2016: Florian Gaté
More than a century after their discovery, cosmic-rays are still puzzling physicists. The flux of these particles coming from extraterrestrial sources strongly decreases as a function of their energy. Above 1 PeV (10¹⁵ eV), the particle flux becomes too low to allow a direct detection on a reasonable time scale. However, the cascades of secondary particles produced after the interaction of cosmic-rays with the constituents of the atmosphere are detectable at the ground level; it is the indirect detection. Above 100 PeV, the number of observations is too low to accurately estimate the mass of the cosmic rays and then to constrain the prediction models of acceleration mechanisms, propagation and type of sources. The determination of their composition is achieved at the Pierre Auger Observatory using fluorescence telescopes from the measurement of the Xmax observable with a duty cycle of 14Online access to his document (Thèses en ligne)