Tesis doctoral de Francisco Salesa Greus
The exploration of the universe has fascinated the human being since ancient times. This exploration has been carried on mainly with the observation of the light, that is photons, arriving to the earth from extraterrestrial sources. The improvement of our knowledge in particle physics as well as the big advances in the development of our experimental techniques are allowing us to extend our universe exploration to the most energetic phenomena. For instance, photons exceeding 10 tev have been observed with current detectors, leading to the discovery of sources without counterpart in other wavelengths. Apart from photons, cosmic rays reaching the earth can also bring us important knowledge improving our understanding of the universe. Cosmic rays bombard our atmosphere continuously from the space with energies up to 10^20 ev. Presently, we have measured quite well the cosmic ray energy spectrum but, almost one hundred years after its discovery, their origin is still unknown. However, recent observations of very high-energy cosmic rays have started to clear up this mystery. Correlation of the most energetic cosmic rays (> 10^18 ev) with nearby extragalactic active galactic nuclei (agn) has been observed. Both, cosmic rays and photons, will complement each other in the exploration of the universe, in what has been called «multi-messenger approach». this multi-messenger approach needs to be completed with the neutrino. The main advantage of neutrinos with respect to cosmic rays is that the former, being neutral stable particles, can reach the earth without being detected by magnetic fields. Thus, they point back to their sources. This magnetic field deflection is negligible only for the most energetic cosmic rays, since they are charged particles. However, at those energies their spectrum starts to fall down critically due to the interaction of the cosmic rays with the relic photons from the cosmic microwave background (cmb). This effect is known as the gzk cutoff. The mean free path predicted in this case is about 50 mpc, so only nearby sources can be detected. Neutrinos are also advantageous with respect to photons because these are absorbed by the intergalactic medium when interacting with the extragalactic background light (ebl), mainly with optical/infrared radiation. Thus, it is not expected to detect high-energy photons (> 10 tev) from sources farther than 100 mpc. the feasibility of neutrino astronomy was confirmed by the detection of neutrinos emitted by the sun and the supernova sn 1987a. The observation of neutrinos coming from the sun meant an important breakthrough, since their flux showed a decit with respect to what is expected according to the solar standard model. This deficit was confirmed studying atmospheric neutrinos. The best solution to fix the problem is to assume that neutrinos have mass and so change the flavour by the process known as neutrino oscillations. This effect brought the first hint of physics beyond the standard model of particle physics. the main drawback when performing astronomy with neutrinos is that huge volumes are required to detect them because they interact only weakly with matter. The best way to obtain such big volumes is to use a natural medium as water or ice. That was the idea conceived by markov for constructing what is called a neutrino telescope. Some projects have taken on the challenge of constructing such neutrino telescopes. They aim to detect the cherenkov light induced by the charged particles produced by the interaction of a high-energy neutrino in the matter surrounding the detector. This light travels in a transparent optical medium, as water or ice, and then it is recorded by a three-dimensional array of photomultipliers. Finally, with the charge time and position information of the hits produced in the detector, the track can be deduced and thus the position of the event in the sky map is obtained. antares is one of the projects which has recently achieved the completion of one of this huge neutrino detectors. It consists on an array of almost 900 photomultipliers distributed in 12 strings deployed at 2475 m depth in the vicinity of the toulon coast in the mediterranean sea. It is currently taking data steadily. Antares is the biggest neutrino telescope deployed underwater and also the biggest at the northern hemisphere. this thesis work is divided in two main parts. The first one is devoted to the time calibration of the antares detector and the results obtained using the optical beacon calibration system. In the second part, the analysis to search for point sources with the data of the rst ve lines deployed of antares is presented. the first chapter summarizes the current status of the astroparticle physics field, specially focused on what concerns to high-energy neutrino astronomy. In the second chapter, a detailed description of the antares detector is given. The third chapter is dedicated to the detector time calibration, with a detailed explanation of the systems used to this end. The fourth chapter contains the results of the studies performed by the optical beacon system. The fifth chapter describes the monte carlo simulation and data processing used for the analysis of point-like sources. Finally, the sixth chapter presents the first results of point source search with the data from the detector.
Datos académicos de la tesis doctoral «Time calibrion and point source analsis with the antares neutrino telescope«
- Título de la tesis: Time calibrion and point source analsis with the antares neutrino telescope
- Autor: Francisco Salesa Greus
- Universidad: Universitat de valéncia (estudi general)
- Fecha de lectura de la tesis: 29/11/2010
Dirección y tribunal
- Director de la tesis
- Juan De Dios Zornoza Gómez
- Tribunal
- Presidente del tribunal: Antonio Ferrer soria
- jean pierre Ernenwein (vocal)
- heide Costantini (vocal)
- José Busto villaverde (vocal)