To investigate the impact of uncertainties in the knowledge of properties of individual hadronic interactions on the development of extensive air showers, the inelastic proton-proton cross section and the elasticity of interactions have been modified within the interaction model QGSJET. Air shower simulations are performed using the CORSIKA code. The influence of the modifications on observables like the number of electrons, muons, and hadrons registered at ground level are investigated. The predictions are compared to measurements of the KASCADE experiment.

We present the design and first test results of a new FADC-based data acquisition (DAQ) system for the Grande array of the KASCADE-Grande experiment. The original KASCADE experiment at the Forschungszentrum Karlsruhe, Germany, has been extended by 37 detector stations of the former EAS-TOP experiment (Grande array) to provide sensitivity to energies for primary particles from the cosmos up to 10/sup 18/ eV. The new FADC-based DAQ system will improve the quality of the data taken by the Grande array by digitizing the scintillator signals with a 250 MHz sampling rate. The signals of each of the 37 detector stations are continuously recorded using cascaded 12-bit flash analog-to-digital-converters (FADCs) located on custom made digitizer boards at each station. The digitizer boards feature a self-triggering mechanism, initiating the data transmission to the Grande DAQ station using programmable thresholds, a time stamp mechanism and optical data transmission. The control logic is implemented using field programmable gate arrays (FPGAs). Five optical receiver and temporary storage modules receive the data from up to eight stations each (at an approximate rate of 2.5 MB/s per station) and transfer them into the memory of one of five PCs via a customized PCI interface card. Running on a master PC, the data acquisition software searches for coincidences in the time stamps, incorporates triggers generated by the other KASCADE-Grande components and builds air shower events from the data of the individual stations. Completed Grande events will be sent to the central DAQ of KASCADE-Grande at an approximate rate of a few air shower events per second. Two Grande stations have been equipped with the FADC-based data acquisition system this summer (2004) and first data are shown. By the beginning of 2005 completion of the full system is anticipated.

Directional information on air showers from the KASCADE Array and on muons registered in the Muon Tracking Detector (MTD) allow to investigate pseudorapidity and momentum distributions of muons. The possibility to test hadronic interaction models, to study primary mass composition and parameters of hadronic interactions with these distributions is discussed.

KASCADE is a multi-detector setup to get redundant information on single air shower basis. The information is used to perform multiparameter analyses to solve the threefold problem of the reconstruction of (i) the unknown primary energy, (ii) the primary mass, and (iii) to quantify the characteristics of the hadronic interactions in the air-shower development. In this talk recent results of the KASCADE data analyses are summarized concerning cosmic ray anisotropy studies, determination of flux spectra for different primary mass groups, and approaches to test hadronic interaction models. Neither large scale anisotropies nor point sources were found in the KASCADE data set. The energy spectra of the light element groups result in a knee-like bending and a steepening above the knee. The topology of the individual knee positions shows a dependency on the primary particle. Though no hadronic interaction model is fully able to describe the multi-parameter data of KASCADE consistently, the more recent models or improved versions of older models reproduce the data better than few years ago.

Recent results of the KASCADE air shower experiment are presented, in order to shed some light on the astrophysics of cosmic rays in the region of the knee in the energy spectrum. The results include investigations of high-energy interactions in the atmosphere, the analysis of the arrival directions of cosmic rays, the determination of the mean logarithmic mass, and the unfolding of energy spectra for elemental groups.

Occasionally cosmic-ray induced air showers result in single, unaccompanied hadrons at ground level. Such events are investigated with the 300m(2) hadron calorimeter of the KASCADE-Grande experiment. It is an iron sampling calorimeter with a depth of 11 hadronic interaction lengths read out by warm-liquid ionization charnbers. The longitudinal shower development is discussed as function of energy tip to 30 TeV and the results are compared with simulations using the GEANT/FLUKA code. In addition, results of test measurements at a secondary particle beam of the Super Proton Synchrotron at CERN up to 350 GeV are discussed.

We present the results of an analysis of the large-scale anisotropy of cosmic rays in the PeV range. The Rayleigh formalism is applied to the right ascension distribution of extensive air showers measured by the KASCADE (Karlsruhe Shower Core and Array Detector) experiment. The data set contains about 108 extensive air showers in the energy range 0.7-6 PeV. No hints of anisotropy are visible in the right ascension distributions in this energy range. This accounts for all showers, as well as for subsets containing showers induced by predominantly light or heavy primary particles, respectively. Upper flux limits for Rayleigh amplitudes are determined to be between 10-3 at a primary energy of 0.7 PeV and 10-2 at 6 PeV.

Radio pulses emitted in the atmosphere during the air shower development of high-energy primary cosmic rays were measured during the late 1960ies in the frequency range from 2 MHz to 520 MHz. Mainly due to difficulties with radio interference these measurements ceased in the late 1970ies. LOFAR (Low Frequency Array) is a new digital radio interferometer under development. Using high bandwidth ADCs and fast data processing it will be able to filter out most of the interference. By storing the whole waveform information in digital form one can analyze transient events like air showers even after they have been recorded. To test this new technology and to demonstrate its ability to measure air showers a ”LOFAR Prototype Station” (LOPES) is set up to operate in conjunction with an existing air shower array (KASCADE-Grande). The first phase consisting of 10 antennas is already running. It operates in the frequency range of 40 to 80 MHz, using simple short dipole antennas and direct 2nd Nyquist sampling of the incoming wave. It has proven to be able to do simple astronomical measurements, like imaging of a solar burst. It has also demonstrated how digital interference suppression and beamforming can overcome the problem of radio interference and pick out air shower events.

The flux of cosmic-ray-induced single hadrons near sea level has been measured with the large hadron calorimeter of the KASCADE experiment. The measurement corroborates former results obtained with detectors of smaller size if the enlarged veto of the 304 m2 calorimeter surface is accounted for. The program CORSIKA/QGSJET is used to compute the cosmic-ray flux above the atmosphere. Between E0 = 300 GeV and 1 PeV the primary proton spectrum can be described with a power law parameterized as dJ/dE0 = (0.15 ± 0.03)E m-2 s-1 sr-1 TeV-1. At the lower energy end the proton flux compares well with the results from recent direct measurements.

Recent results from the KASCADE experiment on measurements of cosmic rays in the energy range of the knee are presented. Emphasis is placed on energy spectra of individual mass groups as obtained from an two-dimensional unfolding applied to the reconstructed electron and truncated muon numbers of each individual EAS. The data show a knee-like structure in the energy spectra of light primaries (p, He, C) and an increasing dominance of heavy ones (A greater than or similar to 20) towards higher energies. This basic result is robust against uncertainties of the applied interaction models QGSJET and SIBYLL which are used in the shower simulations to analyse the data. Slight differences observed between experimental data and EAS simulations provide important clues for further improvements of the interaction models. The data are complemented by new limits on global anisotropies in the arrival directions of CRs and by upper limits on point sources. Astrophysical implications for discriminating models of maximum acceleration energy vs galactic diffusion/drift models of the knee are discussed based on this data.

A survey of the northern hemisphere for astrophysical point sources with continuous emission of high-energy cosmic rays is presented. Around 4.7 × 107 extensive air showers with primary energies above ≈300 TeV measured by the KASCADE detector field are selected for this analysis. Besides the sky survey, a search for signal excess in the regions of the Galactic plane and of selected point-source candidates has been performed. There is no evidence for any significant excess. This is valid for an analysis of all recorded showers, as well as for a data set enhanced by γ-ray-induced showers. An upper flux limit of around 3 × 10-10 m-2 s-1 for a steady point source that transits the zenith is obtained. Additionally, the distribution of the arrival directions of extensive air showers with energies above 80 PeV was studied by an autocorrelation analysis.

The main aim of the KASCADE experiment is the determination of the primary energy spectrum and chemical composition of cosmic rays through the measurement of extensive air showers at energies around 4 . 10(15) eV, the so called knee region. An overview over the measurement and reconstruction procedures of the large field array is presented.

KASCADE (KArlsruhe Shower Core and Array DEtector) is determining flux spectra for different primary mass groups to disentangle the knee feature of the primary cosmic-ray energy spectrum. The energy spectra of the light element groups result in a knee-like bending and a steepening above the knee. The topology of the individual knee positions suggests a rigidity dependence. To proof the rigidity dependence the KASCADE array is now extended by a factor 10 in area. The major goal of KASCADE-Grande is the observation of the ’iron-knee’ in the cosmic-ray spectrum at around 100 PeV which is expected following the KASCADE observations.

Recent results from the KASCADE experiment on measurements of cosmic rays in the energy range of the knee are presented. Emphasis is placed on energy spectra of individual mass groups as obtained from sophisticated unfolding procedures applied to the reconstructed electron and truncated muon numbers of EAS. The data clearly show a knee in the energy spectra of the light primaries (p, He, C) and an increasing dominance of heavy ones (A > 20) toward higher energies. This basic result is robust against uncertainties of the applied interaction models QGSJET and SIBYLL. Slight differences observed between experimental data and EAS simulations provide important clues for improvements of the interaction models. Astrophysical implications for discriminating models of maximum acceleration energy vs galactic diffusion/drift models of the knee will be discussed. To improve the reconstruction quality and statistics around 10(17) eV, KASCADE has recently been extended by a factor 10 in area. The status and expected performance of the new experiment KASCADE-Grande is discussed.

We describe the main features of the extensive air-shower array devoted to the study of cosmic-ray primaries and their interactions at primary energies 10PeV–1EeV which is starting operation at Forschungszentrum Karlsruhe. It exploits the existing KASCADE multi-detector facilities, and two new detectors: Grande and Piccolo, with the respective aims of providing a large acceptance area (0.5km2) and a prompt trigger signal.

The energy spectrum of unaccompanied hadrons is measured with the large hadron calorimeter of the KASCADE experiment. From the measured flux at detector level the primary proton spectrum at the top of the atmosphere has been derived. The flux obtained is well compatible with results of direct measurements.

KASCADE-Grande extends the former KASCADE experiment by a large area scintillator array (0.5 km(2)) for the detection of the charged component of extensive air showers. Its goal is to reconstruct the primary energy and composition of cosmic rays up to energies of 10(18) eV thereby allowing a detailed investigation of the expected iron-knee. Knowing the shower core and size as well as its direction from the Grande array the KASCADE detectors allow the determination of the muon number above different energy thresholds. We present the accuracy of the shower reconstruction methods based on CORSIKA simulations. Implications to the discrimination power of the obtained parameters with respect to the nature of the primary particles will be considered.

Using the facilities of the KASCADE Central Detector EAS muon arrival time distributions, observed with reference to the arrival time of the first locally registered muon, and their correlations with other EAS observables have been investigated at different distances Rμ from the shower axis. Invoking detailed Monte Carlo simulations non-parametric multivariate even-by-event analyses have been performed for an estimate of the primary mass composition. The consistency of the Monte Carlo simulations is studied by comparing the primary mass composition results inferred from observations at different Rμ and different muon multiplicity thresholds nth.

Muon production heights in EAS provide a specific tool to investigate the longitudinal development of EAS, since muons are little affected by subsequent interactions in the atmosphere. Multiplicity of muons presents also a unique tool to investigate hadronic interaction models. The capability of the Muon Tracking Detector to measure radial and tangential angles of muon tracks in EAS, in combination with the shower direction determined by the Array of the KASCADE experiment, has been investigated. Due to different characteristics in shower development of light and heavy primary cosmic ray particles the radial angle and therefore the related production height is sensitive to the mass of them. Muon production height (MPH) and muon production depth (MPD) were studied in different bins of the muon shower size for measured data and MC simulations, which have been performed using the Monte Carlo program CORSIKA with the hadronic interaction models QGSJet and NEXUS. First composition studies on the basis of MPD distributions have been carried out.

The KASCADE experiment measures a high number of EAS observables with a large degree of sampling of the electron-photon, muon, and hadron components. It provides accurate data for an event-by-event analysis of the primary cosmic ray flux in the energy range around the knee. The possibility of selecting samples of enriched proton and iron induced extensive air showers by applying the statistical techniques of multivariate analyses is scrutinized using detailed Monte Carlo simulations of three different primaries. The purity and efficiency of the proton and iron classified events is investigated. After obtaining enriched samples from the measured data by application of the procedures the reconstructed number of hadrons, hadronic energy and other parameters are investigated in the primary energy range 1-10 PeV. By comparing these shower parameters for purified proton and iron events, respectively, with simulated distributions an attempt is made to check the validity of strong interaction models at high energies.