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Investigamos o papel da interação forte nas colisões periféricas de íons pesados, contrastando-a com a interação eletromagnética, e o efeito que ela desempenha na excitação de modos coletivos, processos envolvendo a correlação de dois núcleons e processos completamente incoerentes. Explicamos dados experimentais recentes (Brookhaven, E814 Collaboration), separando quantitativa e qualitativamente as contribuições nuclear e eletromagnética, coerentes e incoerentes, comparando-as também com outras experiências similares. / We have compared the role played by strong interactions with the one played e1ectromagnetic interactions in re1ativistic heavy ion collisions. We also analyze its effects of strong interactions in the excitation of collective modes and in the emission of one and two-nucleon correlations. We explain recent experimental data (Brookhaven, E814 Collaboration), separating qualitatively and quantitatively the nuclear and electromagnetic, coherent and incoherent contributions to the one-nucleon emission cross section. We also compare them with results of other similar experiments.

Investigamos o papel da interação forte nas colisões periféricas de íons pesados, contrastando-a com a interação eletromagnética, e o efeito que ela desempenha na excitação de modos coletivos, processos envolvendo a correlação de dois núcleons e processos completamente incoerentes. Explicamos dados experimentais recentes (Brookhaven, E814 Collaboration), separando quantitativa e qualitativamente as contribuições nuclear e eletromagnética, coerentes e incoerentes, comparando-as também com outras experiências similares. / We have compared the role played by strong interactions with the one played e1ectromagnetic interactions in re1ativistic heavy ion collisions. We also analyze its effects of strong interactions in the excitation of collective modes and in the emission of one and two-nucleon correlations. We explain recent experimental data (Brookhaven, E814 Collaboration), separating qualitatively and quantitatively the nuclear and electromagnetic, coherent and incoherent contributions to the one-nucleon emission cross section. We also compare them with results of other similar experiments.

The energy-momentum tensor (EMT) is the Noether current associated with translations. It is of interest because, first of all, it has physical meaning as it contains the energy density and the momentum density. Moreover, its trace can be related to the beta function so that the scaling behaviour of the theory at hand can be studied. We are particularly interested in the scaling behaviour of strongly coupled theories. To explore the strong coupling regime it is necessary to compute the EMT non-perturbatively, i.e. on the lattice. This complicates matters greatly. On the lattice translation invariance is broken which leads to additional terms in the translation Ward identity from which the EMT is derived. This results in turn in the need to renormalise the EMT on the lattice. In this thesis we extend recent studies on the renormalisation of the EMT in four-dimensional gauge theory to the case of a three-dimensional scalar theory to investigate its divergence structure and the numerical feasibility of the suggested procedure on a more basic level. Furthermore, scalar φ4-theory in three dimensions exhibits an infrared fixed point and can thus serve as a toy model to examine mechanisms for building theories beyond the standard model. Our strategy to renormalise the EMT on the lattice is to identify all possible terms that can mix with both sides of the translation Ward identity. The renormalised EMT is a combination of operators of the same or lower dimension obeying the symmetries of the theory. The mixing is determined by requiring that the renormalised EMT satisfies the correct Ward identities. Using different probes in the translation Ward identity one can compute the coefficients of the EMT by solving a linear system of equations. However, contact terms can arise. One solution is the recently introduced Wilson flow. Its renormalisation properties allow for expectation values free of contact terms. That way the Wilson flow provides for a meaningful theoretical formulation of the EMT on the lattice that can be used in practice. In this thesis we review the renormalisation properties and the phase diagram of scalar φ4-theory in three dimensions, the translation Ward identity and the EMT in the continuum, as well as the gradient flow for scalar theory. A large part is dedicated to the perturbative renormalisation of the EMT on the lattice. Finally, our strategy to compute the renormalisation constants of the EMT in scalar theory non-perturbatively is discussed in detail, and our results for the renormalisation constants are presented.

Au LHC, la collision de particules de très hautes énergies permet d’étudier l’interaction forte. En particulier, lors de la collision de deux noyaux (de plomb pour le LHC), un nouvel état de la matière, appelé Plasma de Quarks Gluons (QGP), est créé. L’étude de ce QGP constitue actuellement un des domaines actif de la recherche en physique. Les sondes dures, telles les quarks lourds ou les photons prompts, sont produit dés les premiers instants des collisions faites au LHC. Cette caractéristique les rend idéales pour l’étude du QGP. Elles vont traverser et interagir avec le milieu créé. En comparant avec un cas sans QGP (collisions proton-proton), il sera possible d’évaluer l’influence du plasma sur ces sondes dures et d’en extraire les propriétés telles la température et la densité. Cette étude nécessite donc d’avoir une bonne connaissance de la production de ces sondes dures dans les collisions proton-proton. Le but de ma thèse est l’implémentation des quarks lourds et des photons prompts dans le générateur d’évènements EPOS (codes informatique simulant les collisions), pour les collisions p-p. Le but final sera d’utiliser ce travail pour l’étude du plasma dans les collisions Pb-Pb / At the LHC, strong interaction is studied by doing collisions of high energy particles. In the case of nucleus-nucleus collision (lead at the LHC), a new state of matter, called Quarks Gluons Plasma (QGP), is created. The study of this QGP is currently a lively research field. Hard probes, like heavy quarks and prompt photons, are produced during early times of collisions done at the LHC. This is why they are ideal probes for the study of the QGP. They will go through and interact with the medium produced by the collision. A comparison with a case without QGP (proton-proton- collision) will allow us to see how hard probes properties are modified by themedium. Then, medium properties like temperature and density can be extracted. This study requires a good understanding of hard probes production in proton-proton collisions. The aim of my thesis is the implementation of heavy quarks and prompt photons in the event generator EPOS (computer code for colliders), for p-p collisions. Our final aim is the study of the QGP in Pb-Pb collisions.

The aims of this thesis project have been to determine the feasibility of hyperon reconstruction utilizing a newly developed and implemented vertex fitter based on the Lagrange multiplier method. This was achieved through simulation and subsequent analysis of the reaction specified below, detailing the production of Λ-hyperon and K+ -meson pairs from proton-proton collisions. 𝑝(4.5𝐺𝑒𝑉)𝑝 → ΛΛ𝐾+𝐾+ This reaction channel provides a more complicated topology than previous benchmark studies of the fitter performance and is of interest as it enables studies of the strong ΛΛ interaction via the femtoscopy method. For this reason, measurements of this reaction channel were among the physics goals of the HADES beam time taking place in February 2022. As such, this study has provided insight into the feasibility of performing a femtoscopy analysis on this data by reconstructing the Λ-pair using the fitter. The obtained results provide the Λ-pair reconstruction efficiency and purities based on the lower limit of expected events collected during this beamtime. As for the fitter performance, it was found from the reconstructed kinematics of the Λ-pair that the fitter can effectively remove background over most of the kinematic region. However, for low relative momentum, combinatorial background becomes especially prominent. As this region is of interest in a femtoscopy study, it has been identified as especially challenging for the developed analysis procedure.

L'objectif de la thèse a été d'étudier les propriétés dynamiques des polymères à grande densité d'interactions fortes intermoléculaires, en fonction de l'énergie et de la densité de ces interactions. Cette étude s'est effectuée par la méthode de la dynamique moléculaire. Deux types d'interactions fortes ont étés proposés et implémentés numériquement. Un premier modèle dit isotrope dans lequel des interactions fortes sont modélisées par un potentiel isotrope, représentant par exemple des interactions ioniques. Et un second modèle dans lequel nous avons choisi un potentiel directionnel, modélisant les liaisons polaires ou les liaisons hydrogènes. L'unité de l'énergie des interactions fortes intermoléculaires a été fixée par rapport aux forces de Van der Waals des monomères non polaires qui forment la partie principale des polymères considérés J'ai étudié la dynamique de la relaxation à grande échelle (mode de Rouse) en fonction des paramètres pertinents (l'énergie et la densité) dans le régime dit Williams-Landel-Ferry (WLF). Ensuite, nous avons étudié les mécanismes de relaxation à petite échelle (monomérique) en cherchant à mettre en évidence des mécanismes spécifiques à ces polymères à fortes interactions. Nous avons également étudié la relaxation du stress. Nous avons mis en évidence une relaxation à temps intermédiaire entre le temps monomérique te les temps longs pendant laquelle le stress reste à un niveau relativement élevé, sur des échelles de temps comparables à ceux des mécanismes de relaxation spécifiques mis en évidence au niveau microscopique. Ce régime spécifique de relaxation du stress qui n'est pas observé à faible fraction de liaisons fortes est susceptible de dominer les propriétés mécaniques et viscoélastiques de ces polymères à l'état fondu. Nous avons également considéré le comportement ultime de ces polymères en étudiant les mécanismes de la cavitation. L'énergie à la rupture peut être augmentée par la présence de liaisons fortes à suffisamment forte densité le long des chaînes. Les systèmes à forte densité de liaisons polaires ne font plus apparaître de cavitation mais exhibent un comportement de strain hardening / The aim of the thesis is to study the dynamic properties of polymers with high densities of strong intermolecular interactions, depending on the energy and the density of these interactions. This study is carried out by the molecular dynamics method

Submitted by Verena Pereira (verenagoncalves@uefs.br) on 2018-07-11T23:13:30Z No. of bitstreams: 1 DIsserta??o Alexsandro VFA HIST?RIA DO M?SON PI .pdf: 9797951 bytes, checksum: 05cccd1dc1df86aff95c514b9ac8f4ab (MD5) / Made available in DSpace on 2018-07-11T23:13:30Z (GMT). No. of bitstreams: 1 DIsserta??o Alexsandro VFA HIST?RIA DO M?SON PI .pdf: 9797951 bytes, checksum: 05cccd1dc1df86aff95c514b9ac8f4ab (MD5) Previous issue date: 2017-08-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This work represents our contribution to disseminate Brazilian Physics in the classroom. It consists of a qualitative research about the insertion of topics of Particle Physics through a conceptual approach, particularly the first proposal of Yukawa for strong interaction, from the history of the discovery of the ? meson with the contributions of the brazilian scientist, C?sar Lattes. The research consisted in the elaboration, application and evaluation of a didactic sequence based on the theory of significant learning of David Ausubel / Com este estudo, pretende-se contribuir para a divulga??o da F?sica brasileira em sala de aula. Ele consiste em uma pesquisa qualitativa que trata da inser??o de t?picos de F?sica de Part?culas atrav?s de abordagem conceitual, particularmente a primeira proposta de Yukawa para intera??o forte, a partir da hist?ria da descoberta do m?son ? com as contribui??es do brasileiro C?sar Lattes. A pesquisa consistiu na elabora??o, aplica??o e avalia??o de uma sequ?ncia did?tica fundamentada na teoria de aprendizagem significativa de David Ausubel

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L'étude de la production des quarks charmés dans les collisions de hautes énergies de noyaux atomiques offre une approche inédite pour l'étude du plasma de quarks et de gluons. La compréhension et la caractérisation de cet état de la matière déconfinée, de prime abord retrouvé dans les systèmes les plus lourds, nécessitent une connaissance fine des systèmes les plus légers, telles que les collisions proton-proton (pp) et proton-plomb (p-Pb). Dans ce manuscrit, nous présentons la mesure de la production des mésons charmés-étranges Ds+, à rapidité centrale, avec les données du run 2 du LHC, recueillies en 2016 par l'expérience ALICE. Deux systèmes sont étudiés : les collisions pp à √s=13 TeV et p-Pb à √sNN=5,02 TeV. La section efficace de production des Ds+, leur abondance relative et leur facteur de modification nucléaire sont mesurés puis comparés à d'autres mesures et à diverses prédictions théoriques. Le résultat p-Pb établit une nouvelle référence pour l'étude des collisions Pb-Pb. / The study of the production of charm quarks in high-energy atomic-nucleus collisions offers an genuine approach for the study of the quark-gluon plasma. The understanding and characterisation of this state of deconfined-matter, at first sight created in heaviest systems, require a fine knowledge of lightest systems, such as proton-proton (pp) and proton-lead (p-Pb) collisions. In this manuscript, we present the measurement of the charm-strange mesons Ds+ production, at central rapidity, with the LHC run 2 data, collected in 2016 with the ALICE experiment. Two systems are studied: pp collisions at √s=13 TeV and p-Pb collisions at √sNN=5.02 TeV. The production cross-section of Ds+, their relative abundance and their nuclear modification factor are measured then compared to other measurements and to various theoretical predictions. The p-Pb result establishes a new reference for the study of Pb-Pb collisions.