) have provided evidence that the actual attenuation length of shower muons in the atmosphere is larger than the expectations from the hadronic interaction models QGSJET-II-04, EPOS-LHC and SIBYLL 2.3. This discrepancy is related to a deficient description of the shower muon content with atmospheric depth by Monte Carlo (MC) models. To further explore the origin of the above anomaly, we have investigated the muon size as a function of the primary energy at different zenith angles using data from the KASCADE-Grande experiment. The procedure consisted in comparing the measured muon number flux against the predictions of a reference cosmic ray energy spectrum and from the observed difference to estimate the data/MC muon ratio that best describe the measurements. The ratio is then applied to the MC simulations and from here, we estimate the muon content versus the primary energy. As a reference model, we employed the energy spectrum measured from the Pierre Auger observatory, while, for the different cosmic ray abundances, the GSF model. Results are presented using the QGSJET-II-04, EPOS-LHC, SIBYLL 2.3 and SIBYLL 2.3c models in the analysis procedure.

Results from recent analysis of KASCADE-Grande data

“…A further analysis is performed by investigating the muon content of air showers as a function of the primary energy in the interval from 10 16 to 10 18 eV and for different zenith angle ranges by means of KASCADE-Grande data [13]. We compared this estimation with the predictions of the muon content for the post-LHC hadronic interaction models including the new model of SIBYLL 2.3c.…”

“…5 (right). Applying the fitted shift to the true N µ of the Monte Carlo simulations [13], we obtained the actual muon content: Figure 6 presents the estimated log 10 [N µ /E(GeV)] from the measured data as a function of the primary energy of log 10 (E/GeV) for each zenith angle interval using fits with different hadronic interaction models. The results with their respective statistical and systematic uncertainties are compared with the fit to the predictions of the post-LHC hadronic models for H (blue), Fe (red), and the reference composition model (dashed line).…”

“…Right: Distribution of the measured number of muons N µ (black dots) and the result of the fit (red lines) using QGSJET-II-04. Vertical events (θ < 21.78 • ) are shown here as an example [13].…”