The dual imaging cerenkov experiment (DICE) and the elemental composition in the “Knee” region

Abstract

An outstanding problem in cosmic ray physics is the cosmic ray elemental abundance in the “knee” region of the charged particle spectrum. The Dual Imaging Cerenkov Experiment (DICE) is designed to measure the mean elemental mass and energy spectrum around the “knee” energy by using composition sensitive properties of Extensive Air Showers (EAS). We present preliminary results on one EAS parameter, the average depth of shower maximum, 〈 X max 〉. We also show evidence for a change in the cosmic ray spectral index, a result which is in qualitative agreement with other experiments. A small increase in 〈 X max 〉 is present at the onset of the “knee”, implying an increase in the relative number of lighter elements. Further consistency tests of these results which are in progress are described.