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Theses

Search for populations of unresolved sources of high energy neutrinos with the ANTARES neutrino telescope

Abstract : Astroparticle physics is a branch of physics related to the study of the most violent astrophysical phenomena in the Universe such as Active Galactic Nuclei (AGN) or Gamma Ray Bursts (GRB), which emit different cosmic messengers such as neutrinos, gravitational waves, electromagnetic radiation and charged particles. A proper understanding of these objects involves then a multi-messenger approach, in which neutrinos play a fundamental role. Thanks to their physical properties, neutrinos allow us to explore the physical phenomena produced in the densest astrophysical environments and to observe the Universe at large distances. This thesis is divided into three main parts. The first part is composed by three chapters dedicated to the scientific context in which the rest of the thesis is developed. In the first chapter, the scientific motivations for the search of high energy cosmic neutrinos are described. In chapter 2, a description of the main properties of AGN are given. These sources have been chosen as "test" objects in the research of potential neutrino sources. Finally, the third chapter is dedicated to the detection principle and main results of the currently operating neutrino telescopes. The second part of the thesis is dedicated to the technical description of the ANTARES neutrino telescope, and composed of two chapters. Chapter 4 describes the ANTARES telescope, the data acquisition and the data selection. In the last part of this chapter, the work made to measure the efficiency loss of the photomultipliers (PMTs) by using the baseline rates is described. Chapter 5 is dedicated to the Monte Carlo simulations. The different simulation packages used by the ANTARES collaboration are presented, and the different simulated processes are described. A contribution to the official package for the generation of neutrino interactions, relative to the implementation of the propagation and decay of the tau leptons, is described. The third part is dedicated to the search of potential cosmic signals in the events recorded by ANTARES. It comprises four chapters. Chapter 6 is a description of the signal search method, chapter 7 presents the principles of an analysis based on a 2 point correlation function that will be applied in chapter 9 with the purpose of searching for an excess of cosmic neutrinos characterized by an expected spatial distribution which is different from that of atmospheric neutrinos. This method is well suited for the detection of the collective effect produced by populations of weak point-like sources. Chapter 8 describes the simulation of the neutrino flux emitted by AGN. By using the luminosity function for different AGN classes obtained from X-ray observations, and the ANTARES acceptance, neutrinos coming from AGN populations are simulated as a function of two parameters which are related to the number of sources in the population, and to their luminosities. The analysis of these populations with the 2 point correlation function is detailed in chapter 9.
Keywords : Astroparticles
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  • HAL Id : tel-01662335, version 1

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Rodrigo Gracia Ruiz. Search for populations of unresolved sources of high energy neutrinos with the ANTARES neutrino telescope. Astrophysics [astro-ph]. Université Sorbonne Paris Cité, 2016. English. ⟨NNT : 2016USPCC150⟩. ⟨tel-01662335⟩

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