Estimation of the chemical composition in the 'knee' region from the muon/electron ratio in EAS

New data on the muon/electron ratio derived from the KASCADE extensive air shower experiment are presented. This ratio is known to be the most sensitive parameter in the determination of the mass of the primary particle when using ground array data. The particle numbers are measured with the KASCADE array comprising 500 m 2 of e/γ- and 620 m 2 of μ - detectors. The primary mass is inferred on an event-by-event basis by comparing the experimental data to corresponding EAS simulations. We observe a change towards a heavier composition with increasing energy above the knee. The sensitivity of this result to the specific hadronic interaction model employed in the simulations (e.g. VENUS and QGSJET) is discussed.