Search

KASCADE-Grande and its original array of KASCADE were dedicated to measure individual air showers of cosmic rays with great detail in the primary energy range of 100 TeV up to 1 EeV. The experiment has significantly contributed to investigations of the energy spectrum and chemical composition of cosmic rays in the transition region from galactic to extragalactic origin of cosmic rays as well as to the further development of hadronic interaction models through validity tests using the multi-detector information from KASCADE-Grande. Though the data accumulation was completed in 2013, the data analysis is still continuing. Recently, we investigate the reliability of the new hadronic interactions model of the Sibyll version 2.3d with the combined data from KASCADE and KASCADE-Grande, and compare it to the predictions of different hadronic interaction models. In addition, we update the web-based platform of the KASCADE Cosmic Ray Data Centre (KCDC), where now full datasets from KASCADE and KASCADE-Grande and the corresponding Monte-Carlo simulated events are available., Presented at the 37th International Cosmic Ray Conference (ICRC 2021)

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 with a deficient description of the shower muon content with atmospheric depth by 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 wanted 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.

The KASCADE and KASCADE-Grande experiments operated in KIT-Campus North, Karlsruhe (Germany) from 1993 to 2012. The two experiments studied primary cosmic rays in the energy range from 1014 eV to 1018 eV, investigating the change of slope of the spectrum detected at 2 - 4 × 1015 eV, the so called knee. We briefly review the performance of the experiments and then the main results obtained in the operation of both experiments: the test of hadronic interaction models, the all particle primary spectrum, the elemental composition of primary cosmic rays (with the first claim of a knee-like feature of the heavy primaries spectrum) and the search for large scale anisotropies.

LOPES, the LOFAR prototype station, was an antenna array for cosmic-ray air showers operating from 2003 - 2013 within the KASCADE-Grande experiment. Meanwhile, the analysis is finished and the data of air-shower events measured by LOPES are available with open access in the KASCADE Cosmic Ray Data Center (KCDC). This article intends to provide a summary of the achievements, results, and lessons learned from LOPES. By digital, interferometric beamforming the detection of air showers became possible in the radio-loud environment of the Karlsruhe Institute of Technology (KIT). As a prototype experiment, LOPES tested several antenna types, array configurations and calibration techniques, and pioneered analysis methods for the reconstruction of the most important shower parameters, i.e., the arrival direction, the energy, and mass-dependent observables such as the position of the shower maximum. In addition to a review and update of previously published results, we also present new results based on end-to-end simulations including all known instrumental properties. For this, we applied the detector response to radio signals simulated with the CoREAS extension of CORSIKA, and analyzed them in the same way as measured data. Thus, we were able to study the detector performance more accurately than before, including some previously inaccessible features such as the impact of noise on the interferometric cross-correlation beam. These results led to several improvements, which are documented in this paper and can provide useful input for the design of future cosmic-ray experiments based on the digital radio-detection technique., Comment: Accepted for publication by EPJ C

The `KASCADE Cosmic ray Data Centre' is a web portal (\url{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 of all its components end of 2012 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 energy interaction models have been made available as well as a compilation of measured and published spectra from various experiments. In addition, detailed educational examples shall encourage high-school students and early stage researchers to learn about astroparticle physics, cosmic radiation as well as the handling of Big Data and about the sustainable and public provision of scientific data., Comment: 16 pages, submitted to The European Physical Journal C

KASCADE-Grande was an air-shower experiment aimed to investigate cosmic rays between 1016 and 1018 eV. The instrument was located at the site of the Karlsruhe Institute of Technology, Germany at an altitude of 110 m a.s.l. and covered an area of 0.5 km2. KASCADE-Grande consisted of several detector systems dedicated to measure different components of the cosmic ray induced air showers, e.g. the muon content (Eth > 230 MeV) and the number of charged particles (Eth > 3 MeV) at ground, which are the basis for several energy and composition studies of cosmic rays. In this contribution, using these observables, the KASCADE-Grande data is divided into light and heavy mass groups and their respective muon densities are reconstructed at different zenith angle intervals. The results are compared with the expectations of the post-LHC hadronic-interaction models, EPOS-LHC and QGSJET-II-04, in order to test the validity of the model predictions.

The evolution of the muon content of very high energy air showers (EAS) in the atmosphere is investigated with data of the KASCADE-Grande observatory. For this purpose, the muon attenuation length in the atmosphere is obtained to $\Lambda_\mu = 1256 \, \pm 85 \, ^{+229}_{-232}(\mbox{syst})\, \mbox{g/cm}^2$ from the experimental data for shower energies between $10^{16.3}$ and $10^{17.0} \, \mbox{eV}$. Comparison of this quantity with predictions of the high-energy hadronic interaction models QGSJET-II-02, SIBYLL 2.1, QGSJET-II-04 and EPOS-LHC reveals that the attenuation of the muon content of measured EAS in the atmosphere is lower than predicted. Deviations are, however, less significant with the post-LHC models. The presence of such deviations seems to be related to a difference between the simulated and the measured zenith angle evolutions of the lateral muon density distributions of EAS, which also causes a discrepancy between the measured absorption lengths of the density of shower muons and the predicted ones at large distances from the EAS core. The studied deficiencies show that all four considered hadronic interaction models fail to describe consistently the zenith angle evolution of the muon content of EAS in the aforesaid energy regime., Comment: Published in Astroparticle Physics 95 (2017) 25-43

Muons in extensive air showers (EAS) are a sensitive probe for the primary cosmic ray mass and the physics of hadronic interactions at very high energies, hence it is important to precisely measure and carefully analyze this particular shower component. In practice, however, such measurements are difficult to carry out due to the penetrating nature of muons and their low density in the shower. This way just in a few experimental facilities the shower muon component has been measured event-by-event in combination with other EAS observables. One of them was the multicomponent air shower experiment KASCADE-Grande, which was designed to study cosmic rays in the energy interval from $1$ PeV to $1$ EeV and was located at the site of the Karlsruhe Institute of Technology, Germany at $110$ m a.s.l. In this work, we will present an analysis of the KASCADE-Grande data in terms of the muon content ($E_\mu > 230$ MeV) of cosmic-ray induced air showers as a function of the primary energy (E = $10$ PeV $- 1$ EeV) and the zenith angle ($< 35^\circ$). We test also the predictions on the shower muon content of the post-LHC hadronic interaction models EPOS-LHC, QGSJET-II-04, SIBYLL 2.3 and SIBYLL 2.3c by comparing the model expectations with experimental results.

KASCADE, together with its extension KASCADE-Grande measured individual air showers of cosmic rays in the primary energy range of 100 TeV to 1 EeV. The data collection was fully completed at the end of 2013 and the experiment was dismantled. However, the data analysis is still in progress. Recently, we published a new result on upper limits to the flux of ultra-high energy gamma rays, which set constraints on some fundamental astrophysical models. We also use the data to investigate the validity of the new hadronic interactions models like SIBYLL version 2.3c or EPOS-LHC. In addition, we updated and improved the webbased platform of the KASCADE Cosmic Ray Data Centre (KCDC), where now the data from KASCADE and KASCADE-Grande of more than 20 years measurements is available, including corresponding Monte-Carlo simulated events based on three different hadronic interaction models. In this contribution, recent results from KASCADE-Grande and the update of KCDC is briefly discussed.

In this work, we report measurements on the muon content (Eth > 230 MeV) of extensive air showers (EAS) induced by cosmic rays with primary energy from 10 PeV up to 1 EeV performed with the KASCADE-Grande experiment. The measurements are confronted with SIBYLL 2.3. The results are focused on the dependence of the total muon number and the lateral density distribution of muons in EAS on the zenith angle and the total number of charged particles in the shower. We also present updated results of a detailed study of the attenuation length of shower muons, which reveal a deviation between the measured data and the predictions of the post-LHC hadronic interaction models SIBYLL 2.3, QGSJET-II-04 and EPOS-LHC.

Contains fulltext : 184360.pdf (Publisher’s version ) (Open Access)

The KASCADE-Grande observatory was a ground-based air shower array dedicated to study the energy and composition of cosmic rays in the energy interval E = 1 PeV –1 EeV. The experiment consisted of different detector systems which allowed the simultaneous measurement of distinct components of air showers (EAS), such as the muon content. In this contribution, we study the total muon number and the lateral density distribution of muons in EAS detected by KASCADE-Grande as a function of the zenith angle and the total number of charged particles. The attenuation length of the muon content of EAS is also measured. The results are compared with the predictions of the SIBYLL 2.3 high-energy hadronic interaction model.

The KASCADE-Grande large area (128 m2) Muon Tracking Detector has been built with the aim to identify muons ( E μ thr = 800 MeV) in Extensive Air Showers by track measurements under 18 r.l. shielding. This detector provides high-accuracy angular information (approx. 0.3 ° ) for muons up to 700 m distance from the shower core. In this work we present the lateral density distributions of muons in EAS measured with the Muon Tracking Detector of the KASCADE-Grande experiment. The density is calculated by counting muon tracks in a muon-to-shower-axis distance range from 100 m to 610 m from showers with reconstructed energy of 10 16 – 10 17 eV and zenith angle θ 18 ° . In the distance range covered by the experiment, these distributions are well described by functions phenomenologically determined already in the fifties (of the last century) by Greisen. They are compared also with the distributions obtained with the KASCADE scintillator array ( E μ thr = 230 MeV) and with distributions obtained using simulated showers.

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 gamma-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 gamma-rays to the total cosmic ray flux is obtained at $3.7 \times {10}^{15}$ eV with $1.1 \times {10}^{-5}$. Translated to an absolute gamma-ray flux this sets constraints on some fundamental astrophysical models, such as the distance of sources for at least one of the IceCube neutrino excess models., Published in The Astrophysical Journal, Volume 848, Number 1. Posted on: October 5, 2017

KASCADE and KASCADE-Grande were detector arrays for the measurement of extensive air showers generated by high-energy cosmic rays in the PeV to EeV energy range. KASCADE-Grande has been operated for more than two decades and completed the data taking at the end of 2013. Now, a new analysis of the combined data from the arrays of KASCADE and KASCADE-Grande was performed, increasing both the effective area and the accuracy of the shower reconstruction. In addition, new versions of post-LHC hadronic interaction models are used to interpret the combined data. First results from the new combined analysis confirming earlier observations of spectral features, but also unveiling still existing inconsistencies of the models, will be discussed in this contribution.

The KASCADE-Grande experiment has significantly contributed to the current knowledge about the energy spectrum and composition of cosmic rays for energies between the knee and the ankle. Meanwhile, post-LHC versions of the hadronic interaction models are available and used to interpret the entire data set of KASCADE-Grande. A new, combined analysis of both arrays, KASCADE and Grande, were developed increasing significantly the accuracy of the shower observables. Latest results from the analysis of the entire data set as well as recent activities related to scientific outreach of the KASCADE-Grande experiment are presented.

The KASCADE-Grande observatory was a ground-based air shower array devoted to the study of the energy and composition of cosmic rays with energies from $1$ PeV to $1$ EeV. The experiment consisted of different detector systems which allowed the simultaneous measurement of distinct components of the air showers (EAS), such as the muon content. In this contribution, we study the total muon number and the lateral density distribution of muons in EAS detected by KASCADE-Grande. The data are analyzed as a function of the zenith angle and the total number of charged particles. The attenuation length of the muon content of EAS is also measured. The results are compared with the predictions of the SIBYLL $2.3$ hadronic interaction model.

The KASCADE Cosmic Ray Data Centre (KCDC) is a web-based platform to provide scientific data for the general public. KASCADE and its extension KASCADE-Grande fully completed the data accumulation at the end of 2013 after more than 20 years of measurements. The main purpose of KCDC is to archive original data such as from KASCADE to offer long-term scientific data for the high-energy astroparticle physics community as well as for students and the interested public via a sophisticated web portal. Recently, a new version named NABOO was released, based on a completely new back-end database and software. In addition, the amount of data increased by factor 3 compared to the previous release. Data from the Grande detector array are now also available. In this contribution, the KCDC web portal and the data availability as well as future plans will be discussed.

The charged particle densities obtained from CORSIKA simulated EAS, using the QGSJet-II.04 hadronic interaction model are used for primary energy reconstruction. Simulated data are reconstructed by using Lateral Energy Correction Functions computed with a new realistic model of the Grande stations implemented in Geant4.10.

The KASCADE-Grande experiment operated at KIT from January 2004 to November 2012, measuring EAS generated by primary cosmic rays in the 10 16 –10 18 eV energy range. The experiment detected, for each single event, with a high resolution, the total number of charged particles ( N ch ) and of muons ( N μ ). In this contribution we present the latest results about: (i) The measurement of the all particle energy spectrum, discussing the influence of the hadronic interaction model used to derive the energy calibration of the experimental data. (ii) The energy spectra derived separating the events according to the N μ / N ch ratio. This technique allowed us to unveil a steepening of the spectrum of heavy primaries at E ~ 10 16.92 ± 0.04 eV and a hardening of the spectrum of light primaries at E ~ 10 17.08 ± 0.08 eV . (iii) The elemental spectra (for five mass groups) obtained applying a detailed unfolding analysis technique. (iv) A search for large scale anisotropies.

One of the main aims of the LOPES experiment was the evaluation of the absolute amplitudeof the radio signal of air showers. This is of special interest since the radio technique offers the pos-sibility for an independent and highly precise determination of the energy scale of cosmic rays onthe basis of signal predictions from Monte Carlo simulations. For the calibration of the amplitudemeasured by LOPES we used an external source. Previous comparisons of LOPES measurementsand simulations of the radio signal amplitude predicted by CoREAS revealed a discrepancy of theorder of a factor of two. A re-measurement of the reference calibration source, now performed forthe free field, was recently performed by the manufacturer. The updated calibration values leadto a lowering of the reconstructed electric field measured by LOPES by a factor of 2:6 0:2 andtherefore to a significantly better agreement with CoREAS simulations. We discuss the updatedcalibration and its impact on the LOPES analysis results.2

The energy reconstruction at KASCADE-Grande is based on a combination of the shower size and the total muon number, which are both estimated for each individual air shower event. We present investigations where we employed a second method to reconstruct the primary energy using S(500), which are the charged particle densities inferred with the KASCADE-Grande detector at a distance of 500 m from the shower axis. We considered the attenuation of inclined showers by applying the “Constant Intensity Cut” method and we employed a simulation-derived calibration to convert the recorded S(500) into primary energy. We observed a systematic shift in the S(500)-derived energy compared with previously reported results obtained using the standard reconstruction technique. However, a comparison of the two methods based on simulated and measured data showed that this shift only appeared in the measured data. Our investigations showed that this shift was caused mainly by the inadequate description of the shape of the lateral density distribution in the simulations.

Contains fulltext : 166007.pdf (Publisher’s version ) (Open Access) UHECR 2014 : International Symposium for Ultra-High Energy Cosmic Rays, October 12-15, 2014, Springdale, Utah, USA

Physics letters / B 763, 179 - 185(2016). doi:10.1016/j.physletb.2016.10.031, The radio technique is a promising method for detection of cosmic-ray air showers of energies around View the MathML source100PeV and higher with an array of radio antennas. Since the amplitude of the radio signal can be measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. We show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. Using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments Tunka-133 and KASCADE-Grande, using their radio extensions, Tunka-Rex and LOPES, respectively. Due to the consistent amplitude calibration for Tunka-Rex and LOPES achieved by using the same reference source, this comparison reaches an accuracy of approximately 10%10% – limited by some shortcomings of LOPES, which was a prototype experiment for the digital radio technique for air showers. In particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments KASCADE-Grande and Tunka-133 are consistent with each other on this level., Published by North-Holland Publ., Amsterdam

The KASCADE-Grande experiment operated at KIT from January 2004 to November 2012, measuring Extensive Air Showers (EAS) generated by primary cosmic rays in the 10 16 – 10 18 e V energy range. The experiment measured, for each single event, with a high resolution, the total number of charged particles ( N c h ) and of muons ( N μ ). In this contribution we summarize the results obtained about: (i) the measurement of the all particle energy spectrum, discussing the influence of the hadronic interaction model used to derive the energy calibration of the experimental data. (ii) The energy spectra derived separating the events according to the N μ / N c h ratio. This technique allowed us to unveil a steepening of the spectrum of heavy primaries at E ∼ 10 16.92 ± 0.04 e V and a hardening of the spectrum of light primaries at E ∼ 10 17.08 ± 0.08 e V . (ii) A search for large scale anisotropies.

LOPES was a digital antenna array operating for approximately 10 years until spring 2013 at the Karlsruhe Institute of Technology (KIT). Triggered by the co-located KASCADE-Grande air-shower experiment, it measured the radio signal of around 1000 cosmic-ray air showers with energies E ≳ 1017 eV in an effective band of 43 - 74 MHz. Using the interferometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy < 0.7°, the shower energy with a precision < 20%, and the atmospheric depth of the shower maximum, Xmax, with a precision < 95g/cm2. In particular the reconstruction of the shower maximum suffers from significant measurement uncertainties due to the radio-loud environment of the site. This article summarizes our latest results on the reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impact of the lessons learned at LOPES for future antenna arrays.

The KASCADE experiment and its extension KASCADE-Grande have significantly contributed to the current knowledge about the energy spectrum and composition of cosmic rays (CRs) with energies between the knee and the ankle. However, the data of both experiments were analysed separately, although Grande used the muon information of the KASCADE-array. A coherent analysis based on the combined data of both arrays is expected to profit from reconstructed shower observables with even higher accuracy compared to the stand-alone analyses. In addition, a significantly larger fiducial area is available. The aim of this analysis is to obtain the spectrum and composition of CRs in the range from 1014 to 1018 eV with a larger number of events and further reduced uncertainties using one unique reconstruction procedure for the entire energy range. This contribution will describe the motivation, the concept, and the current status of the combined analysis.

KCDC, the KASCADE Cosmic-ray Data Centre, is a web portal, where data of astroparticle physics experiments will be made available for the interested public. The KASCADE experiment, financed by public money, was a large-area detector for the measurement of high-energy cosmic rays via the detection of air showers. KASCADE and its extension KASCADE-Grande stopped finally the active data acquisition of all its components including the radio EAS experiment LOPES end of 2012 after more than 20 years of data taking. In a first release, with KCDC we provide to the public the measured and reconstructed parameters of more than 160 million air showers. In addition, KCDC provides the conceptional design, how the data can be treated and processed so that they are also usable outside the community of experts in the research field. Detailed educational examples make a use also possible for high-school students and early stage researchers., Comment: 8 pages, accepted proceeding of the ECRS-symposium, Kiel, 2014

In previous studies of KASCADE-Grande data, a Monte Carlo simulation code based on the GEANT3 program has been developed to describe the energy deposited by EAS particles in the detector stations. In an attempt to decrease the simulation time and ensure compatibility with the geometry description in standard KASCADE-Grande analysis software, several structural elements have been neglected in the implementation of the Grande station geometry. To improve the agreement between experimental and simulated data, a more accurate simulation of the response of the KASCADE-Grande detector is necessary. A new simulation code has been developed based on the GEANT4 program, including a realistic geometry of the detector station with structural elements that have not been considered in previous studies. The new code is used to study the influence of a realistic detector geometry on the energy deposited in the Grande detector stations by particles from EAS events simulated by CORSIKA. Lateral Energy Correction Functions are determined and compared with previous results based on GEANT3.

KASCADE-Grande was an air-shower experiment designed to study cosmic rays between 1016 and 1018 eV. The instrument was located at the site of the Karlsruhe Institute of Technology, Germany at an altitude of 110 m a.s.l. and covered an area of 0.5 km2. KASCADE-Grande consisted of several detector systems dedicated to measure different components of the EAS generated by the primary cosmic rays, i.e., the muon and the electron contents of the air-shower. With such a number of EAS observables and the precision of the measurements, the KASCADE-Grande data can be used to not only study in detail the properties of cosmic rays but also to test the predictions of hadronic-interaction models. In this work, in particular, the attenuation lengths of the muon number and the charged number of particles of EAS in the atmosphere were extracted from the KASCADE-Grande data and the results were compared with the predictions of the new EPOS-LHC hadronic-interaction model.

The shape and composition of the primary spectrum of cosmic rays are key elements to understand the origin, acceleration and propagation of the Galactic cosmic rays. Besides the well known knee and ankle features, the recent results of KASCADE-Grande indicate that the measured energy spectrum exhibits also a less pronounced but still clear deviation from a single power law between the knee and the ankle, with a spectral hardening at 2 × 1016 eV and a steepening at 1017 eV. The average mass composition gets heavier after the knee till 1017 eV where a bending of the heavy component is observed. An indication of a hardening of the light component just above 1017 eV has been measured as well. In this paper the major results obtained so far by the KASCADE-Grande experiment are reviewed.

Previous results obtained by KASCADE-Grande using the QGSjetII-02 hadronic interaction model have shown that the energy spectrum of cosmic rays between 10 16 eV and 10 18 eV exhibits a significant hardening at approximately 2 × 10 16 eV and a slight but statistically significant steepening close to 10 17 eV. Moreover, the analysis with QGSjetII-02 suggests that the break observed around 10 17 eV is caused by the heavy component of primary cosmic rays. In this paper, we report on the results of similar analyses performed using the SIBYLL 2.1 and EPOS 1.99 hadronic interaction models to interpret the data. The present results confirm qualitatively the previous findings. However, the intensity of the all-particle spectrum, the positions of the hardening and steepening of the spectrum, as well as the relative abundance of the heavy and light mass groups depend on the hadronic interaction model used to interpret the data.

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 $45^\circ$, 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 $\gtrsim 50\,$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, $X_\mathrm{max}$, 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., Comment: accepted by JCAP

Recent results of the KASCADE-Grande experiment provided evidence for a mild knee-like structure in the all-particle spectrum of cosmic rays at $E = 10^{16.92 \pm 0.10} \, \mathrm{eV}$, 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 $10^{16.3} \, \mathrm{eV}$ to $10^{18} \, \mathrm{eV}$. 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 measurements 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 $E = 10^{17.08 \pm 0.08} \, \mathrm{eV}$ with a change of the power law index from $-3.25 \pm 0.05$ to $-2.79 \pm 0.08$., 6 pages, 5 figures, 1 table; this is the authors' version; the definite version has been published in Phys. Rev. D (http://link.aps.org/doi/10.1103/PhysRevD.87.081101)

The KASCADE-Grande air shower experiment [W. Apel, et al. (KASCADE-Grande collaboration), Nucl. Instrum. Methods A 620 (2010) 202] consists of, among others, a large scintillator array for measurements of charged particles, Nch, and of an array of shielded scintillation counters used for muon counting, Nmu. 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 [T. Antoni, et al. (KASCADE collaboration), Astropart. Phys. 24 (2005) 1], we have now extended these measurements to beyond 200 PeV. By analysing the two-dimensional shower size spectrum Nch vs. Nmu 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 [W. Apel, et al. (KASCADE-Grande collaboration), Phys. Rev. Lett. 107 (2011) 171104]., Accepted for publication in Astropart. Phys. (2013)

KASCADE-Grande is dedicated for investigations of cosmic-ray air showers in the primary energy range from 10 PeV to 1 EeV. The multi-detector system allows us to reconstruct charged particles, electron and muon numbers for individual air showers with high accuracies. Based on the shower size ($N_{ch}$) spectra of the charged particle component, the all-particle energy spectrum of cosmic rays is reconstructed, where attenuation effects in the atmosphere are corrected by applying the constant intensity cut method. The energy calibration is performed by using CORSIKA simulations with high-energy interaction models QGSJET-II-2, QGSJET-II-4, EPOS 1.99 and SIBYLL 2.1, where FLUKA has been used as low-energy interaction model for all cases. In the different hadronic models, different abundances for shower particles are predicted. Such model differences in the observables will be compared and discussed in this contribution. Furthermore, by using data with increasing statistics, the updated energy spectra by means of different interaction models will be presented.

The detection of high-energy cosmic rays above a few hundred TeV is realized by the observation of extensive air-showers. By using the multi-detector setup of KASCADE-Grande, and here in particular the detectors of the large Grande array, the energy spectrum and the elemental composition of high-energy cosmic rays in the energy range from 10 PeV to 1 EeV are investigated. The estimation of energy and mass of the high-energy primary particles is based on the combined analysis of the total number of charged particles and the total number of muons measured by the detector arrays of Grande and KASCADE, respectively. The latest analysis results have shown that in the all-particle spectrum two features are present: a hardening of the spectrum at energies around 20 PeV and a steepening, i.e. a knee-like structure, at 80-90 PeV. The latter one was found to be due to a decrease of flux of the heavy mass component.

KASCADE-Grande is an air-shower observatory devoted to the study of cosmic rays with energies in the range 1016 – 1018 eV. In KASCADE-Grande, different detector systems allow independent measurements of the number of muons (Nμ) and charged particles (Nch) of air showers, which are the basis for several energy and composition studies of cosmic rays. In this contribution, a composition analysis using the shower size ratio lgNμ/lgNch, corrected for attenuation in the atmosphere, is described. Using QGSJET II-based simulations of different primaries, it is shown that an energy independent cut on the shower ratio can be chosen in order to separate the cosmic ray events into light and heavy mass groups. The analysis is applied to the KASCADE-Grande data. The energy spectra derived from the analysis are presented.

With the KASCADE-Grande Muon Tracking Detector it was possible to measure with high accuracy directions of EAS muons with energy above 0.8 GeV and up to 700 m distance from the shower centre. Reconstructed muon tracks allow investigation of muon pseudorapidity (η) distributions. These distributions are nearly identical to the pseudorapidity distributions of their parent mesons produced in hadronic interactions. Comparison of the η distributions from measured and simulated showers can be used to test the quality of the high energy hadronic interaction models. The pseudorapidity distributions reflect the longitudinal development of EAS and, as such, are sensitive to the mass of the cosmic ray primary particles. With various parameters of the η distribution, obtained from the Muon Tracking Detector data, it is possible to calculate the average logarithm of mass of the primary cosmic ray particles. The results of the < ln A > analysis in the primary energy range 1016 eV-1017 eV with the 1st quartile and the mean value of the distributions will be presented for the QGSJet-II-2, QGSJet-II-4, EPOS 1.99 and EPOS LHC models in combination with the FLUKA model.

We report the first direct measurement of the overall characteristics of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the CROME (Cosmic-Ray Observation via Microwave Emission) experiment have been read out and searched for signatures of radio emission by high-energy air showers in the GHz frequency range. Microwave signals have been detected for more than 30 showers with energies above 3*10^16 eV. The observations presented in this Letter are consistent with a mainly forward-directed and polarised emission process in the GHz frequency range. The measurements show that microwave radiation offers a new means of studying air showers at energies above 10^17 eV., Accepted for publication in PRL

LOPES was a digital antenna array detecting the radio emission of cosmic-ray air showers. The calibration of the absolute amplitude scale of the measurements was done using an external, commercial reference source, which emits a frequency comb with defined amplitudes. Recently, we obtained improved reference values by the manufacturer of the reference source, which significantly changed the absolute calibration of LOPES. We reanalyzed previously published LOPES measurements, studying the impact of the changed calibration. The main effect is an overall decrease of the LOPES amplitude scale by a factor of $2.6 \pm 0.2$, affecting all previously published values for measurements of the electric-field strength. This results in a major change in the conclusion of the paper 'Comparing LOPES measurements of air-shower radio emission with REAS 3.11 and CoREAS simulations' published in Astroparticle Physics 50-52 (2013) 76-91: With the revised calibration, LOPES measurements now are compatible with CoREAS simulations, but in tension with REAS 3.11 simulations. Since CoREAS is the latest version of the simulation code incorporating the current state of knowledge on the radio emission of air showers, this new result indicates that the absolute amplitude prediction of current simulations now is in agreement with experimental data., Comment: Partly changes results and conclusion of publication Astroparticle Physics 50-52 (2013) 76-91 (arXiv:1309.5920)