The transport of cosmic rays in the heliosphere is studied by making use of a newly developed modulation model. This model employes stochastic differential equations to numerically solve the relevant transport equation, making use of this approach’s numerical advantages as well as the opportunity to extract additional information regarding cosmic ray transport and the processes responsible for it. The propagation times and energy losses of galactic electrons and protons are calculated for different drift cycles. It is confirmed that protons and electrons lose the same amount of rigidity when they experience the same transport processes. These particles spend more time in the heliosphere, and also lose more energy, in the drift cycle where they drift towards Earth mainly along the heliospheric current sheet. The propagation times of galactic protons from the heliopause to Earth are calculated for increasing heliospheric tilt angles and it is found that current sheet drift becomes less effective with increasing solar activity. Comparing calculated propagation times of Jovian electrons with observations, the transport parameters are constrained to find that 50% of 6 MeV electrons measured at Earth are of Jovian origin. Charge-sign dependent modulation is modelled by simulating the proton to anti-proton ratio at Earth and comparing the results to recent PAMELA observations. A hybrid cosmic ray modulation model is constructed by coupling the numerical modulation model to the heliospheric environment as simulated by a magneto-hydrodynamic model. Using this model, it is shown that cosmic ray modulation persists beyond the heliopause. The level of modulation in this region is found to exhibit solar cycle related changes and, more importantly, is independent of the magnitude of the individual diffusion coefficients, but is rather determined by the ratio of parallel to perpendicular diffusion. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2013

Big Bang Nucleosynthesis (BBN), together with the analyses of the Cosmic Microwave Background (CMB) anisotropies, confirm what our day to day experience of life attests :antimatter is far less present than matter in the Universe. In addition, these observables also permit to evaluate that there exists about one proton for every 10^{10} photons present in the Universe. This is in contradiction with expectations coming from the standard hot big bang, where no distinction between matter and antimatter is made, and where subsequent annihilations would lead to equal matter and antimatter contents, at a level 10^{−10} smaller than the observed one. The Standard Model of fundamental interactions fails to explain this result, leading us to search for ‘Beyond the Standard Model’ physics.<p><p>Among the possible mechanism which could be responsible for the creation of such a matter asymmetry, leptogenesis is particularly attractive because it only relies on the same ingredients previously introduced to generate neutrino masses. Unfortunatelly, this elegant proposal suffers from a major difficulty :it resists to any tentative of being probed by our low energy observables. In this thesis, we tackle the problem the other way around and propose a way to falsify this mechanism. Considering the type-I leptogenesis mechanism, i.e. a mechanism based on the asymmetric decay of right-handed neutrinos, in a left-right symmetric framework, we show that the observation of a right-handed gauge boson W_R at future colliders would rule out any possibility for such mechanism to be responsible of the matter asymmetry present in our Universe.<p><p>Another intriguing question that analyses of the anisotropies of the CMB confirmed is the presence of a non-baryonic component of matter in our Universe, i.e. the dark matter. As hinted by observations of galactic rotation curves, it should copiously be present in our galactic halo, but is notoriously difficult to detect directly. We can take advantage on the fact that antimatter almost disappeared from our surroundings to detect the contamination of cosmic rays from standard sources the annihilation products of dark matter would produce.<p><p>The second subject tackled in this work is the study of the imprints the Inert Doublet Modem (IDM) could leave in (charged) cosmic rays, namely positrons, antprotons and antideuterons. This model, first proposed to allow the Bout-Englert-Higgs particle to evade the Electroweak Precision Test (EWPT) measurements, introduces an additional scalar doublet which is inert in the sense that it does not couple directly to fermions. This latter property brings an additional virtue to this additional doublet :since it interacts weakly with particles, it can play the role of dark matter. This study will be done in the light of the data recently released by the PAMELA, ATIC and Fermi-GLAST collaborations, which reported e^± excesses in two different energy ranges. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

My disertation theses explores the intricate relationship between art, science and photography in the framework of the contemporary culture. Clearly outlined research areas open up the subject to a broader theoretical examination to underpin the artistic strategies that can be employed in the practial research. The resulting artwork interprets the domain of particle physics in a series of artworks. First area of the research delves into the domain of images and seeks to understand the relationship between the images of art and science in a broader sense. Second area investigates ambiguous medium of photography as both tool of science and art. Third area is an overview of the history of representation of the subatomic world and issues related to representing what is in fact unrepresentable. Fourth seeks to find epistemic and conceptual connection between art and science and their interdisciplinary dialogue as Sci-Art. The fifth part introduces artworks that reflect the critical egangement with the theoretical research and the scientific method by building the instrument for the observation of the cosmic rays. Sources for the theoretical framework are largely drawn from the academic literature written in the UK and USA where the topics explored in the theses have been studied in depth. The time scope considered in the theses encompasses 1990's of the 20. century up utill the present day.

<p>У докторској дисертацији&nbsp; приказани су резултати развијених и примењених коинцидентних метода за временску анализу нуклеарних процеса. Експериментални коинцидентни системи засновани су на&nbsp; HPGe&nbsp; и пластичним сцинтилационим детекторима.&nbsp; Извршена су три експеримента, која су показала примењивост развијених коинцидентних система. Први део експерименталног дела обухвата анализе временских варијација интензитета космичког зрачења посредством нискоенергијских фотона. Показано је да се праћењем интензитета нискоенергијских фотона у току времена у различитим енергијским регионима остварује бољи увид у анализу фонских догађаја, стварајући предуслове за извођење експеримената који трагају за ретким нуклеарним процесима. Поред праћења временских варијација интензитета, метода се може применити и&nbsp; на детекцију периодичних и апериодичних догађаја повезаних са активношћу Сунца. Други део дисертације обухватао је истраживања везана&nbsp; за&nbsp; детекцију потенцијалних&nbsp; флуктуација константе распада 22 Na. Развијен је коинцидентни систем&nbsp; и&nbsp; у току времена је&nbsp; праћен интензитет анихилационе линије, која је резултат анихилације позитрона емитованог распадом 22Na.&nbsp; За време трајања&nbsp; аквизиције података, нису пронађена значајна одступања испитиване константе распада од стандардног експоненцијалног закона радиоактивног распада. У трећем делу експерименталног рада, приказана је коинцидентна метода за временско раздвајање догађаја индукованих мионима и неутронима у околини детекторског система. Добијена је временска крива у експерименту и извршена је детаљна анализа различитих временских региона. Извршене су Монте Карло симулације, на основу којих је добијена временска крива. Анализом различитих региона симулиране временске криве, показано је да се ови догађаји могу раздвојити у две велике групе&ndash;брзе и споре догађаје. Међу спорим догађајима, показано је да се може направити разлика између догађаја индукованих мионима, међу којима доминира анихилација, и догађаја индукованих неутронима, који спадају у закаснеле догађаје у групи спорих догађаја. Добијено је да неутрони највише доприносе нискоенергијском региону, првенствено у региону до&nbsp; &asymp;50&nbsp; keV,&nbsp; што их чини&nbsp; нежељеном кариком фонских догађаја у експериментима који трагају за ретким нуклеарним догађајима. На основу резултата симулација, анализирани су електромагнетни и хадронски процеси индуковани мионима и неутронима, као и удели мионске и неутронске компоненте у коинцидентном спектру HPGe&nbsp; детектора и директном спектру пластичног сцинтилационог детектора. Закључено је да нискоенергијском спектру,&nbsp; који је превасходно значајан за ретке нуклеарне процесе,&nbsp; доминантно доприносе неутрони.</p> / <p>U doktorskoj disertaciji&nbsp; prikazani su rezultati razvijenih i primenjenih koincidentnih metoda za vremensku analizu nuklearnih procesa. Eksperimentalni koincidentni sistemi zasnovani su na&nbsp; HPGe&nbsp; i plastičnim scintilacionim detektorima.&nbsp; Izvršena su tri eksperimenta, koja su pokazala primenjivost razvijenih koincidentnih sistema. Prvi deo eksperimentalnog dela obuhvata analize vremenskih varijacija intenziteta kosmičkog zračenja posredstvom niskoenergijskih fotona. Pokazano je da se praćenjem intenziteta niskoenergijskih fotona u toku vremena u različitim energijskim regionima ostvaruje bolji uvid u analizu fonskih događaja, stvarajući preduslove za izvođenje eksperimenata koji tragaju za retkim nuklearnim procesima. Pored praćenja vremenskih varijacija intenziteta, metoda se može primeniti i&nbsp; na detekciju periodičnih i aperiodičnih događaja povezanih sa aktivnošću Sunca. Drugi deo disertacije obuhvatao je istraživanja vezana&nbsp; za&nbsp; detekciju potencijalnih&nbsp; fluktuacija konstante raspada 22 Na. Razvijen je koincidentni sistem&nbsp; i&nbsp; u toku vremena je&nbsp; praćen intenzitet anihilacione linije, koja je rezultat anihilacije pozitrona emitovanog raspadom 22Na.&nbsp; Za vreme trajanja&nbsp; akvizicije podataka, nisu pronađena značajna odstupanja ispitivane konstante raspada od standardnog eksponencijalnog zakona radioaktivnog raspada. U trećem delu eksperimentalnog rada, prikazana je koincidentna metoda za vremensko razdvajanje događaja indukovanih mionima i neutronima u okolini detektorskog sistema. Dobijena je vremenska kriva u eksperimentu i izvršena je detaljna analiza različitih vremenskih regiona. Izvršene su Monte Karlo simulacije, na osnovu kojih je dobijena vremenska kriva. Analizom različitih regiona simulirane vremenske krive, pokazano je da se ovi događaji mogu razdvojiti u dve velike grupe&ndash;brze i spore događaje. Među sporim događajima, pokazano je da se može napraviti razlika između događaja indukovanih mionima, među kojima dominira anihilacija, i događaja indukovanih neutronima, koji spadaju u zakasnele događaje u grupi sporih događaja. Dobijeno je da neutroni najviše doprinose niskoenergijskom regionu, prvenstveno u regionu do&nbsp; &asymp;50&nbsp; keV,&nbsp; što ih čini&nbsp; neželjenom karikom fonskih događaja u eksperimentima koji tragaju za retkim nuklearnim događajima. Na osnovu rezultata simulacija, analizirani su elektromagnetni i hadronski procesi indukovani mionima i neutronima, kao i udeli mionske i neutronske komponente u koincidentnom spektru HPGe&nbsp; detektora i direktnom spektru plastičnog scintilacionog detektora. Zaključeno je da niskoenergijskom spektru,&nbsp; koji je prevashodno značajan za retke nuklearne procese,&nbsp; dominantno doprinose neutroni.</p> / <p>In&nbsp; this&nbsp; doctoral&nbsp; thesis,&nbsp; the&nbsp; results&nbsp; of&nbsp; the&nbsp; developed and&nbsp; applied&nbsp; coincidence&nbsp;&nbsp; methods&nbsp; on&nbsp; the&nbsp; timeanalysis&nbsp; of&nbsp; nuclear&nbsp; processes&nbsp; are&nbsp; presented. Coincidence systems, used in presented experiments, are&nbsp; based&nbsp; on&nbsp; the&nbsp; HPGe&nbsp; and&nbsp; plastic&nbsp; scintillation detectors.&nbsp; Three&nbsp; experiments&nbsp; were&nbsp; performed,showing&nbsp; a&nbsp; wide&nbsp; application&nbsp; of&nbsp; the&nbsp; developed coincidence&nbsp; systems.&nbsp; The&nbsp; first&nbsp; part&nbsp; of&nbsp; the experimental work involves the analysis of the time&nbsp; variations of cosmic rays via low-energy photons. It was&nbsp; shown&nbsp; that&nbsp; by&nbsp; analyzing&nbsp; the&nbsp; intensity&nbsp; of&nbsp; lowenergy photons better insight into the behavior of thebackground&nbsp; events&nbsp; is&nbsp; provided,&nbsp; which&nbsp; is&nbsp;&nbsp; especially important&nbsp; as&nbsp; a&nbsp; precondition&nbsp; for&nbsp; rare&nbsp; nuclear&nbsp; events experiments.&nbsp; Furthermore,&nbsp; it&nbsp; was&nbsp; shown&nbsp; that&nbsp; this method can be applied in order to search for periodic or aperiodic events resulting from the Sun activity. The&nbsp; second&nbsp; part&nbsp; contains&nbsp; the&nbsp; research&nbsp; of&nbsp; the&nbsp; 22Na decay constant fluctuations. The coincidence system was&nbsp; developed&nbsp; and&nbsp; the&nbsp; intensity&nbsp; of&nbsp; the&nbsp; annihilation line,&nbsp; resulting&nbsp; from&nbsp; annihilation&nbsp; of&nbsp; the&nbsp; positrons emitted from 22Na, was followed with time. During&nbsp; he&nbsp; acquisition&nbsp; time,&nbsp; no&nbsp; significant&nbsp; deviations&nbsp; from the standard exponential radioactive decay law were found. In&nbsp; the&nbsp; third&nbsp; part&nbsp; of&nbsp; the&nbsp; experimental&nbsp; work,&nbsp; the coincidence&nbsp; method&nbsp; for&nbsp; time&nbsp; separation&nbsp; of&nbsp; the events,&nbsp; induced&nbsp; by&nbsp; cosmic&nbsp; muons&nbsp; and&nbsp; neutrons&nbsp; in the&nbsp; vicinity&nbsp; of&nbsp; the&nbsp; detectors&nbsp; system,&nbsp; was&nbsp; presented. The time curve was obtained in the experiment and the&nbsp; detailed&nbsp; analysis&nbsp; of&nbsp; the&nbsp; different&nbsp; time&nbsp; regions was&nbsp; performed.&nbsp; The&nbsp; Monte&nbsp; Carlo&nbsp; simulations&nbsp; were conducted&nbsp; and&nbsp; the&nbsp; time&nbsp; curve&nbsp; from&nbsp; the&nbsp; simulation results was obtained. Analyzing the different regions of the simulated time curve, it was noticed that these events can be separated into two groups&ndash;prompt and delayed.&nbsp; Between&nbsp; delayed&nbsp; events,&nbsp; it&nbsp; was&nbsp; concluded that&nbsp; events&nbsp; induced&nbsp; by&nbsp; muons,&nbsp; dominantly annihilation&nbsp; line,&nbsp; and&nbsp; events&nbsp; induced&nbsp; by&nbsp; neutrons, which&nbsp; may&nbsp; be&nbsp; classified&nbsp; as&nbsp; more&nbsp; delayed&nbsp; events&nbsp; in the&nbsp; group&nbsp; of&nbsp; the&nbsp; delayed&nbsp; events,&nbsp; can&nbsp; be distinguished.&nbsp; It&nbsp; was&nbsp; concluded&nbsp; the&nbsp; neutrons dominantly&nbsp; contribute&nbsp; to&nbsp; the&nbsp; low-energy&nbsp; region, mostly&nbsp; in&nbsp; the&nbsp; region&nbsp; to&nbsp; &asymp;50&nbsp; keV,&nbsp; which&nbsp; makes neutrons&nbsp; an&nbsp; important&nbsp; background&nbsp; in&nbsp; the experiments searching for rare nuclear events. Based on&nbsp; the&nbsp; simulation&nbsp; results,&nbsp; electromagnetic&nbsp; and hadronic processes induced by muons and neutrons, as&nbsp; well&nbsp; as&nbsp; portions&nbsp; of&nbsp; muon&rsquo;s&nbsp; and&nbsp; neutron&rsquo;s component&nbsp; in&nbsp; the&nbsp; coincidence&nbsp; spectrum&nbsp; of&nbsp; HPGe detector&nbsp; and&nbsp; direct&nbsp; spectrum&nbsp; of&nbsp; the&nbsp; plastic scintillation&nbsp; detector&nbsp; were&nbsp; analyzed.&nbsp; It&nbsp; was concluded&nbsp; that&nbsp; in&nbsp; the&nbsp; low-energy&nbsp; part&nbsp; of&nbsp; the spectrum,&nbsp; primarily important for the search for rare nuclear&nbsp; events,&nbsp; dominant&nbsp; influence&nbsp; is&nbsp; originated from cosmic neutrons.</p>