A Monte Carlo exploration of methods to determine the UHECR composition with the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION (AUTOR 434 DE 474); M. TUEROS

Lodz, Polonia

Conferencia; 31st International Cosmic Ray Conference; 2009

Measuring the mass composition of ultra high energy comsic rays is crucial for understanding their origin. In this paper, we present three statistical methods for determining the mass composition. Themethods compare observables measured with the Pierre Auger Observatory with corresponding Monte Carlo predictions for different mass groups obtained using different hadronic interaction models. Thetechniques make use of the mean and fluctuations of Xmax , the log-likelihood fit of the Xmax distributions and the multi-topological analysis of a selection of parameters describing the shower profile. Weshow their sensitivity to the input composition of simulated samples of known mixing and their ability to reproduce mass sensitive observables, like the average shower maximum as a function of the energy,measured at the Pierre Auger Observatory.