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Since its start-up early 1996 KASCADE has collected more than 200 Mio. events with an energy threshold of approx. 10 eV. A unique feature of KASCADE is the simultaneous measurement of electrons, muons, and hadrons at high quality. The large body of data can consistently be described only, if an increasingly heavier composition is assumed above the knee. Quantitatively, subtle differences are identified between hadronic and electromagnetic measurements, with the former pointing to an overall heavier composition. The knee in the primary energy spectrum is observed at E k = 4-5 PeV with a change of the spectral index from fl ' 2:7 to 3.1. We critically discuss the preliminary results and point out possible future improvements, particularly in the modeling of EAS

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The electron and muon numbers of extensive air showers in the energy region around the knee are measured by the detectors of the KASCADE array. To understand the resulting size spectra one has to take into account the fluctuations of the shower development in the atmosphere as well as the uncertainties of the applied reconstruction methods. A consistent interpretation of both spectra allows to derive a primary energy spectrum and a mass composition

HE 2.2.04 1 Estimation of the Energy Spectrum in the Knee Region by the

The KASCADE experiment measuring a larger number of EAS observables with an improved sampling of the electron-photon, hadron, and muon components than previous experiments, provides data accurate enough for an event-by-event analysis of the energy dependence of the primary cosmic ray flux in the energy range of 10 \Gamma 10 eV. Multivariate statistical analysis approaches enable to estimate the primary cosmic ray flux and the elemental composition. The major feature in the observed PeV energy region, the so called knee is reproduced, spectral indices and the knee energy are determined

He 2.2.41 1

The number of hadrons and their energy sum in extensive air showers has been measured using the KASCADE hadron calorimeter. Shower size spectra of the hadronic component have been derived using both observables. The spectra can be described by a power law and exhibit a change in the spectral index at energies around 5 PeV. The primary cosmic--ray flux spectrum is derived from the measurements in the energy range from 0.2 PeV up to 50 PeV

HE 2.2.40 1 A Multivariate Approach for the Determination of the Mass

New results of a multivariate analysis to determine the chemical composition obtained with the KASCADE detector are presented. Taking the information of the electron-photon, the hadron, and the muon detectors for an event-by-event analysis into account the energy dependence of the primary cosmic ray composition in the knee region is estimated. Bayesian nonparametric and neural network methods are used. The investigated EAS events indicate a tendency to a heavier composition above the knee

HE 1.3.02 1 Precision Test of Hadronic Interaction Models

Extrapolations of hadronic interaction models into kinematical and energy regions beyond the limit of accelerator data may heavily influence the interpretation of EAS data, especially the estimation of primary energy spectra and mass composition. In order to test and possibly improve the model predictions, the muon trigger and hadron rate observed with the KASCADE central detector are analysed and compared to CORSIKA simulations. The hadrons detected result from primary particles in the energy range of 0.1 to 500 TeV. Taking the measured particle fluxes from direct observations, we find fewer hadrons than predicted. Adopting a slightly larger total cross-section for pp interactions, such as suggested by findings of the CDF experiment at Fermilab, a noticeable improvement but still unsatisfactory description is obtained. Investigations to further improve the predictions are under way; the physical implications of the results are discussed

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It is shown how to determine fluctuations of the muon density in EAS at a given distance from the core, for showers with a fixed size. The method does not make use of any pre-assumed lateral muon distribution and uses only information whether muon detector has been hit by at least one muon

HE 2.2.38 1 Studies of the relative arrival time distributions of the

Arrival time distributions of EAS muons and their differences from the arrival times of the electronmagnetic component, has been measured with the timing facilities of the central detector of the KASCADE experiment. The results have been analysed in terms of CORSIKA Monte-Carlo simulations of the EAS development, based on the QGSJET model