The KASCADE-Grande air shower experiment [1] consists of, among others, a large scintillator array for measurements of charged particles, N ch , and of an array of shielded scintillation counters used for muon counting, N µ . KASCADE-Grande is optimized for cosmic ray measurements in the energy range 10 PeV to about 2000 PeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. Following earlier studies of the all-particle and the elemental spectra reconstructed in the knee energy range from KASCADE data [2], we have now extended these measurements to beyond 200 PeV. By analysing the two-dimensional shower size spectrum N ch vs. N µ for nearly vertical events, we reconstruct the energy spectra of different mass groups by means of unfolding methods over an energy range where the detector is fully efficient. The procedure and its results, which are derived based on the hadronic interaction model QGSJET-II-02 and which yield a strong indication for a dominance of heavy mass groups in the covered energy range and for a knee-like structure in the iron spectrum at around 80 PeV, are presented. This confirms and further refines the results obtained by other analyses of KASCADE-Grande data, which already gave evidence for a knee-like structure in the heavy component of cosmic rays at about 80 PeV [3].
Recent results of the KASCADE-Grande experiment provided evidence for a mild knee-like struc-25 ture in the all-particle spectrum of cosmic rays at E = 10 16.92±0.10 eV, which was found to be due to a steepening in the flux of heavy primary particles. The spectrum of the combined components of light and intermediate masses was found to be compatible with a single power law in the energy range from 10 16.3 eV to 10 18 eV. In this paper, we present an update of this analysis by using data with increased statistics, originating both from a larger data set including more recent measure-30 ments and by using a larger fiducial area. In addition, optimized selection criteria for enhancing light primaries are applied. We find a spectral feature for light elements, namely a hardening at E = 10 17.08±0.08 eV with a change of the power law index from −3.25 ± 0.05 to −2.79 ± 0.08.
Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above 10 17 eV and zenith angles smaller than 45 • , we find that the radio wavefront of cosmic-ray air showers is of approximately hyperbolic shape. The simulations predict a slightly steeper wavefront towards East than towards West, but this asymmetry is negligible against the measurement uncertainties of LOPES. At axis distances 50 m, the wavefront can be approximated by a simple cone. According to the simulations, the cone angle is clearly correlated with the shower maximum. Thus, we confirm earlier predictions that arrival time measurements can be used to study the longitudinal shower development, but now using a realistic wavefront. Moreover, we show that the hyperbolic wavefront is compatible with our measurement, and we present several experimental indications that the cone angle is indeed sensitive to the shower development. Consequently, the wavefront can be used to statistically study the primary composition of ultra-high energy cosmic rays. At LOPES, the experimentally achieved precision for the shower maximum is limited by measurement uncertainties to approximately 140 g/cm 2 . But the simulations indicate that under better conditions this method might yield an accuracy for the atmospheric depth of the shower maximum, X max , better than 30 g/cm 2 . This would be competitive with the established air-fluorescence and air-Cherenkov techniques, where the radio technique offers the advantage of a significantly higher duty-cycle. Finally, the hyperbolic wavefront can be used to reconstruct the shower geometry more accurately, which potentially allows a better reconstruction of all other shower parameters, too.
The 'KASCADE Cosmic ray Data Centre' is a web portal (https://kcdc.ikp.kit.edu), where the data of the astroparticle physics experiment KASCADE-Grande are made available for the interested public. The KASCADE experiment was a large-area detector for the measurement of high-energy cosmic rays via the detection of extensive air showers. The multi-detector installations KASCADE and its extension KASCADE-Grande stopped the active data acquisition in 2013 after more than 20 years of data taking. In several updates since our first release in 2013 with KCDC we provide the public measured and reconstructed parameters of more than 433 million air showers. In addition, KCDC provides meta data information and documentation to enable a user outside the community of experts to perform their own data analysis. Simulation data from three different high a
KASCADE and KASCADE-Grande were multi-detector installations to measure individual air showers of cosmic rays at ultra-high energy. Based on data sets measured by KASCADE and KASCADE-Grande, 90% C.L. upper limits to the flux of γ rays in the primary cosmic ray flux are determined in an energy range of 10 14 − 10 18 eV. The analysis is performed by selecting air showers with a low muon content as expected for gamma-ray induced showers compared to air showers induced by energetic nuclei. The best upper limit of the fraction of γ rays to the total cosmic ray flux is obtained at 3.7 × 10 15 eV with 1.1 × 10 −5 . Translated in an absolute γ-ray flux this sets constrains on some fundamental astrophysical models, such as the distance of sources for at least one of the IceCube neutrino excess models.
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