Cosmic-Ray Positron Fraction Measurement with the AMS-02 Detector

The study of Cosmic-Rays has proved to be of utmost importance in the understanding of the processes that govern our galaxy and has became a privileged field for the discovery of new physics. The current availability of precision measurements in a number of recent experiments such as PAMELA or Fermi, and in particular AMS-02, has provided a unique opportunity to challenge the theoretical framework that builds our comprehension of Nature. Certainly, the recent advent of new data on Cosmic-Ray electrons and positrons has raised disagreements with our current knowledge of production and propagation of Cosmic-Rays. The observation of an excess in the Cosmic-Ray electron spectrum has triggered enormous efforts to understand the origin of this anomaly, both from the theoretical and experimental points of view. In this context, AMS is a long awaited program, that among other objectives, will provide the most accurate measurement of the Cosmic-Ray electron spectrum, making possible to investigate a fundamental open question in particle astrophysics: the physical nature of the Dark Matter content of our galaxy. The aim of this thesis is to contribute towards this direction from two complementary perspectives: • From a purely phenomenological point of view, a method to discriminate an exotic contribution to the Cosmic-Ray electron spectrum from an astrophysical one is presented. • A detailed analysis of the positron fraction with the AMS-02 detector has been carried out, providing the most precise measurement to date in the energy range of 2-350 GeV. Finally, the ideas presented in the first part of this work are used to inspect the AMS-02 positron fraction measurement.