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Efeitos da quebra espontânea da simetria-CPT e da invariância de Lorentz no fenômeno da condensação de Bose-Einstein / Effects of spontaneous symmetry breaking-CPT and Lorentz invariance of the phenomenon the Bose-EinsteinSilva, Kleber Anderson Teixeira da 29 April 2011 (has links)
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Previous issue date: 2011-04-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Bose-Einstein condensate (BEC), also known as the fifth state of the matter, was predicted
theoretically by Albert Einstein in 1925 and verified experimentally 70 years later in 1995. This
dissertation addresses the effects of spontaneous broken of the CPT-symmetry and of the invariance
Lorentz (also called simply the violation of Lorentz symmetry) in the Bose-Einstein condensation
of an ideal bosonic gas in the limits nonrelativistic and will ultrarelativ´ıstico. The work is based
on a model of fields theory described by a massive complex scalar field in the framework of spontaneous
breaking of the CPT-symmetry and of the Lorentz invariance. First we study the CBE
in the nonrelativistic limit starting from the non relativistic version of our model. Thus, the existence
of the CBE imposes strong restrictions on some parameters governing the breach of Lorentz
invariance (VIL). We observed that only the critical temperature is modified by the VIL. Also,
we use experimental data to obtain limits upper for the coefficients that control the VIL. Because
of our model describe consistently the CBE in the non relativistic limit We can use it to study
the CBE ultrarelativıstica of an ideal bosonic gas loaded. Thus, we show that the construction of
a partition function well defined to describe the relativistic ideal gas, imposes strong restrictions
on two parameters that control the VIL. The analysis of the CBE in the ultrarelativistico limit
shows that both the critical temperature as the chemical potential are affected by the spontaneous
breaking of the invariance of Lorentz. / A condensação de Bose-Einstein (CBE), também conhecida como o quinto estado da matéria, foi
prevista teoricamente por Albert Einstein em 1925 e verificado experimentalmente 70 anos depois,
em 1995. Esta dissertação aborda os efeitos da quebra espontânea da simetria-CPT e da invariância
de Lorentz (também chamada simplesmente de violação da simetria de Lorentz) na condensação de
Bose-Einstein de um gás ideal bosônico nos limites não relativístico e ultrarelativístico. O trabalho
é baseado em um modelo de teoria de campos descrito por um campo escalar complexo massivo
no marco da quebra espontânea da simetria-CPT e da invariância de Lorentz. Primeiro estudamos
a CBE no limite não relativístico partindo da versão não relativística do nosso modelo. Desse
modo, a existência da CBE impõe restrições severas sobre alguns parâmetros que regem a violação
da invariância de Lorentz (VIL). Observamos que somente a temperatura crítica é modificada
pela VIL. Também, usamos dados experimentais para obter limites superiores para os coeficientes
que controlam a VIL. Pelo fato do nosso modelo descrever de modo consistente a CBE no limite
não relativíıstico podemos usá-lo para estudar a CBE ultrarelativística de um gás ideal bosônico
carregado. Assim, mostramos que a construção de uma função de partição bem definida, para
descrever o gás ideal relativístico, impõe restrições severas sobre dois parâmetros que controlam a
VIL. A análise da CBE no limite ultrarelativístico mostra que tanto a temperatura crítica como o
potencial químico são afetados pela quebra espontânea da invariância de Lorentz.
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Matrizes de massa e violação CP / Mass matrices and CP violationGaydutschenko, Larissa, 1987- 19 May 2006 (has links)
Orientador: Orlando Luis Goulart Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-23T16:45:26Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013 / Resumo: O fenômeno de oscilação de neutrinos, já experimentalmente observado, só pode ser explicado se a massa dos neutrinos for diferente de zero. No entanto, até pouco tempo atrás, acreditava-se que neutrinos não tivessem massa. O Modelo Padrão das partículas elementares ainda não é capaz de descrever a natureza massiva dos neutrinos, de forma que as matrizes de mistura para léptons (entre autoestados de gauge e autoestados de massa), análogas às matrizes de mistura de quarks, ainda não podem ser encontradas. Através de uma pequena extensão do Modelo Padrão, é possível descrever uma física que leva em conta essas massas e que, portanto, nos fornece essas matrizes de mistura. Essa extensão trata-se de nada mais que o acréscimo de uma nova partícula ao modelo, um lépton neutro que não interage por força fraca. Essa partícula é chamada de neutrino estéril. Portanto, acrescentando um ou mais neutrinos estéreis ao Modelo Padrão posso obter a matriz de mistura para léptons e, consequentemente, contar o número de parâmetros físicos que ela possui. O interesse em contar esses parâmetros reside no fato de que encontrar o número de fases complexas presentes na matriz de mistura é equivalente a encontrar o número de fases de violação de simetria conjugação de carga e paridade (CP) para léptons. Em 1967, o físico russo Andrei Sakharov propôs uma forma de explicar a assimetria bariônica (matéria-antimatéria) partindo de um estado simétrico. Para isso, algumas condições precisariam ser respeitadas pela física do universo. Uma dessas condições é que exista na natureza uma fonte de violação CP. Procurar essa violação em léptons foi o objetivo deste trabalho. Assim, foi possível obter a matriz de mistura para léptons estendendo o modelo padrão pela adição de um neutrino estéril e levando em conta o caso geral de n famílias de léptons. Uma vez tendo encontrado a matriz de mistura, fizemos a contagem dos parâmetros. Além abranger os cálculos usados para encontrar o número de fases complexas damatriz, a dissertação apresenta uma breve introdução à teoria quântica de campos, a simetrias discretas e ao mecanismo de quebra espontânea de simetria, conceitos necessários para o entendimento do trabalho realizado / Abstract: The neutrino oscillation phenomenum, already experimentally observed, can only be explained if neutrino masses are different from zero. However, till recently, it was believed that neutrinos were massless. The Standard Model of elementary particles is yet not able to describe the massive nature of neutrinos, such that the lepton mixing matrix (between gauge eigenstates and mass eigenstates), analogous to the quark mixing matrix, can still not be found. Through a small extension of the Standard Model, it is possible to describe physics that take into account these masses and, therefore, provides us with these mixing matrices. This extension is nothing but the addition of a new particle, a neutral lepton that does not interact through weak force. This particle is called sterile neutrino. So, by adding one or more sterile neutrinos to the Standard Model, I can get the lepton mixing matrix and consequently count the number of physical parameters that it presents. The interest in counting these parameters resides in the fact that finding the number of complex phases in the mixing matrix is equivalent to finding the number of charge conjugation-parity (CP) violation for leptons. In 1967, the Russian physicist Andrei Sakharov proposed a way to explain the baryonic asymmetry (matter-antimatter) beginning with a symmetric state. For that to work some conditions needed to be respected by the universe physics. One of them is that there must exist in nature a source of CP violation. Looking for that source as the leptonic sector of the particle physics was the goal of this project. And finally it was possible to get the lepton mixing matrix extending the standard model by the addition of one sterile neutrino and taking into account the general case of n lepton families. Once we got the mixing matrix, we counted the physical parameters. Besides presenting all the calculation used for finding the number of complex phases in the matrix, this thesis presents a brief introduction to quantum field theory, discrete symmetries and the spontaneous symmetry breaking mechanism, all of these concepts being necessary for the understanding of the work accomplished / Mestrado / Física / Mestra em Física
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Ultrafast investigation of electronic and structural dynamics in photomagnetic molecular solids / Ultrarapidité de la dynamique électronique et structurale dans des solides moléculaires photomagnétiquesMarino, Andrea 16 July 2015 (has links)
La capacité de photo-commuter les propriétés physico-chimiques des matériaux fonctionnels grâce à des transitions de phase induites par la lumière, ouvre des perspectives fascinantes pour diriger un matériau vers un nouvel état hors équilibre thermique. Cependant, il est fondamental de comprendre tous les phénomènes élémentaires, habituellement cachés dans une moyenne statistique lors des transformations à l'équilibre. Les études résolues en temps représentent une approche unique pour accéder à l'évolution des différents degrés de liberté du système et connaître les processus élémentaires mis en jeu lors de la commutation macroscopique. Les matériaux à transition de spin (SCO) sont d'un intérêt particulier car ce sont des systèmes photo-réversibles. Ces matériaux sont aussi des prototypes photomagnétiques et photochromiques qui commutent entre deux états de différente multiplicité de spin, nommés bas spin (LS) et haut spin (HS). Dans ce travail de thèse, nous étudions les dynamique ultrarapides électroniques et structurales de cette classe de solides moléculaires, en soulignant l'importance d'utiliser des sondes complémentaires sensibles à différents degrés de liberté. Les commutation photo-induite entre états de spin est ultra-rapide et initialement localisée à l'échelle moléculaire, où le couplage électron-phonon active des vibrations cohérentes intramoléculaires. Un transfert d'énergie ultra-rapide de la molécule au réseau, via un couplage phonon-phonon, permet de piéger efficacement le système dans le nouvel état photo-induit. Cependant, dans les solides moléculaires, l'excès d'énergie libérée de la molécule excitée résulte dans un aspect complexe multi-échelle impliquant plusieurs degrés de liberté à des échelles de temps différentes. Dans ce travail de thèse, nous avons étudié la dynamique multi-étape hors équilibre d'un système SCO présentant une brisure de symétrie entre la phase HS et la phase intermédiaire (IP) où une mise en ordre à longue distance des états HS et LS des molécules résulte en la formation d'une onde de concentration de spin (SSCW). La diffraction des rayons X résolue en temps combinée avec des études de spectroscopie optique donnent une description complète de la dynamique hors-équilibre de la SSCW hors-équilibre en mesurant l'évolution temporelle des deux paramètres d'ordre décrivant le système. / The ability to photo-switch physical/chemical properties of functional materials through photo induced phase transition opens fascinating perspectives for driving the material towards new state out of thermal equilibrium. However, it is fundamental to disentangle and understand all the dynamical phenomena, otherwise hidden in statistically averaged macroscopic transformations. Arguably, time-resolved studies are unique approach to access the necessary information on the multiple degrees of freedom and elementary processes involved during the macroscopic switching. As photo-reversible molecular switches, spin crossover (SCO) materials are of particular interest. These photomagnetic and photochromic prototype materials undergo metastable photoinduced phase transition between two states of different spin multiplicity, namely low-spin (LS) and high-spin (HS). In this PhD work it will be presented the ultrafast electronic and structural dynamics of SCO molecular solids emphasizing the importance of using complementary probes sensitive to different degrees of freedom. The photoinduced spin state switching concerns initially only an ultrafast, but localized, molecular response which through strong electron-phonon coupling activates coherent intra-molecular vibrations. An ultrafast energy transfer from the molecule to the lattice, via phonon-phonon coupling, allows an efficient trapping of the system in the new photoinduced state. However in molecular solids, the excess of energy released from the absorber molecule results in a complex multi-scale aspect involving several degrees of freedom at different time scales. In this contest, we investigated the multi-step out-of equilibrium dynamics of a SCO system undergoing symmetry breaking between the HS phase and the intermediate (IP) phase where a long range ordering of HS and LS molecules results in a spin state concentration wave (SSCW), analogous to charge or spin density waves. Combined time-resolved X-ray diffraction and optical spectroscopy studies provide a complete overview of the out-of-equilibrium thermodynamics of the SSCW, investigating how the two order parameters describing the system evolve in time.
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The developmental polarity and morphogenesis of a single cell / Développement de la morphogenèse et de la polarité d’une cellule uniqueBonazzi, Daria 06 March 2015 (has links)
Comment les cellules établissent leurs formes et organisations internes est un problème biologique fondamental. Au cours de cette thèse, j’ai étudié le développement de la forme cellulaire et de la polarité chez la cellule de levure fissipare. Ces études sont fondées sur l’exploration de la façon dont les petites spores symétriques de levures se développent et s’organisent pour briser la symétrie pour la définition de leur tout premier axe de polarité. Dans une première partie, j’ai étudié les couplages entre la mécanique de surface de la paroi cellulaire des spores et la stabilité de domaines de polarité de Cdc42 qui contrôlent les aspects spatio-temporelles de la brisure de symétrie de ces spores. Dans une seconde partie, j’ai étudié les mécanismes par lesquels ces domaines de polarité contrôlent leur taille et l'adapte à la géométrie de la cellule, un processus vraisemblablement pertinents pour comprendre comment des domaines fonctionnels corticaux s’adaptent à la taille des cellules. Globalement, ces nouvelles recherches focalisant sur la façon dont les cellules développent dynamiquement leur forme et polarité de novo, permettent de mettre en évidence des couplages complexes dans la morphogenèse qui ne peuvent pas être testés en regardant les cellules à « l’état stationnaire» ou avec des outils génétiques. / How cells establish their proper shapes and organization is a fundamental biological problem. In this thesis, I investigated the dynamic development of cellular form and polarity in the rod-shape fission yeast cell. These studies are based on monitoring how small symmetric fission yeast spores grow and self-organize to break symmetry for the definition of their very first polarity axis. In a first part, I studied interplays between surface mechanics of the spore cell wall and the stability of Cdc42-based polarity domains which control spatio-temporal aspects of spore symmetry breaking. In a second part, I studied mechanisms by which these polarity domains control their width and adapt it to cell surface geometry, a process likely relevant to understand how functional cortical domains scale to cell size. Overall these novel investigations focusing on how cells dynamically develop their form and polarity de novo highlight complex feedbacks in morphogenesis that cannot be evidenced by looking at cells at “steady state” or with genetics.
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Perturbative perspectives on the Phase diagram of Quantum ChromoDynamics / Points de vue perturbatifs sur le diagramme de phases de la chromodynamique quantiqueMaelger, Jan 10 October 2019 (has links)
L'étude du diagramme des phases de la Chromodynamique Quantique (QCD) et des transitons associées (déconfinement et restoration de la symétrie chirale) représentent des défis majeurs de la Physique moderne et nombreuses sont les approches théoriques qui visent à en sonder les multiples facettes. Du fait de l'intensité de l'interaction forte dans les régimes d’énergie pertinents pour les transitions susmentionnées, ces approches sont en général de nature non-perturbative, la théorie des perturbations étant réputée inapplicable à ces échelles. Il est, cependant, bien établi que le point de départ de la théorie usuelle des perturbations, basée sur la procédure de fixation de jauge de Faddeev-Popov, est ambigu à ces échelles (ambiguïté de Gribov). Dans ce contexte, une approche perturbative modifiée, basée sur le Lagrangien de Curci et Ferrari, a été proposée, via l’ajout phénoménologique d'un terme de masse effectif pour le gluon en jauge de Landau. Cette approche a été testée avec succès, notamment dans sa capacité à reproduire les fonctions de corrélation de la théorie Yang-Mills (et QCD dans la limite de quarks lourds) et la thermodynamique à temperature et potentiel chimique non nuls.Dans cette thèse, nous avons testé la robustesse de ces résultats en évaluant la structure de phase de la QCD avec quarks lourds au deuxième ordre de la théorie des perturbations dans le modèle de Curci-Ferrari et en comparant nos résultats à ceux d'approches nonperturbatives. Nos résultats indiquent que, dans ce régime de quarks lourds, le diagramme de phases est contrôlée perturbativement. Nous avons égalementétendu notre étude au cas de la QCD avec quarks légers en utilisant un schéma de resommation qui exploite la présence de petits paramètres dans le régime infrarouge de la QCD. Dans le secteur des quarks, cette démarche donne lieu à la resommation des fameux diagrammes dits "arc-en-ciel”. Ici, nous généralisons ce formalisme à temperature et densité non nulles et en presence d'un champ de fond gluonique. Nous réalisons une toute première étude qualitative des prédictions du modèle CF concernant l’existence possible d’un point critique dans le diagramme de phases de QCD sur la base d’une version simplifiée des équations générales ainsi obtenues. / Unravelling the structure of the QCD phase diagram and its many aspects such as (de)confinementand chiral symmetry breaking, is one of the big challenges of modern theoretical physics, and manyapproaches have been devised to this aim. Since perturbation theory is believed to cease feasibilityat low energy scales, these approaches treat the relevant order parameters, the quark condensate andthe Polyakov loop, non-perturbatively. However, it is also well-established that the starting point forperturbation theory, the Fadeev-Popov gauge-fixing procedure, is inherently ill-defined in the infrareddue to the presence of Gribov ambiguities. In this context, a modified perturbative approach based onthe Curci-Ferrari Lagrangian has been introduced, where a phenomenologically motivated effective gluonmass term is added to the Landau gauge-fixed action. Prior to the beginning of the thesis, this approach hasproven extremely fruitful in its descriptions of (unquenched) Yang-Mills correlation functions and thermodynamics at (non)zero temperature and density.Throughout the thesis we extend this analysis to the entire phase structure of QCD and QCD-liketheories and test the validity of the model in various regimes of interest. For instance, to further aprevious one-loop study in the regime of heavy quark masses, we have computed the two-loop quarksunset diagram in the presence of a non-trivial gluon background in a finite temperature and densitysetting. We come to the conclusion that the physics underlying center symmetry is well-described by our perturbative model with a seemingly robust weak-coupling expansion scheme. Furthermore, we study the regime of light quarks by means of a recently proposed resummation scheme which exploits the presence of actual small parameters in the Curci-Ferrari description of infrared QCD. In the quark sector, this leads to the renown rainbow equations. We extend this first-principle setup to nonzero temperature, chemical potential, and gluon background. We perform a first qualitative analysis of the prediction of the model concerning the possible existence of a critical endpoint in the QCD phase diagram by using a simplified version of these general equations.
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Manipulation of time reversal symmetry breaking superconductivity in Sr₂RuO₄ by uniaxial pressureGhosh, Shreenanda 30 September 2021 (has links)
Unconventional superconductivity continues to be one of the most striking chapters in condensed matter physics, by posing challenges to our theoretical understanding
of its origin. During the last three decades a large number of unconventional superconductors with exotic properties have been found arising great interest, such
as the heavy fermion systems, high Tc cuprates as well as the Iron based superconductors etc. Sr2RuO4, the material I have studied, can be considered as an
exemplary case in this regard. In spite of more than two decades of comprehensive research, Sr2RuO4 remains one of the most compelling superconductors till date.
Various experimental results give evidence that the superconductivity of Sr2RuO4 is chiral: including measurements of the Kerr effect, sound velocities, critical currents
across junctions, and muon spin relaxation(μSR), the experimental technique at the heart of this dissertation. Recent NMR Knight shift measurements suggests that
the pairing is most likely spin-singlet, and in the tetragonal lattice of Sr2RuO4, the combination of singlet pairing and chirality compels consideration of an seemingly
unlikely order parameter: dxz ± idyz. It is unlikely because it comes along with a horizontal line node at kz = 0, whereas Sr2RuO4 has a very low c-axis conductivity.
And that makes the question whether or not the superconductivity of Sr2RuO4 is chiral, of great importance. This calls for an unique scenario in regard to our
understanding of unconventional superconductivity, as the presence of chirality in Sr2RuO4 might imply a new form of pairing, which is yet to be firmly determined.
Chiral superconductors break time reversal symmetry by definition, and in general time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two component order parameters. Probing Sr2RuO4 under uniaxial pressure offers the possibility to lift the degeneracy between such components. However, despite strenuous efforts, a splitting of the superconducting and TRSB transitions under uniaxial pressure has not been observed so far. In this thesis, I report muon spin relaxation measurements on Sr2RuO4 samples, placed under uniaxial stress. The relatively large sample size suitable for μSR demanded for a customized uniaxial pressure cell in order to perform our experiments. It has been a technically challenging task to have a fully fledged uniaxial pressure cell with stringent requirements, that is suitable for time restricted facility experiments like μSR. The technical advancement has been documented thoroughly in this thesis. Using the dedicated uniaxial pressure cell, we observed the much awaited stress induced splitting between the onset temperatures of superconductivity and time reversal symmetry breaking, consistent with the qualitative expectations for a chiral order parameter in Sr2RuO4. In addition to that, we report the appearance of a bulk magnetic order in Sr2RuO4 under higher uniaxial stress for the first time, above the critical pressure at which a Lifshitz transition is known to occur. The signal in the state appearing at high stress qualitatively differs from that in the TRSB
state in unstressed Sr2RuO4, which provides evidence that the enhanced muon spin relaxation at lower stresses is not a consequence of conventional magnetism. As
a whole, our results strongly support the idea of two-component superconducting order parameter in Sr2RuO4, that breaks time-reversal symmetry.
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Search for resonant WZ production in the fully leptonic final state with the ATLAS detectorFreund, Benjamin 07 1900 (has links)
Diboson resonance searches are an essential test of electroweak symmetry breaking
theories beyond the Standard Model (SM) of particle physics. Vector or scalar resonances
decaying to dibosons are predicted by various models going beyond theSM, such as Grand
Unified theories, Little Higgs models, Composite Higgs models or models with extended
Higgs sector (such as Super Symmetry (SUSY) or two-Higgs-doublet models). This
thesis presents a search for resonant WZ production in the fully leptonic decay channel
ℓν ℓℓ (ℓ = e or μ) with two production modes : quark-antiquark fusion or vector-boson
fusion. Using 36.1 fb−1 of recent data collected by the ATLAS detector in pp collisions
delivered by the Large Hadron Collider (LHC) at 13 TeV, constraints are obtained on
models going beyond the SM.
Since this analysis considers the fully leptonic decays of the vector bosons, events
with exactly three leptons in the final state and a substantial missing transverse energy
are selected. One signal region is established for each production mode of the resonance,
either by quark-antiquark or vector boson fusion. For heavy vectorial resonances produced
by quark fusion the W and Z bosons are required to carry a substantial fraction of the
resonance energy (pWT
/mWZ > 0.35 and pZT /mWZ > 0.35)). Events with resonances
produced by vector boson fusion are characterised by two jets with a large invariant mass
and a large separation in pseudorapidity. Therefore, in the search for this production mode,
events are required to have at least two jets with an invariant mass (mj j ) greater than
500 GeV and a separation in pseudorapidity ( ηj j ) of at least | ηj j | > 3.5. In each signal
region the distribution of the invariant mass of the WZ system will then be examined
to determine the presence or absence of new resonances that manifest themselves as
localised excesses in the invariant mass of the diboson system (mWZ).
No significant excess was observed in the signal regions. Limits have then been set on
the cross section times branching ratio for a heavy vector resonance produced by either
quark-antiquark or vector boson fusion. Additionally, limits on the coupling parameters
and masses are obtained for a charged Higgs boson in the Georgi-Machacek produced
by vector boson fusion. / Les recherches de résonances di-boson constituent un test essentiel des théories de
brisure de symétrie électrofaible au-delà du modèle standard (MS). Plusieurs scénarios,
comme les théories de grande unification, les modèles Little Higgs, les modèles de Higgs
Composés ou celles avec un secteur de Higgs élargi (par example SUSY ou le two-Higgsdoublet
model), prédisent des résonances vectorielles ou scalaires. Cette thèse présente
une recherche de résonances lourdes se désintégrant en WZ dans le canal leptonique
WZ → ℓν ℓℓ (ℓ = e ou μ). Deux modes de production sont considérés : par fusion de
quark-antiquark ou par fusion de boson vectoriels. Se basant sur les récentes données
recueillies par le détecteur ATLAS lors de collisions pp à 13 TeV au LHC au cours
des années 2015 et 2016, avec une luminosité intégrée de 36.1 fb−1, on établira des
contraintes sur des modèles allant au-delà du MS de la physique des particules.
Puisqu’on considère la désintégration leptonique des bosons WZ, on sélectionne les
événements ayant trois leptons et une grande énergie transverse manquante. Des régions
de signal sont choisies pour chaque mode de production : fusion par quarks ou par
bosons vectoriels. Pour les résonances produites par fusion de quark, on considère des
résonances vectorielles lourdes. On sélectionne donc des événements où les bosonW et Z
portent une fraction importante de l’énergie de masse de la résonance (pWT
/mWZ > 0.35
et pZT
/mWZ > 0.35). Les résonances produites par fusion de bosons sont caractérisées par
deux jets ayant une grande séparation en pseudorapidité et une grande masse invariante.
Pour la région de signal, dans ce cas, on requiert alors au moins deux jets avec une
masse invariante supérieure à mj j > 500 GeV et une grande séparation en pseudorapidité
| ηj j | > 3.5. Pour les deux régions, la distribution en masse invariante du système
WZ sera examinée pour déterminer la présence ou non de nouvelles résonances qui se
manifesteraient par un excès localisé.
En fin de compte, aucun excès significatif n’a été observé dans les régions de signal,
ce qui permet d’établir des limites sur le produit de la section efficace et du rapport
d’embranchement d’un boson massif vectoriel dans les deux canaux de production. Des
contraintes sont également obtenues sur la masse et le couplage d’un boson de Higgs chargé du modèle Georgi-Machacek, produites par fusion de bosons vectoriels.
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QFT and Spontaneous Symmetry BreakingChauwinoir, Sheila January 2020 (has links)
The aim of this project is to understand the structure of the Standard Model of the particle physics. Therefore quantum field theories (QFT) are studied in the both cases of abelian and non-abelian gauge theories i.e. quantum electrodynamics (QED), quantum chromodynamics (QCD) and electroweak interaction are reviewed. The solution to the mass problem arising in these theories i.e. spontaneous symmetry breaking is also studied. / Syftet med detta projekt är att förstå strukturen för partikelfysikens standardmodell. Därför studeras kvantfältsteorier (QFT) i båda fallen av abelska och icke-abelska gaugeteorier, dvs kvantelektrodynamik (QED), kvantkromodynamik (QCD) och elektrosvag växelverkan granskas. Lösningen på massproblemet som uppstår i dessa teorier, dvs. spontant symmetribrott studeras också.
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Bogoliubov Many-Body Perturbation Theory for Nuclei : Systematic Generation and Evaluation of Diagrams and First ab initio Calculations / Théorie de perturbation à N corps de Bogolioubov pour les noyaux : Génération et évaluation automatique des diagrammes et premiers calculs ab initioArthuis, Pierre 27 September 2018 (has links)
Les dernières décennies ont donné lieu à un développement rapide des théories ab initio visant à décrire les propriétés des noyaux à partir de l'interaction nucléonique. Un tel développement a été rendu possible à la fois par la très importante croissance de la puissance de calcul et de nouveaux développements formels. Le présent travail se consacre au développement de la théorie de perturbation à N corps de Bogolioubov récemment proposée, qui repose sur l'usage d'un état de référence brisant la symétrie associée au nombre de particules pour permettre une description des noyaux à simple couche ouverte. Le formalisme est tout d'abord décrit en détails, son lien avec la théorie de perturbation à N corps standard est établi, tout comme sa connexion avec la théorie de cluster couplés de Bogolioubov. L'extension du formalisme à des ordres plus élevés à partir de méthodes de théorie des graphes est ensuite présentée ainsi que le programme ADG qui génère et évalue les diagrammes BMBPT à un ordre quelconque. Les implications de ce développement formel dépassent le cadre du présent travail, les méthodes développées pouvant être appliqués à d’autres méthodes à N corps. Pour terminer, de premiers résultats numériques pour les isotopes de l'oxygène, du calcium et du nickel sont présentés. Ces résultats établissent la théorie de perturbation à N corps de Bogolioubov comme une méthode de premier intérêt pour des calculs à grande échelle sur les chaînes isotopiques et isotoniques de masse moyenne. / The last few decades in nuclear structure theory have seen a rapid expansion of ab initio theories, aiming at describing the properties of nuclei starting from the inter-nucleonic interaction. Such an expansion relied both on the tremendous growth of computing power and novel formal developments. This work focuses on the development of the recently proposed Bogoliubov Many-Body Perturbation Theory that relies on a particle-number-breaking reference state to tackle singly open-shell nuclei. The formalism is first described in details, and diagrammatic and algebraic contributions are derived up to second order. Its link to standard Many-Body Perturbation Theory is made explicit, as well as its connexion to Bogoliubov Coupled-Cluster theory. An automated extension to higher orders based on graph theory methods is then detailed, and the ADG numerical program generating and evaluating BMBPT diagrams at arbitrary order is introduced. Such a formal development carries implications that are not restricted to the present work, as the developed methods can be applied to other many-body methods. Finally, first numerical results obtained for oxygen, calcium and nickel isotopes are presented. They establish BMBPT as a method of interest for large-scale computations of isotopic or isotonic chains in the mid-mass sector of the nuclear chart.
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Measurement of the Partial Widths Ratio Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) at the BABAR ExperimentDickopp, Martin 22 July 2004 (has links)
Unter Benutzng von 90.4/fb Daten, die das BABAR-Experiment in den Jahren 1999 bis 2002 genommen hat, wurden die Zerfälle Ds*+ -> Ds+ pi0 und Ds*+ -> Ds+ gamma mit zwei verschiedenen Methoden rekonstruiert. Die Rekonstruktions-Effizienzen wurden mittels Signal-Monte Carlo-Ereignissen und D*0-Zerfällen ermittelt. Auf diese Weise wurde das Partialbreiten-Verhältnis Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) auf vier verschiedene Weisen gemessen. Zusätzlich wurde das Partialbreiten-Verhältnis Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) gemessen. / Using 90.4/fb of data taken at the BABAR experiment in the years 1999 to 2002, the decays Ds*+ -> Ds+ pi0 and Ds*+ -> Ds+ gamma have been reconstructed with two different methods. Signal Monte Carlo events as well as D*0 decays have been used to determine the reconstruction efficiencies. Thereby, the partial widths ratio Gamma(Ds*+ -> Ds+ pi0) / Gamma(Ds*+ -> Ds+ gamma) has been measured in four different ways. Additionally, the partial widths ratio Gamma(D*0 -> D0 pi0) / Gamma(D*0 -> D0 gamma) has been measured.
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