Muon arrival time distributions and its relationship to the mass composition of ultra high energy cosmic raysan application to the Pierre Auger observatory

Abstract

This Ph.D. Thesis is devoted to the search and optimization of a new mass composition sensitive parameter measured with the Surface Detector of the Pierre Auger Observatory. It has been shown that it is possible to reconstruct the Muon Production Distance distributions (MPD). This is accomplished using the FADCs of the tanks far from the core of the shower measured at ground. These distributions provide information about the longitudinal development of the hadronic shower in an indirect way. We de ne our new mass sensitive parameter, Xmumax, as the point along the shower axis where the number of produced muons is maximal (i.e., the MPD maximum). This new observable is, in some sense, similar to Xmax, but it is related to the hadronic development of the shower instead of the electromagnetic one. The goal of this Ph.D work is to obtain an alternative Elongation Rate (ER) with our new variable, absolutely independent of Xmax and FD data, for the highest energy region of cosmic rays (log10(E/eV) > 19.0).