Cross Section and composition of UHECR at the Pierre Auger Observatory and Risetime at 1000 m distributions

JARNE, CECILIA; WAHLBERG HERNÁN, DOVA MARÍA TERESA

Paris

Otro; ISAPP: International School of Astroparticle Physics; 2012

We have performed studies towards the determination of he primary mass composition of Ultra High Energy Cosmic Rays (UHECR) with the Pierre Auger Observatory. Particle showers induced by different primary species will contain different number of particles at ground. Of special interest is the relation between electrons and muons, where heavy particles such as Iron have a stronger muon component than lighter nuclei. The time distribution of the secondary particles of the shower front reaching the ground detectors is a variable sensitive to muon and electron ratio, in particular the time in which the signal in the detectors rise to half of the total integrated signal (rise time). The risetime at 1000 mts from the shower axis, obtained on event by event basis, is a robust variable to build different observables with the aim of inferring mass composition and cross sections of UHECR.