Medida de la anisotropía a gran escala en electrones, positrones y protones cósmicos con el detector AMS-02 en la ISS

Resumen

In the last years, Cosmic Ray Physics has profited from the rise in space research, and space-based experiments are currently providing direct measurements with unprecedent precision. In this context, recent measurements of the spectra of several cosmic ray species cannot be fully explained within the current paradigm of cosmic ray origin and propagation, and constitute an open window into new fundamental physics phenomena. In particular, the precise measurements provided by AMS-02 allow to characterize the so-called positron excess, non-consistent with the standard secondary origin of antimatter in cosmic rays, which may require the inclusion of primary sources, typically classified into two scenarios: dark matter or astrophysical origin. Furthermore, the precise measurement of the proton flux performed by AMS-02 shows a progressive spectral hardening non-consistent with the traditional single power law predicted by the standard paradigm of cosmic ray propagation, which may be due to the injection of high rigidity protons by local accelerators or non-standard cosmic ray transport in the Galaxy. The measurement of the directionality of cosmic ray fluxes provides a complementary characterization of the features observed in their spectra and may help to understand the origin of these phenomena. In this context, a high sensitivity is required to determine the small signals that the new phenomena may induce in the cosmic ray fluxes. The absolute determination of the large scale anisotropy of a cosmic ray species requires the definition of the isotropy hypothesis in the analysis, which is given by a reference map corresponding to the directional response of the detector. In this context, this thesis presents a novel method in the construction of reference maps and a set of tools to determine the anisotropy of cosmic rays with space-based detectors, which are valid for any cosmic ray species. The method, which is based in the analysis in individual acceptance bins, does not require an explicit determination of the acceptance. On the other hand, detection effects, namely, variation of the efficiencies along the spacecraft orbit, are calculated in the specific coordinate system of analysis. Finally, a binned-likelihood fit is used to compare the sample and the reference map and provides the dipole components. The techniques developed in this thesis have been applied to the sample of cosmic ray electrons, positrons and protons collected by AMS-02 during its first five years of data taking, from May 2011 to May 2016. This thesis describes the strategy to achieve pure samples of electrons, positrons and protons by means of a cut-based selection on the variables measured by the different AMS-02 subdetectors. In addition, a dedicated study of the geographical variations of the detection efficiencies and their implications in the analysis of anisotropies in galactic coordinates is exhaustively presented. The measurement of the dipole anisotropy in galactic coordinates has been carried out in 8 cumulative rigidity ranges for protons, and 5 cumulative energy ranges for electrons and positrons, and are consistent with isotropy. As a consequence, 95% C.I. upper limits on the dipole anisotropy have been computed, and are found to be: 0.01 for protons above 300 GV; and 0.006 for electrons, and 0.02 for positrons in the energy range between 16 and 350 GeV.