Mass composition studies using the surface detector of the Pierre Auger Observatory.

H. WAHLBERG FOR THE HERAB COLLABORATION

Paris

Simposio; 15th International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2008); 2008

The mass composition of ultra-high energy cosmic rays is a critical issue to understand their origin and nature. The Pierre Auger Observatory is a hybrid instrument which provides a powerful environment for the determination of the primary mass. The Surface Detector of the Pierre Auger Observatory alone allows the study of several shower parameters with high discriminating power between primary elements. Novel analysis techniques using different features of signals in the Cherenkov stations are discussed. These are the signal risetime, the azimuthal time asymmetry and the muon density of the showers.