Orientador: Jose Augusto Chinellato / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-09T22:35:29Z (GMT). No. of bitstreams: 1 Perassa_EderArnedo_M.pdf: 7742499 bytes, checksum: 5f8e2630e2b11b5f5965e6b95c19be9b (MD5) Previous issue date: 2007 / Resumo: Neste trabalho são estudados os métodos de estatística bayesiana e máxima entropia na análise de dados. É feita uma revisão dos conceitos básicos e procedimentos que podem ser usados para in-ferência de distribuições de probabilidade. Os métodos são aplicados em algumas áreas de interesse, com especial atenção para os casos em que há pouca informação sobre o conjunto de dados. São apresentados algoritmos para a aplicação de tais métodos, bem como alguns exemplos detalhados em que espera-se servirem de auxílio aos interessados em aplicações em casos mais comuns de análise de dados / Abstract: In this work, we study the methods of Bayesian Statistics and Maximum Entropy in data analysis. We present a review of basic concepts and procedures that can be used for inference of probability distributions. The methods are applied in some interesting fields, with special attention to the cases where there¿s few information on set of data, which can be found in physics experiments such as high energies physics, astrophysics, among others. Algorithms are presented for the implementation of such methods, as well as some detailed examples where it is expected to help interested in applications in most common cases of data analysis / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física

Les rayons cosmiques ont été découverts il y a un siècle par Victor Hess à bord d'un vol scientifique en ballon. La physique des rayons cosmiques et les ballons stratosphériques ont partagé depuis lors une histoire commune, que ce soit pour d'authentiques découvertes ou en utilisant les ballons comme plateformes de test technologique pour de nouvelles missions satellites. Cette thèse, développée au sein de la collaboration JEM-EUSO, traite d'un démonstrateur en ballon stratosphérique. Notre but scientifique final est l'étude des Rayons Cosmiques de Ultra-Haute Energie (RCUHE), les particules les plus énergétiques connues dans l'Univers. Les RCUHES ont des énergies macroscopiques de plus de 10^20eV mais étant extrêmement rares, leurs origines sont encore inconnues. Ces derniers pénètrent notre atmosphère à une fréquence de un par km2 par siècle, produisant une gerbe atmosphérique géante, détectable notamment par la lumière de fluorescence ultraviolette qu'elle émet. Le principe de détection proposé par notre collaboration consiste dans l'utilisation d'un observatoire spatial, JEM-EUSO. Son objectif est d'observer un très grand volume d'atmosphère afin d'enregistrer un nombre significatif des événements ultra-violet de fluorescence initiés par les RCUHEs. Le démonstrateur EUSO-Ballon a été développé par la collaboration JEM-EUSO dans le but de démontrer les technologies et méthodes utilisées par le futur instrument spatial. Le 25 août 2014, EUSO-Ballon a été lâché depuis la base de ballons stratosphériques de Timmins (Ontario, Canada) par la division ballon du CNES. L'instrument a fonctionné pendant toute une nuit astronomique, observant depuis 38km d'altitude la lumière UV provenant de divers types de sols et de centaines de gerbes atmosphériques simulées. Ces dernières ont été produites par des flashers et un laser embarqués dans un hélicoptère volant sous EUSO-Ballon pendant deux heures. Ces résultats ont été rendus possibles par la restitution de l'attitude de l'instrument effectuée à l'IRAP, c'est-à-dire une analyse exhaustive des données du vol des différents appareils de mesure d'attitude de la nacelle du ballon. Une caractérisation précise de chaque sous-système était aussi indispensable à l'exploitation des données du vol. Le système optique innovant, composé de deux grandes lentilles de Fresnel, a été intégré et entièrement testé à l'IRAP. Face au large système réfractif de l'instrument, une nouvelle méthodologie de test a été développée. Les performances de l'optique, efficacité et spot focal, ont ainsi été mesurées et se sont révélées étonnamment différentes des prédictions des modèles numériques. Ces mesures sont utilisées pour l'analyse des données du premier vol et pour mieux comprendre le comportement de ces toutes nouvelles optiques, éléments clés dans la conception de l'instrument JEM-EUSO. / A century ago Cosmic Rays were discovered by Victor Hess during one of the very first scientific balloon flights. Ever since, Cosmic Ray physics and stratospheric balloons have shared a common history - either through genuine discoveries or by using balloon platforms as technology test beds for new satellite missions. This thesis, carried out within the JEM-EUSO collaboration, is about such a pathfinder balloon mission. Our ultimate science goal is the study of Ultra-High Energy Cosmic Rays (UHECR), the most energetic particles known in the Universe. Having macroscopic energies of over 10^20 eV, UHECRs are of yet unknown cosmic origin and are extremely rare. They penetrate our atmosphere at a rate of about one event per km2 and century, producing energetic atmospheric air showers, detectable through the ultraviolet fluorescence light they emit. The technique that our collaboration proposes for their detection consists of a spaceborne observatory, JEM-EUSO. Its objective is to monitor a very large volume of the Earth's nighttime atmosphere from above, recording a significant sample of ultraviolet light tracks initiated by UHECRs. In order to demonstrate the technologies and methods featured in the future space instrument, the EUSO-Balloon pathfinder has been developed by the JEM-EUSO collaboration. On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. From a float altitude of 38 km, the instrument operated during the entire astronomical night, observing UV-light from a variety of groundcovers and from hundreds of simulated air showers, produced by flashers and a laser during a two-hour helicopter under-flight. These results have been made possible by the restitution of the instruments attitude carried out at IRAP, i.e. an exhaustive analysis of the flight data from various attitude sensors on board of the balloon gondola. Also, a precise understanding of the Fresnel optics was required to analyze the data of the first EUSO-balloon flight. The all new optical system, integrated and tested at IRAP, has been characterized during two measurement campaigns. To test this large refractive system, a new test method has been developed. The optics performance, i.e. the efficiency and point spread function, came as something of a surprise, since none of the numerical models had predicted the observed behavior. These measurements are used in the analysis of the flight data and for the deep understanding of these brand-new Fresnel optics, key element in the design of the JEM-EUSO instrument.

The study presented in this thesis was motivated by the large uncertainty on the concentration of atmospheric electrical discharges to the global nitrogen budget. This uncertainty is partly due to the fact that information concerning the NOx production efficiency of electrical discharges having current signatures similar to those of lightning flashes is not available in the literature. Another reason for this uncertainty is the fact that energy is used as a figure of merit in evaluating NOx production from lightning flashes even though insufficient knowledge is available concerning the energy dissipation in lightning flashes. The third reason for this uncertainty is the lack of knowledge concerning the contribution of discharge processes other than return strokes to the NOx production in the atmosphere. Lightning is not the only process in the atmosphere that causes ionisation and dissociation of atmospheric air. Cosmic rays continuously bombard the Earth with high energetic particles and radiation causing ionization and dissociation of air leading to the production of NOx in the atmosphere. The work carried out in this thesis is an attempt to improve the current knowledge on the way in which these processes contribute to the global NOx production. Experiments have been conducted in this thesis to estimate the NOx production efficiency of streamer discharges, laser-induced plasma, laboratory sparks having current signatures similar to those of lightning flashes, alpha particle impact in air and finally with the lightning flash itself. The results obtained from laboratory electrical discharges show the following: (a) The NOx production efficiency, in terms of energy, of positive streamer discharges is more or less similar to those of hot discharges. (b) The NOx production efficiency of an electrical discharge depends not only on the energy but also on the peak and the shape of the current waveform. (c) The current signature is a better figure of merit in evaluating the NOx yield of electrical discharges. As a part of this thesis work a direct measurement of NOx generated by lightning flashes was conducted and the results show that slow discharge processes such as continuing currents could be the main source of NOx in lightning flashes. Concerning NOx production by other ionisation processes such as alpha particle impacts in the atmosphere, the data gathered in this thesis show that each ionising event in air leads to the creation of one NOx molecule. In terms of energy the NOx production efficiency of alpha particles is similar to that of electrical discharges. The theoretical studies conducted within this thesis indicate that M-components contribute more than the return strokes to the NOx production. The calculations also show that the contribution to the global NOx budget by return stroke is not as high as that assumed in the current literature.

Soil water content (SWC) measurements are crucial worldwide for hydrological predictions, agricultural activities, and monitoring the progress of reclamation on disturbed land from industrial activities. In colder climates, snow water equivalent (SWE) measurements are equally important, and directly contribute to improved spring water supply forecasting. Both these variables, SWC and SWE, are commonly measured with either point-scale (e.g. soil cores for SWC and snow tubes for SWE) or large-scale (remote sensing) methods. The cosmic-ray soil moisture probe (CRP) was recently developed to fill this gap between small- and large-scale measurements. The CRP provides an average SWC reading in a landscape-scale measurement footprint (300 m radius) by taking advantage of the relationship between aboveground neutrons and soil water. Although the CRP has proved accurate in relatively homogenous sites, it has not been validated at highly heterogeneous sites. Since snow is simply frozen water, the CRP also has the potential for monitoring SWE at the landscape-scale. However, no calibration has been developed for measuring SWE with the CRP. This thesis aimed to further validate the use of a CRP for measuring SWC at a highly heterogeneous site, and calibrate a CRP for monitoring landscape-scale SWE at an agriculture field. The heterogeneous site used to validate the CRP for SWC measurement was an oil sand reclamation site made up of multiple test plots of varying soil layer treatments. Despite the clear differences in soil texture at the site, the CRP-monitored SWC compared accurately to sampled soil water content and a network of soil moisture probes. With the use of modeling, it was also possible to downscale the CRP measurement to the plot scale. For calibrating the CRP for monitoring SWE, an empirical calibration function was developed based on the relationship between the CRP-measured neutrons and SWE from snow surveys with snow tubes. Using the calibration equation, CRP-estimated SWE closely matched SWE measured from snow surveys. Differences were attributed to mid winter and spring melting of the snowpack along with varying soil water content in the top of the soil profile. This research demonstrates the usefulness of the CRP for monitoring SWC at unique sites and its ability to monitor SWE at the landscape-scale.

The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free Fisk-Parker hybrid magnetic field model to demonstrate the behaviour of cosmic rays in the heliosphere due to such a field. This approach has been refined and the properties of the consequent field are investigated. It is found that randomly directed magnetic field diffusion in and above the photosphere significantly influences the solar magnetic field both at the solar poles and near the polar coronal hole boundary. The solar cycle dependence of this field is investigated, a study which is of particular importance for studies of the long-term behaviour of cosmic rays, such as those undertaken at the SANAE base in Antarctica. The amplitudes of the 26-day recurrent cosmic-ray variations are modelled as function of both latitudinal gradient and heliolatitude and are found to agree qualitatively and in some cases quantitatively with the observational results reported by Zhang 119971 and Paizis et al. 119991. Although magnetic field data do not clearly indicate the existence of the Fisk field [see, e.g., Fursyth et al., 20021, this study supports the existence of a Fisk-type HMF. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.

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.

The study of Supernova Remnants (SNRs) is fundamental to understanding the chemical enrichment and magnetism in galaxies, including our own Milky Way. In an effort to understand the connection between the morphology of SNRs and the Galactic Magnetic Field (GMF), we have examined the radio images of all known SNRs in our Galaxy and compiled a large sample that have an axisymmetric morphology, which we define to mean SNRs with a bilateral or barrel-shaped morphology, in addition to one-sided shells. We selected the cleanest examples and model each of these at their appropriate Galactic position using two GMF models, one of which includes a vertical halo component, and another that is oriented entirely parallel to the plane. Since the magnitude and relative orientation of the magnetic field changes with distance from the Sun, we analyze a range of distances, from 0.5 to 10 kpc in each case. Using a physically motivated model of an SNR expanding into an ambient GMF that includes a vertical halo component, we find it is possible to reproduce observed morphologies of many SNRs in our sample. These results strongly support the presence of an off-plane, vertical component to the GMF, and the importance of the Galactic field on SNR morphology. Our approach also provides a potentially new method for determining distances to SNRs, or conversely, distances to features in the large-scale GMF if SNR distances are known. The mechanism for acceleration of cosmic rays in SNRs is another outstanding question in the field. To investigate this, the same sample of axisymmetric SNRs was again modelled, but this time using two competing, and physically motivated, Cosmic Ray Electron (CRE) acceleration cases: quasi-perpendicular and quasi-parallel. We find that the quasi-perpendicular CRE acceleration case is much more consistent with the data than the quasi-parallel CRE acceleration case, with G327.6+14.6 (SN1006) being a notable exception. We propose that SN1006 may be an example of a case where both quasi-parallel and quasi-perpendicular acceleration is simultaneously at play in a single SNR. / October 2016

Nesta tese investigamos uma possível componente de partículas previstas por modelos além do modelo padrão da física de partículas, como por exemplo o massive gluino LSP, nos raios cósmicos de altíssimas energias (UHECR). Nosso objetivo é determinar os sinais experimentais em telescópios de fluorescência devidos a hádrons exóticos massivos e neutros, genericamente denominados de UHECRons. Para simular chuveiros iniciados por essa classe de partículas, alteramos o pacote Aires de simulação de chuveiros atmosféricos e o modelo hadrônico Sibyll. Estes chuveiros foram utilizados como entrada em simulações de telescópios de fluorescência por nós desenvolvidas, obtendo-se assim as distribuições dos observáveis desses chuveiros exóticos. A partir da comparação entre as características de chuveiros iniciados uhecrons e prótons, desenvolvemos métodos para a separação de sinais entre esses dois tipos de partículas. Esses métodos podem ser utilizados em uma análise inicial, com o intuito de procurar por sinais de partículas exóticas nos dados reais de observatórios de UHECR. / In this thesis we investigate a possible component of particles predicted by models beyond the standard model of particle physics, like the massive gluino LSP, in the ultra high energy cosmic rays (UHECR). Our objective is to determine the experimental signals on fluorescence telescopes due to exotic massive and neutral hadrons, generically called UHECRons. To simulate showers initiated by this class of particle, we altered the shower simulation package Aires and the hadronic model Sibyll. These showers were used as input in our simulations of fluorescence telescopes, thus obtaining the distribuitons of the observables for these exotic showers. By comparing the characteristics of showers initiated by uhecrons and protons, we developed methods to distinguish the signals between these two particles. These methods can be used in an initial analysis in order to look for signals of exotic particles in the real data of UHECR observatories.

[pt] O Observatório Pierre Auger é um detector de raios cósmicos ultra-energéticos (E maior ou igual 1018 eV) com características híbridas, que combinam detectores de superfície e de fluorescência. A determinação da composição química primária destes raios cósmicos é um dos seus principais objetivos. Há indícios de que os primários dos raios cósmicos com E maior que 1018.5 eV tem massa maior, conclusão baseada nos resultados recentes sobre a evolução dos chuveiros atmosféricos extensos (cascatas de partículas formadas quando da colisão do raio cósmico primário no topo da atmosfera com moléculas de N2 ou O2). Encontrar parâmetros, que caracterizam o chuveiro, no processo de sua reconstrução e que forneçam informações associadas a este resultado, são essenciais para validar esta conclusão. Nesta tese estuda-se a evolução como função da energia, de parâmetros que caracterizam os chuveiros, que sejam sensíveis à sua composição primária. Mais especificamente aqueles determinados pelo detector de superfície, pois há uma estatística de chuveiros detectados significativamente maior. Damos especial atenção às flutuações intrínsecas – chuveiro-a-chuveiro – do parâmetro de inclinação (beta) da Função de Distribuição Lateral, que descreve a variação da densidade de partículas ao longo da direção perpendicular ao eixo do chuveiro, como função da distância a esse eixo. Os resultados indicam que a flutuação intrínseca em beta, para eventos inclinados (45-60 graus) com E maior que 1018.5 eV, possui uma tendência de diminuição com a energia até valores em torno de 1019.8 eV. Este resultado é consistente com o encontrado anteriormente em análises de composição química sobre a evolução com a energia da profundidade de máximo (Xmax) dos chuveiros atmosféricos extensosmedida pelos detectores do Auger em modo híbrido, em que em energias acima de 1018.5 eV, observase que os chuveiros tendem a atingir seu máximo numa região mais bem definida da atmosfera, levando, por conseguinte, a flutuações menores no sinal no solo. / [en] The Pierre Auger Observatory is an ultra high energy cosmic ray detector (E more than or equal as 1018 eV) which has hybrid characteristics combining surface and fluorescence detectors. Determining the cosmic rays chemical composition is one of its most important challenges. There are evidences that cosmic ray primaries with energy above 1018.5 eV are heavy and this conclusion is based on recent results on the evolution of extensive air showers (cascades of particles formed by the collision of primary cosmic rays in the top of the atmosphere with nitrogen and oxygen molecules). Therefore, it is mandatory to find additional parameters supporting that conclusion. In this thesis, the evolution with energy of parameters characterizing the shower and with sensitivity to chemical composition are studied. More specifically, parameters determined by the surface detector are analyzed due to the high statistics in this operation mode. Special attention is given to the instrinsic - shower to shower - fluctuations of the slope parameter (beta) of the Lateral Distribution Function which describes the particles density variation in the plane perpendicular to the shower axis as a function of distance to that axis. The results show that the intrinsic fluctuation of Beta, for inclined showers (45-60 degrees) with energy above 1018.5 eV, where the detector resolution is small compared to the total fluctuation, has a trend to decrease with energy up to 1019.6 eV. This result is consistent with recent results on the energy evolution of the depth of shower maxima (Xmax) of extensive air showers, where above 1018.5 eV, the distributions of Xmax show less fluctuations, leading, in turn, to less fluctuations on the ground level.

This work aims to contribute to the study of the origins of cosmic rays, and broadly, to the advancement of both data analysis methods and instrumentation for very-high-energy γ-ray astronomy. First, reviewing the state of γ-ray astronomy, we show how gains in sensitivity can be achieved through sophisticated data analyses and improved instrumental designs. We then develop such an improved analysis method for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) by combining Image Template Method (ITM) with Boosted Decision Trees (BDT), and study its performance, attaining a 30-50% improvement in integral sensitivity over the instrument’s standard analysis. Systematic issues in spectral reconstruction that the analysis displays are resolved satisfactorily by imposing a more stringent condition on the selection of its energy threshold. We employ the newly developed analysis to measure the γ-ray energy spectrum of the starburst galaxy M82, and combining our result with a measurement from the Fermi Large Area Telescope (Fermi-LAT), we find that a single power law fits the spectrum well between 100 GeV and 10 TeV, with no evidence for a spectral break or a cutoff. We conclude that this is in line with the current understanding that M82 is not a good proton calorimeter. Finally, we detail the design, implementation, and performance of the optical alignment system of the prototypeSchwarzschild-Couder Telescope (pSCT) for the Cherenkov Telescope Array (CTA), a novel two-mirror design that addresses many shortcomings of current instruments.