Grant number: 13/26444-2 Support type: Scholarships in Brazil - Post-Doctorate Effective date (Start): May 01, 2014 Effective date (End): March 31, 2016 Field of knowledge: Physical Sciences and Mathematics - Physics - Elementary Particle Physics and Fields Principal Investigator: Carola Dobrigkeit Chinellato Grantee: Eva Maria Martins dos Santos Home Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil Associated research grant: 10/07359-6 - Study of cosmic rays of highest energies with the Pierre Auger Observatory , AP.TEM Abstract The Pierre Auger Observatory is the World's largest detector of cosmic rays with energies between $10^{17.5}\:\mathrm{eV}$ and $10^{20}\:\mathrm{eV}$. Composed of a surface detector, formed by an array of 1660 \u{C}erenkov water detectors arranged on an area of $3000\:mathrm{km^{2}}$, and 5 fluorescence detectors, the Pierre Auger Observatory has among its main objectives, to determine the origin and nature of these cosmic rays with unprecedented statistics. In the energy region of interest, cosmic rays are detected indirectly through the many millions of particles that are produced in a cascade process - called Extensive Air Shower resulting from their interaction in the atmosphere. Among the most recent results published by the Pierre Auger Observatory is the determination of the chemical composition of cosmic rays with energies $E > 10^{18}\:\mathrm{eV}$. From these results, it is observed that as the energy increases, the average chemical composition of cosmic rays evolves from a population mainly dominated by the lightest elements of the periodic table, to a heavier one. There are several variables that are sensitive to the chemical composition of cosmic rays. Among them is the measurement of the muonic component of the shower and, in particular, the measurement of the profile of the muons produced as a function of the atmospheric depth. In this project, the measurements made by the surface detector of the Pierre Auger Observatory of the muonic component of the shower will be used to determine, in an independent way, the nature of cosmic rays. The study will also address the potentialities and the performance of the muon measurements of the detectors which will be installed after 2015 in the Pierre Auger Observatory. (AU)