Cosmic Ray Composition in the 'Knee' Region Deduced from the Lateral Distribution of Cerenkov Light Emitted in Extensive Air Showers

We report the first result of measurements of the lateral distribution of Cerenkov light associated with cosmic ray extensive air showers with size between 105.0 and 106.6 observed in the Liangwang Mountain Observatory, 90 km east of Kunming City in China. The change trend towards heavy nucleus dominance of the primary cosmic ray composition in the `knee' region is deduced with the aid of a Monte Carlo simulation.