Dissertations / Theses on the topic 'Cosmic ray detections'

The identification of the relic particles which presumably constitute cold dark matter is a key challenge for astroparticle physics. Indirect methods for their detection using high energy astro- physical probes such as cosmic rays have been much discussed. In particular, recent ‘excesses’ in cosmic ray electron and positron fluxes, as well as in microwave sky maps, have been claimed to be due to the annihilation or decay of dark matter. In this thesis, we argue however that these signals are plagued by irreducible astrophysical backgrounds and show how plausible con- ventional physics can mimic the alleged dark matter signals. In chapter 1, we review evidence of, and possible particle candidates for, cold dark matter, as well as our current understanding of galactic cosmic rays and the state-of-the-art in indirect detection. All other chapters contain original work, mainly based on the author’s journal publications. In particular, in chapter 2, we consider the possibility that the rise in the positron fraction observed by the PAMELA satellite is due to the production through (hadronic) cosmic ray spallation and subsequent acceleration of positrons, in the same sources as the primary cosmic rays. We present a new (unpublished) analytical estimate of the range of possible fluctuations in the high energy electron flux due to the discreteness of plausible cosmic ray sources such as supernova remnants. Fitting our result for the total electron-positron flux measured by the Fermi satellite allows us to fix the only free parameter of the model and make an independent prediction for the positron fraction. Our explanation relies on a large number of supernova remnants nearby which are accelerating hadronic cosmic rays. Turning the argument around, we find encouraging prospects for the observation of neutrinos from such sources in km^3-scale detectors such as IceCube. Chapter 3 presents a test of this model by considering similar effects expected for nuclear secondary-to-primary ratios such as B/C. A rise predicted above O(100)GeV/n would be an unique confirmation of our explanation for a rising positron fraction and rule out the dark matter explanation. In chapter 4, we review the assumptions made in the extraction of the `WMAP haze' which has also been claimed to be due to electrons and positrons from dark matter annihilation in the Galactic centre region. We argue that the energy-dependence of their diffusion means that the extraction of the haze through fitting to templates of low frequency diffuse galactic radio emission is unreliable. The systematic effects introduced by this can, under specific circumstances, reproduce the residual, suggesting that the ‘haze’ may be just an artefact of the template subtraction. We present a summary and thoughts about further work in the epilogue.

A novel detector for ultra-high energy cosmic rays, and its prototype are discussed. It detects events with primary energy greater than 100 PeV. (1 PeV = 1000 TeV; 1EeV = 1000 PeV.) The detector operates by sensing the near-ultraviolet scintillation light of ionized nitrogen molecules created by the passage of ionizing particles in extensive air showers. (The concept is loosely based on the highly successful Fly's Eye detector situated at Dugway, Utah.) Typical events should consist of 1 to 100 EeV primary energy showers, with near-vertical cores, passing through the detector's field-of-view at distances of 1 to 20 km. The optical field of view of the hypothetical detector would be 60 degrees wide by several (≈ 3) degrees high and would look in a near-horizontal direction at a distant mountain range or other suitably dark background roughly 20 Ian away. A typical good location would be the rim of a canyon, looking slightly downward at the other side. The field-of-view would be subdivided into 3 or more thinner ''wedges'', 60 degrees wide by, perhaps, 1 degree high. A single detector provides timing and brightness information only. Three widely-separated detectors with overlapping fields-of-view provide sufficient data to determine the core location, the zenith and azinruthal angles of the core axis, and the absolute luminosity of the cascade. Interpretation of the luminosity data would be a challenge, but it should be possible to estimate primary energy from it. The advantage of this new scheme is the enormous effective detector area per relatively low-cost detector module. Each triplet of detectors "sees" 300 square km with a typical core axis acceptance of roughly 1 sr. The construction and testing of a prototype unit has been accomplished. The field-of-view was 41 degrees wide by 2 degrees high. Light was collected by a 4.7 square meter mirror and focused onto a wave-shifter PMT system. 8 events with primary energies in the 0.1 to 1 EeV range were observed in an 8.5 hour period. Representative events are shown and preliminary data analysis is discussed.

Les preuves pour l'existence de la matière noire (MN), sous forme d'une particule inconnue qui rempli les halos galactiques, sont issues d'observations astrophysiques et cosmologiques: son effet gravitationnel est visible dans les rotations des galaxies, des amas de galaxies et dans la formation des grandes structures de l'univers. Une manifestation non-gravitationnelle de sa présence n'a pas encore été découverte. L'une des techniques les plus prometteuse est la détection indirecte de la MN, consistant à identifier des excès dans les flux de rayons cosmiques pouvant provenir de l'annihilation ou la désintégration de la MN dans le halo de la Voie Lactée. Les efforts expérimentaux actuels se focalisent principalement sur une gamme d'énergie de l'ordre du GeV au TeV, où un signal de WIMP (Weakly Interacting Massive Particles) est attendu. L'analyse des mesures récentes et inédites des rayons cosmiques chargés (antiprotons, électrons et positrons) et leurs émissions secondaires et les améliorations des modèles astrophysiques sont présentées.Les données de PAMELA sur les antiprotons contraignent l'annihilation et la désintégration de la MN de manière similaire (et même légèrement meilleurs) que les contraintes les plus fortes venant des rayons gamma, même dans le cas où les énergies cinétiques inférieures à 10 GeV sont écartées. En choisissant des paramètres astrophysiques différents (modèles de propagation et profils de MN), les contraintes peuvent changer d'un à deux ordres de grandeur. Pour exploiter la totalité de la capacité des antiprotons à contraindre la MN, des effets précédemment négligés sont incorporés et se révèlent être importants dans l'analyse des données inédites de AMS-02 : ajouter les pertes d'énergie, la diffusion dans l'espace des moments et la modulation solaire peut modifier les contraintes, même à de hautes masses. Une mauvaise interprétation des données peut survenir si ces effets ne sont pas pris en compte. Avec les flux de protons et d'hélium exposé par AMS-02, le fond astrophysique et ces incertitudes du ratio antiprotons sur protons sont réévalués et comparés aux données inédites de AMS-02. Aucune indication pour un excès n'est trouvé. Une préférence pour un halo confinant plus large et une dépendance en énergie du coefficient de diffusion plus plate apparaissent. De nouvelles contraintes sur l'annihilation et la désintégration de la MN sont ainsi dérivés.Les émissions secondaires des électrons et des positrons peuvent aussi contraindre l'annihilation et la désintégration de la MN dans le halo galactique : le signal radio dû à la radiation synchrotron des électrons et positrons dans le champs magnétique galactique, les rayons gamma des processus de bremsstrahlung avec le gas galactique et de Compton Inverse avec le champs radiatif interstellaire sont considérés. Différentes configurations de champs magnétique galactique et de modèles de propagation et des cartes de gas et de champs radiatif interstellaire améliorés sont utilisées pour obtenir des outils permettant le calculs des émissions synchrotrons et bremsstrahlung venant de MN de type WIMP. Tous les résultats numériques sont incorporés dans la dernière version du Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID).Une interprétation d'un possible excès dans les données de rayons gamma de Fermi-LAT au centre galactique comme étant dû à l'annihilation de MN en canaux hadronique et leptonique est analysée. Dans une approche de messagers multiples, le calcul des émissions secondaires est amélioré et se révèle être important pour la détermination du spectre pour le canal leptonique. Ensuite, les limites provenant des antiprotons sur l'annihilation en canal hadronique contraignent sévèrement l'interprétation de cet excès comme étant dû à la MN, dans le cas de paramètres de propagation et de modulation solaire standards. Avec un choix plus conservatif de ces paramètres elles s'assouplissent considérablement
Overwhelming evidence for the existence of Dark Matter (DM), in the form of an unknownparticle filling the galactic halos, originates from many observations in astrophysics and cosmology: its gravitational effects are apparent on galactic rotations, in galaxy clusters and in shaping the large scale structure of the Universe. On the other hand, a non-gravitational manifestation of its presence is yet to be unveiled. One of the most promising techniques is the one of indirect detection, aimed at identifying excesses in cosmic ray fluxes which could possibly be produced by DM annihilations or decays in the Milky Way halo. The current experimental efforts mainly focus in the GeV to TeV energy range, which is also where signals from WIMPs (Weakly Interacting Massive Particles) are expected. Focussing on charged cosmic rays, in particular antiprotons, electrons and positrons, as well as their secondary emissions, an analysis of current and forseen cosmic ray measurements and improvements on astrophysical models are presented. Antiproton data from PAMELA imposes contraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds from gamma ray experiments, even when kinetic energies below 10 GeV are discarded. However, choosing different sets of astrophysical parameters, in the form of propagation models and halo profiles, allows the contraints to span over one or two orders of magnitude. In order to exploit fully the power of antiprotons to constrain or discover DM, effects which were previously perceived as subleading turn out to be relevant especially for the analysis of the newly released AMS-02 data. In fact, including energy losses, diffusive reaccelleration and solar modulation can somewhat modify the current bounds, even at large DM masses. A wrong interpretation of the data may arise if they are not taken into account. Finally, using the updated proton and helium fluxes just released by the AMS-02 experiment, the astrophysical antiproton to proton ratio and its uncertainties are reevaluated and compared to the preliminarly reported AMS-02 measurements. No unambiguous evidence for a significant excess with respect to expectations is found. Yet, some preference for thicker halos and a flatter energy dependence of the diffusion coefficient starts to emerge. New stringed constraints on DM annihilation and decay are derived. Secondary emissions from electrons and positrons can also be used to constrain DM annihilation or decay in the galactic halo. The radio signal due to synchrotron radiation of electrons and positrons on the galactic magnetic field, gamma rays from bremsstrahlung processes on the galactic gas densities and from Inverse Compton scattering processes on the interstellar radiation field are considered. With several magnetic field configurations, propagation scenarios and improved gas density maps and interstellar radiation field, state-of-art tools allowing the computaion of synchrotron and bremssttrahlung radiation for any WIMP DM model are provided. All numerical results for DM are incorporated in the release of the Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID). Finally, the possible GeV gamma-ray excess identified in the Fermi-LAT data from the Galactic Center in terms of DM annihilation, either in hadronic or leptonic channels is studied. In order to test this tantalizing interprestation, a multi-messenger approach is used: first, the computation of secondary emisison from DM with respect to previous works confirms it to be relevant for determining the DM spectrum in leptonic channels. Second, limits from antiprotons severely constrain the DM interpretation of the excess in the hadronic channel, for standard assumptions on the Galactic propagation parameters and solar modulation. However, they considerably relax if more conservative choices are adopted

The study of cosmic rays provides a rare view of the nature of the universe. The remote environment and flexibility of the Murchison Widefield Array make this radio telescope ideal for the intricate task of studying these cosmic rays. The research presented in this thesis has proved this to be achievable with a sensitivity and precision matched by few other instruments around the world.

This thesis concentrates on the measurement of cosmic-ray light component (proton + helium) spectrum with the Dark Matter Particle Explorer (DAMPE). In chapter one, an introduction on cosmic-ray history is given together with the acceleration mechanism and some recent experiments. A description on DAMPE system is presented in chapter two, which includes its sub-detectors, scientific targets and parameters. There are various challenges in measuring cosmic ray energy with a limited-size calorimeter (like the BGO of DAMPE). In chapter three, various unfolding methods for reconstructing the primary energy of cosmic ray nuclei are discussed. It turns out that the method based on the Bayes theorem has the best performance on reconstructing the cosmic-ray energy for DAMPE. The test results show that the Bayes method is capable of reconstructing nuclei energy with good accuracy on both MC samples (bias within 2%) and real data that come from the test beams at CERN (bias within 3%). In chapter four, a detailed description on the measurement of cosmic ray protons + helium spectrum is presented, which involves the candidates selection, energy reconstruction and calculation of the statistical and systematic uncertainties. Finally, the proton + helium spectrum with energy 40 GeV to 100 TeV is presented.

We have conducted an extensive experimental study on the subject of near ground atmospheric electricity. The main objective was to gain more understanding of this particular aspect of atmospheric phenomena, while testing the possible application to cosmic ray research. The results in atmospheric electricity show that there are certain patterns in ion grouping such as the size and lifetime. The average lifetime of ion group is 0.7 seconds and the average size is about 10 meters at our experimental site. Ultrahigh energy cosmic ray air showers should create sizable slow atmospheric electric pulses according to our theoretical calculations. Preliminary studies on air showers with total particle number N equal or greater than 10⁵ (10¹⁵ eV) have yielded strong evidence that slow atmospheric current pulses are associated with air showers. The theory and the experiment agree with each other fairly well when we average over large numbers of events. With our current experimental arrangement, when the air shower exceeds a certain size, the system response saturates. Therefore it is extremely desirable in future research that the counter array be designed for a much higher threshold level, since this prototype experiment indicates that interesting data would be obtained. Another reason for further experimental research being directed toward ultrahigh energy, e.g., N ≥ 10⁷ (10¹⁷ eV) and higher, is to establish a calibration of the slow atmospheric electric signals generated by cosmic rays as a function of primary cosmic ray energy and core location. This type of slow atmospheric electric signal, if fully understood and calibrated, offers a new and potentially less expensive technique to observe ultrahigh energy cosmic ray events, which hold some fundamental keys to the knowledge of the universe on a large scale.

Cette thèse est dédiée à l'étude de la propagation des électrons et positrons cosmiques dans la Voie Lactée ainsi qu'à la détection indirecte de matière sombre. L'existence de la matière sombre dans l'Univers est une hypothèse raisonnable du point de vue de la cosmologie, de l'astrophysique mais également de la physique des particules. Pourtant sa détection nous échappe encore et il n'est pas possible de vérifier la validité de cette hypothèse autrement que par des moyens faisant intervenir la gravitation. L'une des voies possibles pour la détection de la matière sombre et la compréhension de ses propriétés, consiste à chercher les produits de son annihilation ou de sa désintégration dans les rayons cosmiques Galactiques. Durant ces trois dernières années, les données concernant les flux d'électrons et de positrons cosmiques se sont accumulées et ont atteint des précisions remarquables. Une telle précision expérimentale exige que l'on raffine les modèles théoriques et que l'on quantifie les erreurs. Cette thèse s'efforce donc de recenser et de quantifier toutes les sources d'incertitudes des prédictions de flux d'électrons et de positrons cosmiques, qu'ils soient primaires ou secondaires, classiques ou exotiques. La plus grande attention a été portée sur les sources et la propagation dans le halo Galactique. De plus, une étude des émissions gamma et radio associées à ces rayons cosmiques est présentée, toujours avec la même volonté de mesurer les incertitudes. Enfin, un état des lieux de la recherche de détection de l'annihilation ou de la désintégration de la matière sombre galactique est présenté
This thesis is dedicated to the study of propagation of cosmic electrons and positrons in the Milky Way and to the indirect detection of dark matter. The existence of dark matter is a hypothesis considered as reasonable from the point of view of cosmology, astrophysics and even particle physics. Nevertheless its detection still eludes us and it is not possible to verify this hypothesis by other means than gravitational one. A possible way to detect dark matter is to look for its annihilation or decay products among Galactic cosmic rays. During the last three years, data concerning cosmic ray electrons and positrons have been accumulated and have reached a remarkable precision. Such a precision requires from us to refine the theoretical models and to quantify the errors. This thesis addresses the study of all the sources of uncertainties affecting predictions of cosmic electrons and positron fluxes, primary and secondary, classical or from exotic origin. The greatest care has been dedicated to the sources and the propagation in the Galactic halo. Moreover a study of gamma and radio emissions associated to these cosmic rays is presented, again with the will of sizing uncertainties. Finally a status of the research for detection of annihilation or decay of Galactic dark matter is presented

Cosmic rays at energies 10^18 eV and above are known as Ultra High Energy Cosmic Rays (UHECR). UHECR are charged particles that are accelerated by the biggest accelerators in our universe. Candidate accelerators generating these UHECR are super novas, black holes and neutron stars. But where and what these intergalactic accelerators is at large still unknown. One of the experiments in the forefront of research in this eld is JEM-EUSO, a planed space based telescope for detecting UHECR particles as they enter Earth's atmosphere. Made possible by the advances in photon detectors and light weighted Fresnel lenses. A ground based path nder experiment was carried out in 2015 called EUSO-TA to test the optics and photomultiplier technologies. When the UHECR enters the atmosphere it collides with the atoms generating a number of secondary particles which in turn interacts with other atoms in the atmosphere generating a cascade of secondary particles. These trails are known as Extensive Air Showers (EAS). Mostly electrons are generated and in turn they excites the nitrogen atoms in the atmosphere which generate a isotropic characteristic uorescence light. The JEM-EUSO telescope is designed to detect and measure the photon ux. From the photon ux it will be able to estimate the energy of the initial UHECR. JEM-EUSO will cover the largest area of EAS search and increase statistics of UHECR data. This thesis describes the method and development of algorithms made for EAS analysis and detection based on EUSO-TA data. A simulation of EUSO-TA focal surface was developed, simulating background, stars and EAS. The algorithms developed involves a background subtracting lter, line detection using Hough transform and a neural network for decision making. The Hough transform is used in computer vision and is a method used to detect lines in the pictures. It successfully identi ed both simulated and captured UHECR incoming direction with small errors. Neural network are a machine learning method used classi cation and regression problems. With the use of know example data simulated or real captured data a neural network can without explicit programing it, adjust its parameters to t the data. Based on method called supervised learning. The algorithms was programed in Python and using ROOT software to build the neural network. The resulting algorithm was able to successfully detect simulated data. Test on the EUSO-TA captured data shows a promising result but has to be developed and tested further.

Muon tomography represents a new type of imaging technique that can be used in detecting high-Z materials (such as shielded HEU). As muons pass through materials, they continuously lose energy via ionisation and can stop within a material. Upon stopping secondary processes can occur, which result in the production of excess neutrons and gamma-rays. Due to their high energies most muons can pass through large depths of different materials. These muons will also undergo multiple scattering. Previous radiographic methods that looks to differentiate high-Z materials from low-Z clutter tend to be based on multiple scattering of muons only. Presented is the development of two new types of analysis algorithm, which makes use of the different interactions cosmic-ray muons undergo when passing through a material. The first algorithm developed makes use of the multiple Coulomb scattering that a muon will undergo. This involves using a novel density based clustering approach that ascertains regions of high-Z material placed within an inspected volume. The capability of this new type of algorithm has been tested under realistic scenarios. These scenarios involve placing shielded HEU in cargo containers filled with a variety of different clutter. The algorithm has been shown to be efficient in detecting shielded HEU amongst low-Z clutter, but struggles upon the introduction of blocks of aluminium, or materials with densities higher than this. Whereas previous radiographic methods were based on multiple scattering of muons only, the second developed algorithm uses muon absorption on nuclei to enhance the detection capabilities of the scattering technique. In particular, the goal is to improve on the distinction between high-density materials and low-density clutter. Muons will more readily lose energy in higher density materials. Therefore multiple muon disappearances within a localised volume may signal the presence of high-density materials. Muons that disappear have their track evaluated using a 3D line extrapolation algorithm, which is in turn used to construct a 3D tomographic image of the inspected volume. The ability to differentiate between materials using the 3D line extrapolation algorithm is established. The technique of muon disappearance has been applied to identifying shielded HEU in realistic scenarios. Despite being capable of identifying shielded HEU in otherwise empty cargo containers, multiple additional regions (due to the lorry and container itself) were misclassified as possible threat materials. This makes accurate detection systems that solely use this technique for shielded HEU unlikely. However, since the build-up of nuclear materials was apparent, we have demonstrated how this technique can be used as a supplementary technique to help enhance muon scattering tomography capabilities. This is done through first identifying `areas of interest' using muon scattering tomography before confirming whether they are threats or other materials with the muon disappearance algorithm. It is concluded that while muon disappearance can slightly enhance the capabilities of muon scattering tomography, muon scattering still remains the most efficient method for detection of nuclear materials.

Identifying what makes up the Dark Matter is a long-standing problem to which the abundance of gravitational and cosmological evidence fails to answer. Indirect detection techniques have the aim to unveil the nature of Dark Matter by catching and identifying the products of potential decays and/or annihilations. The work exposed in this thesis is in line with this strategy and has for common thread the quest for line(-like) features in the extraterrestrial fluxes of gamma-rays and neutrinos. The motivation behind this specific interest is that, due to the absence of astrophysical counterparts beyond the GeV scale, these features constitute the ultimate probes (also called “smoking guns”) of the existence of Dark Matter.The thesis is organized in three Parts, the first of which is an introduction to the different facets of the Dark Matter conundrum and why it is not a trivial issue. The works involving gamma-ray line considerations are gathered in Part II, and those exclusively focusing on neutrino lines in Part III.Part II focuses on the effective field theory of Dark Matter decay, first in the context of millicharged particles decaying to gamma-ray lines, and then in the context of (neutral and millicharged) Dark Matter decays involving the simultaneous emission of gamma-ray and neutrino lines. In both cases, the simultaneous emission of cosmic rays is unavoidable and the decays are constrained in a multi-messenger fashion. The complementarity of the results obtained is used to derive model-independent constraints on the Dark Matter lifetime, and shows the possibility to exclude or distinguishsome specific scenarios on the basis of an explicit experimental conjecture.After an introduction to the neutrino detection principles and to the operation of the IceCube detector, Part III focuses on two careful searches for spectral features in the neutrino spectrum. The main goal behind these analyses, conducted in two different regions of the energy spectrum but using the same likelihood ratio procedure, is to popularize dedicated energy distribution studies by showing their ability to reach sensitivity levels comparable to—sometimes even going beyond—those obtained with angular distribution studies or even in the context of gamma-ray line searches.
Option Physique du Doctorat en Sciences
info:eu-repo/semantics/nonPublished

This thesis is concerned with the detection of very high energy cosmic gamma rays using the atmospheric Cerenkov technique. A general introduction to gamma ray detection techniques is followed by a detailed discussion of the principles of the atmospheric Cerenkov technique and the history of its use prior to this work. The design and operation of the University of Durham facility in Dugway, Utah is described in depth. Monte Carlo computer simulations have been developed to assist in both the understanding of the equipment and the analysis of the results for the Durham facility. The variation of the response of the array with zenith angle and detector threshold has been investigated and the aperture function of a single telescope calculated. The latter has been found to be a complicated function of both zenith angle and detector threshold. Computer simulations have also been developed to aid in the design of a camera to record two-dimensional Cerenkov light images from small extensive air showers, and to provide a means of testing analysis routines; these are discussed. The camera is located at the F.L. Whipple Observatory in Arizona. The techniques employed in the analysis of data recorded by the Dugway facility are discussed, and a computer package developed to aid in the routine aspects of the analysis is described. Results of observations from two sources, Cygnus X-3 and PSR0531, are presented, with particular reference to periodicities inherent in the sources and to bursts of gamma ray emission. The discussion of the results includes a review of the various models which have been proposed for Cygnus X-3.

Plus d'un siècle après leur découverte, les rayons cosmiques continuent d'intriguer les physiciens. Le flux de ces particules d'origine extraterrestre décroît fortement en fonction de leur énergie. Au-delà de 1 PeV(10¹⁵ eV), le flux devient trop faible pour permettre la détection directe sur des échelles de temps raisonnables. Cependant, les cascades de particules secondaires créées après l'interaction des rayons cosmiques avec les constituants de l'atmosphère sont détectables depuis le sol, c'est la détection indirecte. A partir de 100 PeV, le nombre d'observations est trop faible pour estimer de manière précise la masse des rayons cosmiques et ainsi contraindre les modèles de mécanismes d'accélération, de propagation et de type de sources. La détermination de la composition est effectuée à l'Observatoire Pierre Auger par les télescopes de fluorescence via la mesure de la variable Xmax avec un cycle utile de 14%. Xmax est la profondeur d'atmosphère traversée à laquelle le nombre de particules secondaires atteint sa valeur maximale. Cette observable est fortement corrélée à la masse du rayon cosmique qui a initié la gerbe. Un grand nombre d'observations est requis pour effectuer une détermination précise de la masse car les fluctuations statistiques de Xmax sont importantes. La radio détection apparaît alors comme une excellente alternative à la détection par fluorescence, puisque la technique mesurant ce signal a un cycle utile proche de 100%. Cette thèse propose une méthode d'estimation de la masse des rayons cosmiques d'ultra haute énergie basée seulement sur l'étude des signaux radio et leur simulation, afin de reconstruire de manière systématique l’énergie, le cœur et la profondeur Xmax des gerbes détectées par l’expérience AERA sur le site de l'Observatoire Pierre Auger en Argentine. L'influence de la modélisation de l'atmosphère dans le code de simulation SELFAS sur les valeurs reconstruites est étudiée. Notamment la géométrie des couches atmosphériques, la manière de traiter l'indice de réfraction et la densité de l'air ainsi que leurs variations journalières et saisonnières
More than a century after their discovery, cosmic-raysare still puzzling physicists. The flux of these particlescoming from extraterrestrial sources strongly decreasesas a function of their energy. Above 1 PeV (10¹⁵ eV), theparticle flux becomes too low to allow a direct detectionon a reasonable time scale. However, the cascades ofsecondary particles produced after the interaction ofcosmic-rays with the constituents of the atmosphere aredetectable at the ground level; it is the indirect detection.Above 100 PeV, the number of observations is too lowto accurately estimate the mass of the cosmic rays andthen to constrain the prediction models of accelerationmechanisms, propagation and type of sources. Thedetermination of their composition is achieved at thePierre Auger Observatory using fluorescencetelescopes from the measurement of the Xmaxobservable with a duty cycle of 14%. Xmax, defined asthe atmosphere depth at which the number ofsecondary particles reaches its maximal value, is highlycorrelated to the mass of the cosmic ray that hascreated the air shower. A large number of observationsis required for a precise estimation of the mass as theXmax statistical fluctuations are important. The radiodetection is a perfect alternative to the fluorescencemethod as the duty cycle of a typical radio detector isclose to 100%. This thesis proposes a method toestimate the mass of ultra-high energy cosmic raysusing only the radio signals and their simulation. Thegoal is to systematically reconstruct the Xmax depth ofeach air shower detected by the AERA experimentwithin the site of the Pierre Auger Observatory inArgentina. The influence of the description of theatmosphere on the reconstructed shower parameters, inthe SELFAS code, has been studied. It includes thegeometry of the atmospheric layers, the way to calculatethe air refractive index and density, as well as their dailyand seasonal fluctuations

A search for a diffuse flux of cosmic neutrinos with energies in excess of 10¹⁴ eV was performed using two years of AMANDA-II data, collected in 2003 and 2004. A 20% evenly distributed sub-sample of experimental data was used to verify the detector description and the analysis cuts. A very good agreement between this 20% sample and the background simulations was observed. The analysis was optimised for discovery, to a relatively low price in limit setting power. The background estimate for the livetime of the examined 80% sample is 0.035 ± 68% events with an additional 41% systematical uncertainty.

The total neutrino flux needed for a 5σ discovery to be made with 50% probability was estimated to 3.4 ∙ 10^-7 E^-2 GeV s^-1 sr^-1 cm^-2 equally distributed over the three flavours, taking statistical and systematic uncertainties in the background expectation and the signal efficiency into account. No experimental events survived the final discriminator cut. Hence, no ultra-high energy neutrino candidates were found in the examined sample. A 90% upper limit is placed on the total ultra-high energy neutrino flux at 2.8 ∙ 10^-7 E^-2 GeV s^-1 sr^-1 cm^-2, taking both systematical and statistical uncertainties into account. The energy range in which 90% of the simulated E^-2 signal is contained is 2.94 ∙ 10¹⁴ eV to 1.54 ∙ 10¹⁸ eV (central interval), assuming an equal distribution over the neutrino flavours at the Earth. The final acceptance is distributed as 48% electron neutrinos, 27% muon neutrinos, and 25% tau neutrinos.

A set of models for the production of neutrinos in active galactic nuclei that predict spectra deviating from E^-2 was excluded.

Der TAIGA Detektor (“Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy”) testet eine neue Nachweismethode der erdgebundenen Cherenkov Gamma Astronomie fuer 10TeV bis einige PeV, und fuer kosmische Strahlung oberhalb 100TeV: die Kombination abbildender und nicht-abbildender Cherenkov Detektoren in einem hybriden System. Im Fokus der Arbeit steht TAIGA-HiSCORE - ein Cherenkov Detektorfeld mit grosser Apertur zur Messung der Zeitstruktur der Cherenkovlichtfront in atmosphaerischen Luftschauern (EAS). Die Praezisonsvermessung der Schauerrichtung basiert auf (1) sub-nsec Zeitsynchronisation aller Detektoren, und (2) einer neuentwickelten Zeitkalibrationsmethode. Die Genauigkeit wird bestimmt mit experimentellen und simulierten EAS-Daten, spezieller LED-Kalibration und dem LIDAR Laserstrahl aus der International Space Station (ISS). Mit den HiSCORE9 Daten (2013-2014) wird die sub-nsec Zeitsynchronisation durch das White Rabbit Zeitsystem unter realen Bedingungen nachgewiesen. Eine neue, auch fuer grosse Cherenkov-Detektorfelder praktikable Zeitoffset-Kalibration aller Detektoren wurde entwickelt, und fuer HiSCORE28 (2015-2018) angewandt. Diese hybride Kalibration basiert auf EAS-Ereignissen und direkter LED-Kalibration fuer lediglich eine begrenzte Zahl von Detektoren. Die Genauigkeit der Luftschauer-Richtungsrekonstruktion wird ueber die “Schachbrett-Methode” MC-unabhaengig bestimmt zu 0.4° an der Energieschwelle (50TeV) und <= 0.2° fuer > 100TeV. Eine wichtige Zufallsentdeckung war mit HiSCORE28 moeglich: der Laser des ISS-CATS-Lidars wurde in richtungsrekonstruierten Daten von HiSCORE28 nachgewiesen. Mit den “ISS Ereignissen” gelang es, sowohl die Rekonstruktionsgenauigkeit von HiSCORE, als auch das “absolute pointing” zu messen (<=0.1°) - besonders wichtig, da eine starke Gamma-Quelle im Datensatz bisher nicht nachgewiesen wurde. Im Schlussteil der Arbeit wird ein Methode zur Punktquellensuche im gesamten Gesichtsfeld von TAIGA-HiSCORE vorgestellt.
The TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) detector is a new ground-based Cherenkov detection technology for gamma-astronomy from 10TeV up to several PeV, and cosmic rays (CR) above 100TeV. The main topic of this work is TAIGA-HiSCORE, the wide-aperture air Cherenkov timing array. The focus is on precision extensive air shower (EAS) arrival direction reconstruction, achieved by (1) sub-nsec time-synchronization between the array stations, and (2) a newly developed array time calibration procedure. The performance is verified using simulated and experimental data from EAS, dedicated LED calibration, and a LIDAR laser beam from the International Space Station (ISS). The analysis of the HiSCORE 9 data (2013-14), collected with a data acquisition system (DAQ) based on the White Rabbit (WR) timing system, allows to verify the sub-nsec time synchronization between the array stations. The analysis of HiSCORE 28 data (2015-2018) addresses the problem of achieving an easy-to-perform time calibration for large area ground-based Cherenkov array. A new "hybrid" calibration method is developed, which makes use of EAS data, and requires direct LED calibration of only a few array stations. The "chessboard" method is applied on the reconstructed data to obtain a MC-independent estimation of the detector angular resolution, found to be 0.4° at threshold (~50TeV) and <= 0.2° above 100TeV. A serendipitous discovery was made in this work: a signal from the CATS-LIDAR on-board the ISS was found in the HiSCORE 28 data. These "ISS-events" are used to verify the detector performance, in particular the absolute angular pointing (<= 0.1°), particularly important since a strong gamma point source has not yet been detected by the TAIGA-HiSCORE. The final part of the work presents a first preliminary approach to a wide aperture point source analysis, developed for the TAIGA-HiSCORE in stand-alone operation.

Des de temps immemorials, dels principis de la humanitat, els éssers humans han mostrat un tremenda curiositat i atracció pel que veien quan enlairaven la vista. Per un motiu o un altra, la recerca d'explicacions de naturalesa mística de tot allò que envoltava la vida humana així com el propi destí es buscava fora de la Terra. Aquest interès místic va fomentar la observació del cel nocturn que al cap del temps junt amb altres canvis de tipus filosòfic i social van donar peu a una interpretació racional del que observaven i per tant, a una primera formulació de models cosmogònics i cosmològics.
Precisament el llegat d'aquests primers observadors del cel ha estat la curiositat per l'espai extraterrestre per buscar-hi respostes a diferents preguntes. Algunes d'aquestes preguntes, que han estat formulades per diversos científics, varen consistir en les llavors per a una nova disciplina cultivada en el camp de la ciència física: La física dels Raigs Còsmics.
Actualment, la física dels Raigs Còsmics consisteix en una disciplina que aixopluga diferents tòpics de l'astrofísica i la física com ara la nucleosíntesi dels raigs còsmics, el procés de injecció, els mecanismes d'acceleració, el procés de propagació i la detecció prop de la Terra dels raigs còsmics.
Durant els anys 80, es van planejar un conjunt d'experiències a bord de satèl·lits amb la finalitat d'estudiar la component hadrònica de la radiació còsmica, en concret, els ions ultrapesants amb càrrega superior a la del Ferro. El present treball està unit a un d'aquest experiments: l'UHCRE (Ultra Heavy Cosmic Ray Experiment). Varis apilaments de detectors sòlids de traces nuclears van ser usats en l'UHCRE. Aquests apilaments han estat analitzats i mesurats en el nostre grup, reconeixent un total de 205 traces originades per ions ultrapesants de la radiació còsmica. La identificació d'aquests ions en l'UHCRE ha estat la primera motivació d'aquest treball, així la primera meitat (capítols 1 i 2) d'aquesta tesi tracta aquest problema. D'altra banda, els capítols 3 i 4, concerneix el procés de propagació de l'abundància d'aquests ions cap a les seves fonts mitjançant el model de Leaky Box.
En el capítol 1, es presenta un mètode d'identificació conegut com Gradient Fraccional de la velocitat d'atac reduïda i es realitza un estudi detallat del seu rang d'aplicabilitat. Finalment, s'efectua la determinació de l'abundància dels raigs còsmics ultrapesants amb Z > 65 vistos per l'UHCRE.
En el capítol 2, s'utilitza un model alternatiu de formació de traça latent basat en el model de pèrdua d'energia restringida en el qual s'inclouen la possible contribució de les diferents correccions per col·lisions properes en l'equació de Bethe-Bloch. Un estudi prenent els resultats de l'UHCRE permet establir relacions entre els paràmetres que intervenen en el procés d'identificació. Finalment, s'obté una estimació d'aquests paràmetres usant dades experimentals d'accelerador.
En el capítol 3, es dedueix l'equació de transport pel model de Leaky Box (MLB) que descriu la variació de la composició química de la radiació còsmica durant el seu viatge a través de la galàxia. L'abundància en les fonts que es dedueix dels resultats de l'UHCRE és estimada resolent les equacions de transport per a tots els elements amb càrrega entre 65 i 92 mitjançant un mètode numèric que cal entendre'l com una primera aproximació al problema.
En el darrer capítol, les equacions del MLB es resolen numèricament usant la Weighted Slab Technique. Es presenta un estudi de la resposta d'aquest model quan es varien les expressions dels diferents paràmetres de propagació que es requereixen. Optimitzant el paràmetre estadístic χ² entre l'abundància calculada la qual és afectada per una indeterminació en la càrrega i l'abundància experimental, ah estat possible determinar aquella combinació de totes les expressions disponibles dels paràmetres de propagació que millor reprodueix l'abundància experimental de l'UHCRE.
Since ancient times, from the beginning of humankind, human beings have shown a great curiosity and attraction for what they saw when looking up. For one reason or another, the quest for explanations of mystical nature (maybe justifications) for what surrounded human life as well as its destiny was searched outside the Earth. This mystical interest encouraged the observation of the night sky which, in time, together with other social and philosophical changes, lead to a rational interpretation of what they observed and, hence the formulation of the first cosmogonical models and then cosmological models.
Precisely, the legacy of these first sky observers, has been the curiosity for the extraterrestial space in search of answers to many different questions. Some of these questions formulated by several scientists, were the seeds for a new discipline sowed in the field of physics science: Cosmic Ray Physics.
Nowadays, Cosmic Ray Physics consist on a discipline allowing to gather several different topics of astrophysics and physics such as the nucleosynthesis of cosmic rays, the injection process, the acceleration mechanisms, the propagation process and the detection of cosmic rays near the Earth.
During the 80's, a set of experiences on board of satellites were planned and carried out with the aim of studying the hadronic component of cosmic rays, specifically ultra heavy ions with charge higher than Iron. The present work is, therefore, linked to one of such experiences; the UHCRE (Ultra Heavy Cosmic Ray Experiment). Several stacks of sheets of solid state nuclear track detectors used in the UHCRE have been analysed and measured by our group, recognizing a total of 205 tracks as originated by ultra heavy cosmic ray ions. The identification of cosmic ray ions recorded in UHCRE has been the first motivation of this work, so the first half (chapter 1 and 2) of the present thesis deals with this problem. On the other hand, chapters 3 and 4 concern to the propagation process of the abundances of such ions back to their sources using the Leaky Box model.
In chapter one, an identification method, known as Reduced Etch Rate Fractional Gradient (RERFG) is presented and a detailed study of its range of applicability is performed. The determination of the abundances of ultra heavy cosmic ray with Z > 65 seen by the UHCRE is realized.
In the second chapter, an alternative track formation model based on a modification of the Restricted Energy Loss model is taken into consideration by introducing the contribution of the close collisions corrections in the Bethe-Bloch formula. A study taking the UHCRE measurements allows to establish relationships between the parameters involved in the identification process. Finally, an estimation of these parameters is made using experimental data from accelerator.
In chapter three, the transport equation for the Leaky Box Model (LBM) which describes the variation of the chemical composition of cosmic rays during their travel through the Galaxy is deduced. The source abundances inferred from the UHCRE results are estimated solving the transport equations, corresponding to all elements with charge 65 < Z < 92, with a numerical method that has to be understood as a first approximation to the problem.
In the last chapter, the LBM transport equations are numerically solved using the Weighted Slab Technique. A study of the response of the LBM is presented when different expressions of the required propagation parameters are taken. By optimizing the χ² statistical parameter between calculated abundances which are effected by a charge uncertainty and experimental abundances, it has been possible to determine which combination of all available expressions of the propagation parameters better reproduces the experimental abunadances of UHCRE.

Prise en compte des antiprotons pour la propagation des rayons cosmiques. Mise en evidence d'une source d'antineutrinos particuliere: l'ensemble des centrales nucleaires terrestres. Utilisation de ces antineutrinos pour etudier les oscillations de neutrinos dans le vide et dans la matiere. Application aux neutrinos emis par sn 1987a

Under the name EUSO, or Extreme Universe Space Observatory, are multiple instruments where some are currently under design or construction and others have concluded their mission. The main goal they have in common is to detect and analyse cosmic rays with very high energies by using the Earth's atmosphere as a detector. One instrument is called Mini-EUSO, will be placed on the international space station during 2019, and its engineering model is currently being used to collect data and test the function of different components. The engineering model differ from the full scale instrument, and it is also possible to use it for other purposes as well. In this thesis, some of the collected data is used to analyse and compare the engineering models specification to the full Mini-EUSO instrument, with focus on field of view, inert areas on the sensor and its general function. Objects, such as stars, meteors and satellites were also detected, and used in the tests. In addition a short test regarding the possibility to use the instrument to detect plastic residing in the ocean is made, by utilizing fluorescent properties of the plastics. The thesis came to the conclusion that some adjustments needed to be made on the engineering model, but also that the specifications of it was within expected ranges. Several of the objects found can also be used to improve detection algorithms. In addition, the preliminary tests regarding plastic detection in the ocean, have positive results.

In this work we made use of the AMICO algorithm to detect clusters in COSMOS2015, a photometric galaxy catalogue of the COSMOS field (Laigle+16). We divided our study in two different analyses being the cluster search on r-band photometry in the range 0