Cette thèse expérimentale est consacrée à l’optimisation d’une source de rayons X Kalpha générée par interaction laser femtoseconde à fort contraste temporel avec une cible épaisse en molybdène. Ce travail vise à explorer l’effet du contraste temporel sur l’émission Kalpha sur une gamme d’intensité combinant les deux régimes relativiste et non-relativiste. La première étude est consacrée à l’évolution de l’émission Kalpha en fonction du contraste temporel et de l’intensité. L’étude a révélé différents comportements de l’émission Kalpha suivant la valeur du contraste et d’intensité. L’étude a aussi montré une émission Kalpha indépendante du contraste dans le régime relativiste. Au regard des travaux de la littérature, nous avons proposé une première interprétation des résultats obtenus. Il s’agit d’établir un lien entre l’émission Kalpha et les mécanismes d’absorption de l’énergie laser. Certains mécanismes sont dépendants de l’angle d’incidence. Afin d’appuyer notre interprétation, une deuxième étude du rendement de la source Kalpha en fonction de l’angle d’incidence a été réalisée. Ainsi les résultats obtenus sont en accord avec certaines de nos conclusions. En outre, Nous nous sommes intéressés à l’effet de l’étirement temporel de l’impulsion. Nous avons observé une sensibilité de l’émission suivant le signe du chirp. Enfin, nous avons étudié l’effet du contraste et de l’intensité sur la taille de la source X. Celle-ci est d’autant plus réduite que le contraste est plus fort et devient très proche de la tache focale laser à faible intensité laser. Le rendement de production en photon Kalpha atteint est de 2 × 10^−4, similaire au meilleur rendement reporté à ce jour. / This thesis is focused on the optimization of a Kalpha x-ray source induced by high contrast femtosecond laser molybdenum thick target interaction. The objective of this work is to explore the effect of the temporal contrast ratio on Kalpha emission in an intensity range including the non relativistic and relativistic regimes. The first study consists of the measurement of Kalpha emission as a function of contrast ratio and intensity. The study shows different behaviors of the emission depending on the contrast ratio and intensity range. Furthermore, it was found that in the relativistic regime Kalpha production is independant of the contrast ratio. According to published work in litterature, we proposed a first intepretation of the obtained results. In particular, we discuss the absorption mechanism of laser pulse energy for each contrast ratio and intensity condition. Some of the mechanisms are dependant on the angle of incidence of the pulse on target. Thus, to verify the validity of our interpretation, we study the Kalpha effciency as a function of the angle of incidence. Most of the results agree with our first conclusions. Furthermore, we investigate the effect of the chirped pulse of the Kalpha emission. It is shown that Kalpha emission is sensitive to the sign of the chirp. Finally, we performed a study on the effect of contrast ratio and intensity on the x-ray source size. It was observed that high contrast ratio decreases strongly the x-ray source size which aproaches the focal spot size at low laser intensity. High Kalpha efficiency is reached 2 × 10^−4 which is similar to the highest effciency reported to date in litterature for a thick molybdenum target.

Les étoiles à neutrons sont parmi les objets les plus extrêmes dans l'univers. Elles sont des étoiles compactes, nées à la suite d'une explosion de supernova gravitationnelle, au point final de l'évolution stellaire. Le champ gravitationnel y est très fort, et la matière à l'intérieur atteint des densités extrêmement élevées. Elles sont donc des "laboratoires" prometteurs, non seulement pour tester le régime de champ fort en relativité générale, mais aussi pour en apprendre davantage sur la physique nucléaire à haute densité, qui actuellement ne peut pas être reproduit avec des expériences terrestres. Ainsi, les étoiles à neutrons nous permettent d'adresser des questions telles que l'existence éventuelle de particules autres que nucléons à haute-densité. À cause de la naissance violente de ces objets, les étoiles à neutrons très jeunes, que l'on appelle proto-étoiles à neutrons, sont également très chaudes, et souvent en rotation différentielle rapide. Dans cette thèse nous avons pour but de développer un modèle stationnaire d'une telle proto-étoile à neutrons.Ainsi, nous présentons une nouvelle méthode pour calculer numériquement les équations d'équilibre d'un fluide parfait relativiste, axisymétrique et stationnaire, en rotation différentielle et à température finie, valable pour une équation d'état réaliste. Nous présentons en détail le code (accessible au public) développé. Nous avons appliqué ce code avec des nouvelles équations d'état réalistes à température finie, basée sur une théorie relativiste du champ moyen, en incluant tous les degrés de liberté hyperoniques. Nous avons calculé des modèles relativistes stationnaires de proto-étoiles à neutrons en rotation différentielle rapide. Nous allons discuter les applications de nos modèles pour explorer plus en détail la physique de ces objets. / Neutron stars are among the most extreme objects in the universe. They are compact stars born as the aftermath of a core-collapse supernova explosion, at the endpoint of stellar evolution, with a strong gravitational field, and extremely high densities. They are therefore promising 'laboratories', not only to test the strong-field regime of general relativity, but also to learn about nuclear physics in the high density regime, which presently is not accessible in earth based experiments. This allows to address questions such as the possible existence of particles other than nucleons at high-densities. As a consequence of the violent birth of these objects, new-born (proto-)neutron stars are extremely hot and, in general, rapidly rotating, which raises interesting problems in the task of developing a stationary model of such objects.In this thesis, we present a new self-consistent method to numerically compute the equilibrium equations of stationary axisymmetric relativistic (differentially) rotating perfect fluids at finite temperature, with a realistic equation of state. We introduce in detail the (publicly available) code in which we implemented the described numerical scheme. We use newly developed realistic equations of state with finite temperature, which are based on density dependent relativistic mean field theory, and in which all hyperonic degrees of freedom are included, to compute realistic stationary relativistic models of rapidly differentially rotating proto-neutron stars. We discuss future applications of our code for further exploring the physics of proto-neutron stars.

Dans les tokamaks, Sous l'application champ de électrique, les électrons sont accélérés et en même temps, ils subissent une force de friction due aux collisions avec les autres particules du plasma. Cependant, une fraction de la population totale d'électrons peuvent surmonter la force de friction et atteindre une vitesse proche de la vitesse lumière. Ces électrons relativistes sont découplés du plasma et sont appelés électrons runaway (ER). Ils peuvent apparaître lors des différentes phases d'une décharge de plasma. Par exemple, dans la phase de démarrage ou alors pendant les disruptions, au cours desquelles une fraction importante du courant plasma peut être convertie en ER ayant une énergie pouvant atteindre quelques dizaines de MeV. Les ER créés pendant la phase de perturbation peuvent causer des dommages aux premiers composants murs si un dépôt localisé de forte puissance se produit. ITER étant un tokamak de grande taille et un projet coûteux, la génération d'ER n'est pas souhaitable. La viabilité de la machine nécessite que les ER soient détectés en temps réel. La thèse fournit une étude détaillée dans cette direction pour le développement des deux principaux diagnostics sur ITER impliqués dans les mesures de paramètres pour les ER, à savoir, le moniteur de rayons X durs qui détecte le rayonnement de bremsstrahlung et les caméras visibles et infrarouges qui détectent le rayonnement synchrotron. Une solution de conception unique a été proposée pour le moniteur HXRM et est développée ici et optimisée. Pour les caméras, une modélisation des signaux est effectuée pour la première fois. Pour ce faire, un code de calcul a été développé et validé sur différents tokamaks. / In tokamaks, under the application of the electric field, a small fraction of the total electrons population can overcome collisional drag force and attain high velocity close to the speed of light. These relativistic electrons are called Runaway-Electrons (REs). The REs can occur during different phases of a plasma discharge. REs created during the disruptions phase can form a high energetic RE-beam that poses a risk to damage the first wall components if localized high power deposition takes place. ITER being a large size tokamak and an expensive project, generation of REs is not desirable during any phases of a plasma discharge. Detection of these REs and measurements of its parameters are important for the tokamak operation. Hence, RE diagnostics have to be in place to aid the commissioning of the disruption mitigation system and also for the post-event analysis to improve the reliability of RE avoidance. The present thesis gives a detailed study in this direction for the development of the two principal ITER Diagnostics involved in RE parameter measurements, namely the Hard X-Ray Monitor (HXRM) that detects bremsstrahlung radiation and the Visible and Infrared Cameras that detect synchrotron radiation. A unique design solution has been given for the HXRM and is developed, R&D tests were performed and optimized in line with this understanding. For the cameras, it is predicted for the first time which images and signal intensity can be expected. To achieve this, a simple but comprehensive code has been developed and validated on tokamaks that can predict RE parameters and corresponding diagnostic signals which may have further uses also in the context of RE avoidance.

This thesis concerns quadratic response properties and their application to properties in Jablonski diagrams such as resonant two-photon absorption and excited state absorption. Our main interest lies in optical power limiting applications, and in this context, molecules containing heavy metal atoms prove superior. Therefore, we are interested in how relativity affects these properties, and in order to assess this, a four-component relativistic framework is adopted. To properly address the molecular properties of interest, both relativistic effects and electron correlation need to be accounted for. These two properties are not additive, and, therefore, correlation needs to be incorporated into the four-component framework. We present the implementation of quadratic response properties at the four-component density functional level of theory. For second-harmonic generation, we have, with numerical examples, demonstrated that correlation and relativity are indeed not additive and that the inclusion of noncollinear magnetization is of little importance. We report that both electron correlation as well as relativity strongly affect results for second-harmonic generation. For example, relativity alone reduces the µβ-response signal by 62% and 75% for meta- and ortho-bromobenzene, respectively, and enhances the same response by 17% and 21% for meta- and ortho-iodobenzene, respectively. In the four-component framework, we present the implementations of single and double residues of the quadratic response function, which allows for the evaluation of resonant two-photon absorption cross sections and excited state properties. Using these tools, we discuss different levels of approximation to the relativistic Hamiltonian and we demonstrate that for two-photon absorption, a proper treatment of relativistic effects qualitatively alters the spectrum. For example, already for an element as light as neon, significant differences are seen between the relativistic and nonrelativistic spectra as triplet transitions acquire substantial absorption cross sections in the former case. Finally, quantum mechanics in conjunction with electrodynamics is applied to determine clamping levels in macroscopic samples. The microscopic properties of the optically active chromophores are determined by response theory, and then, electrodynamics is used to describe the interactions between the chromophores and incident laser pulses. Using this approach a series of molecules have been investigated and their performances have been compared and ranked in order to find novel materials for optical power limiting applications.

Spin-orbit coupling (SOC) reduces the spatial symmetry of ferromagnetic solids. That is, the physical properties of ferromagnetic materials are anisotropic, depending on the magnetization direction. In this thesis, by means of numerical calculations with full-relativistic density functional theory, we studied two kinds of physical properties: surface magnetic anisotropy energy (MAE) and anisotropic thermoelectric power due to Lifshitz transitions. After a short introduction to the full-relativistic density functional theory in Chapter 2, the MAE of ferromagnetic thin films is studied in Chapter 3. For such systems, separation of different contributions, such as bulk magnetocrystalline anisotropy (MCA) energy, shape anisotropy energy, and surface/interface anisotropy energy, is crucial to gain better understanding of experiments. By fitting our calculating results for thick slabs to a phenomenological model, reliable surface MAE could be obtained. Following this idea, we have studied the MAE of Co slabs with different geometries, focusing on the effects of orbital polarization correction (OPC). We found that the surface anisotropy is mainly determined by the geometry. While OPC gives better results of orbital moments, it overestimates the MAE. In the second part of Chapter3, the effects of electric fields on the MAE of L10 ferromagnetic thin films are studied. Using a simple model to simulate the electric field, our calculations are in good agreement with previous experimental results. We predicted that for CoPt, even larger effects exist. Moreover, we found that it is the amount of screening charge that determines the magnetoelectric coupling effects. This gives us some clue about how to achieve electric field control of magnetization direction. In Chapter 4, Lifshitz transitions in L10 FePt caused by a canted magnetic field are studied. We found several Lifshitz transitions in ordered FePt with tiny features in DOS. Using a two-band model, it is demonstrated that at such transitions, the singular behaviour of kinetic properties is due to the interband scattering, and the singularity itself is proportional to the derivative of the singular DOS. For FePt, such singularity will be smeared into anomaly by chemical disorder. Using CPA, we studied the effects of energy level broadening for the critical bands in FePt. We found that for experimentally available FePt thin films, Lifshitz transitions would induce up to a 3% increase of thermopower as the magnetization is rotated from the easy axis to the hard axis. / Spin-Bahn-Kopplung reduziert die Symmetrie ferromagnetischer Festkörper. Das bedeutet, dass die physikalischen Eigenschaften ferromagnetischer Stoffe anisotrop bezüglich der Magnetisierungsrichtung sind. In dieser Dissertation werden mittels numerischer voll-relativistischer Dichtefunktional-Rechnungen zwei Arten physikalischer Eigenschaften untersucht: magnetische Oberflächen-Anisotropieenergie (MAE) und anisotrope Thermokraft durch Lifshitz-Übergänge. Nach einer kurzen Einführung in die relativistische Dichtefunktional-Theorie in Kapitel 2 wird in Kapitel 3 die MAE ferromagnetischer dünner Filme untersucht. In diesen Systemen ist es für ein Verständnis experimenteller Ergebnisse wichtig, verschiedene Beiträge zu separieren: Volumenanteil der magnetokristallinen Anisotropie (MCA), Formanistropie und Oberflächen bzw. Grenzflächenanisotropie. Durch Anpassen berechneter Daten für dicke Schichten an ein phänomenologisches Modell konnten verlässliche Oberflächen Anisotropien erhalten werden. In dieser Weise wurde die MAE von Co- Schichten mit unterschiedlichen Geometrien untersucht, wobei der Einfluss von Orbitalpolarisations-Korrekturen (OPC) im Vordergrund stand. Es wurde gefunden, dass die Oberflächenanisotropie hauptsächlich von der Geometrie bestimmt wird. Während OPC bessere Ergebnisse für die Orbitalmomente liefert, wird die MAE überschätzt. Im zweiten Teil von Kapitel 3 wird der Einfluss elektrischer Felder auf die MAE von dünnen ferromagnetischen Filmen mit L10-Struktur untersucht. Unter Verwendung eines einfachen Modells zur Simulation des elektrischen Feldes liefern die Rechnungen gute Übereinstimmung mit vorliegenden experimentellen Ergebnissen. Es wird vorhergesagt, dass für CoPt ein noch größerer Effekt existiert. Weiterhin wurde gefunden, dass die magnetoelektrische Kopplung von der Größe der Abschirmladung bestimmt wird. Dies ist eine wichtige Einsicht, um die Magnetisierungsrichtung durch ein elektrisches Feld kontrollieren zu können. In Kapitel 4 werden Lifshitz-Übergänge untersucht, die ein gekantetes Magnetfeld hervorruft. Es wurden mehrere Lifshitz-Übergänge in geordnetem FePt gefunden, welche kleine Anomalien in der Zustandsdichte hervorrufen. Mit Hilfe eines Zweiband-Modells wird gezeigt, dass an solchen Übergängen das singuläre Verhalten kinetischer Eigenschaften durch Interband- Streuung verursacht wird und dass die Singularität proportional zur Ableitung der singulären Zustandsdichte ist. In FePt wird durch chemische Unordnung diese Singularität zu einer Anomalie verschmiert. Der Einfluss einer Verbreiterung der Energieniveaus der kritischen Bänder in FePt wurde mittels CPA untersucht. Es wurde gefunden, dass in experimentell verfügbaren dünnen FePt-Filmen Lifshitz-Übergänge bis zu 3% Erhöhung der Thermokraft erzeugen, wenn die Magnetisierung von der leichten in die harte Richtung gedreht wird.

We study point particles to illustrate the various symmetries such as the Poincaré group and its non-relativistic version. In order to find the Noether charges and the Noether currents, which are conserved under physical symmetries, we study Noether’s theorem. We describe the Pauli-Lubanski spin vector, which is invariant under the Poincaré group and describes the spin of a particle in field theory. By promoting the Pauli-Lubanski spin vector to an operator in the quantized theory we will see that it describes the spin of a particle. Moreover, we find an action for a smooth spinning bosonic particle by compactifying one string dimension together with one embedding dimension. As with the Pauli-Lubanski spin vector, we need to quantize this action to confirm that it is the action for a smooth spinning particle. / Vi studerar punktpartiklar för att illustrera olika symemtrier som t.ex. Poincaré gruppen och dess icke-relativistiska version. För att hitta de Noether laddningar och Noether strömmar, vilka är bevarade under symmetrier, studerar vi Noether’s sats. Vi beskriver Pauli-Lubanksi spin vektorn, vilken har en invarians under Poincaré gruppen och beskriver spin hos en partikel i fältteori. Genom att låta Pauli-Lubanski spin vektorn agera på ett tillstånd i kvantfältteori ser vi att den beskriver spin hos en partikel. Dessutom finner vi en verkan för en spinnande partikel genom att kompaktifiera en bosonisk sträng dimension tillsammans med en inbäddad dimension. Som med Pauli-Lubanski spin vektorn, kvantiserar vi denna verkan för att bekräfta att det är en verkan för en spinnande partikel.

Στην παρούσα διατριβή υπολογίζονται σχετικιστικά πολυτροπικά μοντέλα περιστρεφομένων αστέρων νετρονίων, καθώς και μοντέλα που περιγράφονται από ρεαλιστικές καταστατικές εξισώσεις. Σκοπός αυτής της μελέτης είναι να υπολογιστούν σημαντικές φυσικές ποσότητες ενός αστέρα νετρονίων, στην περίπτωση της υδροστατικής ισορροπίας, της ομοιόμορφης αλλά και της διαφορικής περιστροφής, καθώς και στην περίπτωση που ο αστέρας έχει μαγνητικό πεδίο με πολοειδή και τοροειδή συνιστώσα. Μία σύντομη περιγραφή της αριθμητικής διαπραγμάτευσης έχει ως εξής. Καταρχάς, επιλύεται το σύστημα διαφορικών εξισώσεων Oppenheimer-Volkov (OV). Το σύστημα αυτό περιγράφει την υδροστατική ισορροπία μη περιστρεφομένων πολυτροπικών μοντέλων. Στη συνέχεια, θεωρείται η ομοιόμορφη περιστροφή ως διαταραχή, σύμφωνα με την «μέθοδο διαταραχής Hartle» και υπολογίζονται διορθώσεις στην μάζα και την ακτίνα, διορθώσεις που οφείλονται σε σφαιρικές και τετραπολικές παραμορφώσεις. Ακολούθως, εφαρμόζεται μία διαταρακτική προσέγγιση με όρους τρίτης τάξης στην γωνιακή ταχύτητα, Ω. Η στροφορμή, J, η ροπή αδράνειας, I, η περιστροφική κινητική ενέργεια, T, και η βαρυτική δυναμική ενέργεια, W, είναι ποσότητες που υφίστανται σημαντικές διορθώσεις από την προσέγγιση τρίτης τάξης. Η διαφορική περιστροφή ϑεωρείται ότι (i) υπακούει σε έναν συγκεκριμένο νόμο, ή (ii) επάγεται από το συνδυασμό ομοιόμορφης περιστροφής και ακτινικών ταλαντώσεων του αστέρα· ο στόχος είναι να υπολογισθεί η μεταβολή σημαντικών φυσικών ποσοτήτων που οφείλεται στη διαφορική περιστροφή. Στο δεύτερο μέρος, μελετάται η επίδραση του μαγνητικού πεδίου, το οποίο αποτελείται από πολοειδή και τοροειδή συνιστώσα, με τη «μέθοδο διαταραχής κατά Ioka-Sasaki» (IS). Στην παρούσα διαπραγμάτευση, το πρόβλημα περιγράφεται από μία «γενικευμένη διαφορική εξίσωση Grad-Shafranov» (GS),η επίλυση της οποίας δίνει τη συνάρτηση ροής (flux function), ψ. Μέσω αυτής της συνάρτησης υπολογίζονται οι συνιστώσες του μαγνητικού πεδίου και η γεωμετρική παραμόρφωση που υφίσταται ο αστέρας λόγω του μαγνητικού πεδίου. Η αντιμετώπιση του προβλήματος γίνεται και σε αυτήν την περίπτωση με τη ϑεωρία διαταραχών. ΄Εχοντας υπολογίσει μοντέλα περιστρεφομένων αστέρων νετρονίων και διάφορα μοντέλα με μαγνητικό πεδίο, μπορούμε να συνθέσουμε τα αποτελέσματά μας και να προσδιορίσουμε μοντέλα αστέρων νετρονίων μηδενικής φαινόμενης παραμόρφωσης (equalizers), δηλαδή αστέρων νετρονίων που η περιστροφή και το μαγνητικό πεδίο προκαλούν ίσες και αντίθετες γεωμετρικές παραμορφώσεις στο σχήμα του αστέρα. / We compute relativistic polytropic models as well as models obeying realistic equations of state, of rotating neutron stars. The purpose of this study is to calculate significant physical quantities of a neutron star, in the case of hydrostatic equilibrium, rigid and differential rotation, as well as in the case of a magnetic neutron star with both poloidal and toroidal components. A short description of the numerical treatment has as follows. First, we solve the Oppenheimer-Volkov system of differential equations. This system refers to hydrostatic equilibrium of non rotating polytropic models. Then, solid rotation is added as a perturbation, according to "Hartle’s perturbation method" and corrections to mass and radius are calculated, as also corrections due to spherical and quadrupole deformations. In addition a third order perturbation in angular velocity, Ω, is implemented. Angular momentum, J, moment of inertia, I, rotational kinetical energy, T, and gravitational potential energy, W, are quantites that are significally corrected by the third order approximation. Differential rotation is assumed that (i) obeys a specific law, or (ii) follows as a result of the solid rotation and radial oscillations combination; our purpose is the calculation of the main physical quantities that are altered by differential rotation. In the second part the effect of magnetic field is studied, which consists of a poloidal and a toroidal component. The "Ioka-Sasaki perturbation method" (IS) is implemented. This problem is described by the quantification of the flux function ψ, which comes as a solution of the "Grad-Shafranov" (GS) differential equation. Then the components of the magnetic field and the quadrupole deformation of the star are calculated. This method is also a perturbative method similar to "Hartle’s perturbation method". Having calculated models of rotating neutron stars, as also various models of magnetic fields, we can compose our results and determine models of neutron stars with zero deformation, the equalizers, these are neutron stars that are rotating and also have a magnetic field in a way that they, rotation and magnetic field, produce equal but opposite geometrical deformations in the shape of the star.

Orientador: Jun Takahashi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-11T10:21:35Z (GMT). No. of bitstreams: 1 Vasconcelos_GeraldoMagelaSeverino_M.pdf: 4363414 bytes, checksum: 50c5bd667b62ccab57088d6b77e1ec81 (MD5) Previous issue date: 2008 / Resumo: As colisões de íons pesados em energias relativísticas permitem estudar o comportamento da matéria nuclear em condições extremas de temperatura e alta densidade de energia. Nessas condições, espera-se uma transição de fase da matéria onde seria formado um estado de quarks e glúons livres, conhecido como Plasma de Quarks e Glúons (QGP). Com o objetivo de estudar a formação deste novo estado e suas características, o experimento STAR, situado no Laboratório Nacional de Brookhaven, Nova Iorque, mede vários canais observáveis das colisões de íons pesados. Uma das marcas da formação do QGP é o aumento da produção de estranheza. O objetivo deste trabalho foi estudar a produção dos bárions multi-estranhos X e W produzidos nas colisões de Cu+Cu com energia de 62,4 GeV=A no referencial do centro de massa (CM), medidos no experimento STAR. Foram obtidos os espectros de momento transverso dessas partículas e a partir deles foi extraída a abundância de produção por unidade de rapidez na região de rapidez central (dN=dy)y=0. A produção desses bárions foi comparada com os resultados de um outro sistema (Au+Au) na mesma energia para estudar a dependência da produção de estranheza em função do tamanho do sistema formado. Os resultados mostraram que a produção de estranheza cresce com o tamanho do sistema, e que este aumento é ligeiramente maior para o sistema de Cu+Cu do que Au+Au. Os resultados deste trabalho são inéditos e complementam um estudo sistemático da produção de estranheza. Também são importantes para a compreensão dos mecanismos de produção de estranheza em diferentes energias / Abstract: Relativistic heavy-ion collisions allow us to study the behavior of nuclear matter at extreme conditions of temperature and energy density. In these conditions, we expect a phase transition of matter where a free state of quarks and gluons would be formed, and that is known as Quark-Gluon Plasma (QGP). With the aim to study this new state of matter and its features, the STAR experiment was built at BNL (Brookhaven National Laboratory), New York. The STAR experiment measures many observables of heavy-ion collisions and in particular, the strangeness enhancement in QGP is of special interest. The aim of this work was the study of multi-strange baryon production, X and W , at collisions of Cu+Cu in the center of mass energy of 62.4 GeV=A measured at the STAR experiment. Transverse momentum spectra and integrated yields for X and W at mid-rapidity are presented in this work. We also compared Cu+Cu and Au+Au systems in order to study the dependence of strange particle production with the system size. The results showed that strangeness production enhances with the system size, and strange baryons yields in Cu+Cu are slightly larger than Au+Au for the same energy. The new results obtained here complement a systematic study of strangeness production in heavy ion collisions and are important to understand the strangeness particle production mechanism in different energies / Mestrado / Física Nuclear / Mestre em Física

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-07-05T20:29:06Z No. of bitstreams: 2 Dissertação - Emile Raymond Ferreira Taillebois - 2013.pdf: 1511356 bytes, checksum: 65cfae075ab1d008ea3249e5ffc19da9 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Cláudia Bueno (claudiamoura18@gmail.com) on 2017-07-07T19:11:05Z (GMT) No. of bitstreams: 2 Dissertação - Emile Raymond Ferreira Taillebois - 2013.pdf: 1511356 bytes, checksum: 65cfae075ab1d008ea3249e5ffc19da9 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-07T19:11:05Z (GMT). No. of bitstreams: 2 Dissertação - Emile Raymond Ferreira Taillebois - 2013.pdf: 1511356 bytes, checksum: 65cfae075ab1d008ea3249e5ffc19da9 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2013-11-08 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In this dissertation, the use of the partial trace of momentum degrees of freedom in the construction of spin reduced density matrices for relativistic massive systems is analyzed. In the regime considered here, massive particles can be described by irreducible unitary representations of the Poincar e group, and the base states are labeled by the dynamical variables of momentum and spin. The reduced density matrices obtained by the partial trace of momenta have unusual properties, since they are not covariant under the action of restricted Lorentz transformations. That behavior produces some important consequences in the study of quantum information in relativistic systems. However, recent arguments have been presented against the use of those matrices in the description of processes involving the transfer of information stored in spin degrees of freedom of relativistic massive particles. Those criticisms are discussed in this dissertation and a connection with the structure of the space of states associated with a given unitary representation is established through a detailed study of the induced representation method applied to the Poincar e group. This allows rewriting the criticisms in literature without the need of a speci c model of interaction for the spin measurement. Besides that, the analysis performed here allows to establish a new method to construct e ective spin reduced density matrices. The presented approach allows recovering the results in the literature and, at the same time, to incorporate the criticisms in a consistent way. However, it is necessary to abandon the usual partial trace of the momentum degrees of freedom and the interpretation in the literature for the spin reduced density matrices. The examples presented in the arguments against the usual spin reduced density matrices are studied using the approach proposed in this dissertation. / Nesta dissertação, a utilização do traço parcial dos momentos na construção de matrizes densidade reduzidas de spin para partículas massivas relativisticas é analisada. No regime considerado, as partículas massivas podem ser descritas por representações unitárias do grupo de Poincaré, e os estados de base são rotulados pelas variáveis dinâmicas de momento e spin. As matrizes reduzidas obtidas por meio do traço parcial dos momentos possuem propriedades inusitadas, pois não são covariantes sob a ação de transformações de Lorentz restritas. Essa característica traz consequências importantes para o estudo da teoria da informação quântica em sistemas relativísticos. No entanto, argumentos recentes têm sido apresentados contra o uso dessas matrizes nos processos de transmissões de informação envolvendo os graus de spin de partículas massivas. Essas críticas são discutidas neste trabalho e uma conexão com a estrutura do espaço de estados associado a representação unitária em questão é estabelecida por meio de um estudo detalhado do método das representações induzidas aplicado ao grupo de Poincaré. Isso permite reescrever as críticas presentes na literatura sem a necessidade de se introduzir um modelo específico de interação associado à medida do spin das partículas. Alem disso, a análise realizada nesta dissertação permite estabelecer um novo método para a construção de matrizes densidade reduzidas efetivas de spin. A proposta apresentada permite recuperar os resultados presentes na literatura e, ao mesmo tempo, incorporar as críticas de maneira consistente. No entanto, para isso é necessário abandonar o traço parcial usual dos graus de liberdade de momento e a interpretação dada na literatura para as matrizes densidade reduzidas de spin. Os exemplos apresentados nas argumentações contra as matrizes densidade reduzidas de spin usuais são estudados utilizando o método proposto neste trabalho.

Quand les effets de la masse finie du noyau et de la distribution de charge spatiale sont pris en compte dans l’Hamiltonien décrivant un système atomique, les isotopes d’un élément, caractérisés par le même nombre de protons mais un nombre différent de neutrons, ont des niveaux d’énergie électronique différents. Le déplacement entre les niveaux d’énergie (pour un même état quantique) de deux isotopes différents est appelé le déplacement isotopique de niveau. De manière générale, on peut distinguer les déplacements isotopiques de champ (field shift) et les déplacements isotopiques de masse (mass shift). Pour les systèmes à plus d’un électron, le specific mass shift (SMS) apparaît. Grâce à sa faible pondération, le paramètre SMS peut être traité comme une perturbation de l’Hamiltonien ;son estimation fait appel aux intégrales de Vinti [5].<p>Dans un contexte relativiste, les programmes grasp2K [2] et mcdf-gme [1] permettent de résoudre les équations de Dirac-Fock associées à un état multiconfigurationnel et d’en fournir l’énergie ainsi que la représentation numérique des orbitales monoélectroniques. Nous avons créé et introduit dans le programme mcdf-gme une sous-routine capable d’estimer les paramètres de masse et de champ à partir des fonctions d’onde multiconfigurationnelles. Pour le programme GRASP2K, un module indépendant à été créé. <p>Par ailleurs, un opérateur plus complet impliquant des corrections en αZ, a été dérivé par Shabaev [4] et, de manière indépendante, par Palmer [3]. Nous avons déduit la forme tensorielle de cet opérateur et avons également implémenté dans les programmes cités ci-dessus le calcul de ses éléments de matrice.<p>Grâce à ces outils nous avons pu étudier la détérioration de l’opérateur d’énergie cinétique pour estimer le normal mass shift et travailler divers systèmes comme le lithium neutre et sa séquence isoélectronique. Par la suite nous avons également travaillé sur les séquences isoélectroniques du bore, du béryllium, du carbone et de l’azote. Enfin, certains effets isotopiques ont été étudiés pour plusieurs transitions dans le baryum neutre.<p>Bibliographie<p>[1] J. P. Desclaux. A relativistic multiconfiguration Dirac-Fock package. In E. Clementi, editor, Methods and Techniques in Computational Chemistry - vol. A :Small Systems of METTEC, page 253. STEF, Cagliari, 1993.<p>[2] P. Jönsson, X. He, C. Froese Fischer and I. P. Grant. The GRASP2K relativistic atomic structure package. Comput. Phys. Commun. 177 :597–622, 2007.<p>[3] C. W. P. Palmer. Reformulation of the theory of the mass shift. J. Phys. B :At. Mol. Phys. 20 :5987–5996, 1987.<p>[4] V. M. Shabaev and A. N. Artemyev. Relativistic nuclear recoil corrections to the energy levels of multicharged ions. J. Phys. B :At. Mol. Phys. 27 :1307–1314, 1994.<p>[5] J. P. Vinti. Isotope shift in magnesium. Phys. Rev. 56 :1120–1132, 1939. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished