<p>Heavy flavor hadrons serve as valuable probes of the transport properties of the quark-gluon plasma (QGP) created in relativistic heavy-ion collisions. In this dissertation, we introduce a comprehensive framework that describes the full-time evolution of heavy flavor in heavy-ion collisions, including its initial production, in-medium evolution inside the QGP matter, hadronization process from heavy quarks to their respective mesonic bound states and the subsequent interactions between heavy mesons and the hadron gas.</p><p>The in-medium energy loss of heavy quarks is studied within the framework of a Langevin equation coupled to hydrodynamic models that simulate the space-time evolution of the hot and dense QGP matter. We improve the classical Langevin approach such that, apart from quasi-elastic scatterings between heavy quarks and the medium background, radiative energy loss is incorporated as well by treating gluon radiation as a recoil force term. The subsequent hadronization of emitted heavy quarks is simulated via a hybrid fragmentation plus recombination model. The propagation of produced heavy mesons in the hadronic phase is described using the ultra-relativistic quantum molecular dynamics (UrQMD) model. Our calculation shows that while collisional energy loss dominates the heavy quark motion inside the QGP in the low transverse momentum (pT) regime, contributions from gluon radiation are found to be significant at high pT. The recombination mechanism is important for the heavy flavor meson production at intermediate energies. The hadronic final state interactions further enhance the suppression and the collective flow of heavy mesons we observe. Within our newly developed framework, we present numerical results for the nuclear modification and the elliptic flow of D mesons, which are consistent with measurements at both the CERN Large Hadron Collider (LHC) and the BNL Relativistic Heavy-Ion Collider (RHIC); predictions for B mesons are also provided.</p><p>In addition, various transport properties of heavy quarks are investigated within our numerical framework, such as the thermalization process of heavy quarks inside the QGP, and how the initial configuration of the QGP as well as its properties affect the final state spectra and the elliptic flow of heavy mesons and their decay electrons. The effects of initial state fluctuations in heavy-ion collisions are also studied and found to enhance the heavy quark energy loss in a (2+1)-dimensional boost invariant scenario. Furthermore, a new set of observables -- heavy-flavor-tagged angular correlation functions -- are explored and found to be potential candidates for distinguishing different energy loss mechanisms of heavy quarks inside the QGP.</p> / Dissertation

O Plasma de Quarks e Glúons (Quark Gluon Plasma ou QGP) criado de forma sistemática em grandes aceleradores de partículas que envolvem colaborações do mundo inteiro, apesar de ter sua descoberta anunciada há bastante tempo ainda apresenta desafios e questões a serem respondidas tanto do ponto de vista experimental como do teórico. O objetivo deste trabalho é estudar a conexão entre as condições iniciais da expansão do QGP (que dependem da interação forte e não são acessíveis ao experimento) com a anisotropia da emissão azimutal das partículas (que por sua vez reflete as condições iniciais e é medida experimentalmente). O modelo hidrodinâmico é descrito inicialmente, com ênfase no programa NeXSPheRIO. Também são apresentadas alguns tipos de observáveis e modelos de condições iniciais (NeXus, MC-KLN e TRENTO). Por fim resultados de simulações para distribuições evento-por-evento do fluxo anisotrópico (facilmente ligadas aos modelos de condições iniciais) são comparadas com dados do LHC e previsões são feitas para a energia mais alta do RHIC. Estas previsões são testadas via a razão $v_2\\{4\\}/v_2\\{2\\}$ para a qual dados existem. / The Quark Gluon Plasma (QGP), created in a systematic way in large particle accelerators which are built by worldwide collaborations, even though its discovery being announced a long time ago it still presents us with challenges and questions to be answered even from the experimental point of view to the theoretical one. The main goal of this work is to study the connection between the initial conditions for the QGP expansion (which depend on strong interactions and are not accesible to the experiments) to the anisotropy in the azimuthal particle emission (which in turn reflects the initial conditions and is measured experimentally). The hydrodynamical model is described initially, with emphasis on the code NeXSPheRIO. Additionally some types of observables and initial condition models (NeXus, MC-KLN and TRENTO) are presented. And at last, results from simulations for event-by-event distributions for the anisotropic flow (easily connected to the initial conditions models) are compared with LHC\'s data and predictions are made for the RHIC\'s top energy. These predictions are tested by the $v_2\\{4\\}/v_2\\{2\\}$ for which data exists.

O Plasma de Quarks e Glúons (Qgp), um meio denso e quente, pode ser produzido em laboratório a partir da colisão entre íons pesados relativísticos. Pode-se estudá-lo a partir da comparação entre jatos reconstruídos em tais eventos e aqueles reconstruídos em colisões próton-próton, uma vez que se espera que os pártons ao atravessarem o Qgp percam energia em função da interação com o meio, o chamado jet quenching. Este trabalho propõe dois novos observáveis no estudo de jatos reconstruídos em colisões entre íons pesados relativísticos: o espectro de jatos quasi-inclusivo e a evolução do espectro de jatos de recuo em função da partícula trigger. Mostra-se que conhecida a função de resolução do momento reconstruído do jato é possível obter o espectro verdadeiro desses observáveis a partir da técnica de deconvolução bayesiana iterativa. A técnica proposta é empregada em eventos de colisões núcleonúcleo realizadas nos aceleradores Rhic e Lhc cujos dados foram coletados pelas colaborações Star e Alice, respectivamente. Os resultados evidenciam a ocorrência do fenômeno de jet queching independentemente do sistema, da energia e da centralidade da colisão em um grande intervalo cinemático. / The Quark-Gluon Plasma (Qgp), a hot and dense medium, can be produced in laboratory by colliding relativistic heavy ion. This medium can be studied by the comparison of jets reconstructed in such events and those reconstructed in proton-proton collisions, once it is expected that partons lose energy when traversing the Qgp due to its interaction with the medium, the so-called jet quenching. This work proposes two new observables: the quasiinclusive jet spectrum and the evolution of the recoil jet spectrum as function of the trigger particle. It is shown that it is possible to obtain those spectra using iterative bayesian unfolding, which requires the resolution function for the reconstructed jet transverse momentum. This technique is applied to Star and Alice data which has been taken at Rhic and Lhc, respectively. The results indicate that jet quenching occurs in a very wide kinematic range, regardless the colliding system, its energy and centrality.

O estudo de teorias de calibre não-Abelianas fortemente acopladas, em especial de aspectos térmicos e fora do equilíbrio, é um problema central para a compreensão da Cromodinâmica Quântica (Quantum Chromodynamics - QCD) - em particular, para entender a evolução do Plasma de Quarks e Glúons (Quark-Gluon Plasma- QGP). A técnica mais promissora, QCD na rede, obteve sucesso ao tratar de fenômenos no vácuo e em equilíbrio térmico, como espectros e termodinâmica, mas enfrenta desafios consideráveis ao lidar com fenômenos fora do equilíbrio. Uma ferramenta adaptada para lidar com problemas envolvendo plasmas fortemente acoplados em tempo real é a dualidade gauge/gravity, que mapeia uma Teoria Quântica de Campos (Quantum Field Theory - QFT) fortemente acoplada em d dimensões em uma teoria de gravitação em d + 1 dimensões, a qual, de modo geral, é mais fácil de ser resolvida. Nesta tese, estudamos diversas aplicações da dualidade gauge/gravity em teorias não-Abelianas fortemente acopladas que modelam qualitativamente o QGP. Nós estudamos o cálculo holográfico do potencial entre um par quark-antiquark pesado (QQ) para dipolos QQ estáticos e se movendo com relação ao plasma, apresentando um formalismo geral para o cálculo da parte real e imaginária para uma grande classe de teorias gravitacionais duais. Um estudo da massa de Debye holográfica, baseado no maior comprimento de correlação de operadores ímpares por transformações de CT, foi empreendido, com aplicações em modelos bottom-up que reproduzem a termodinâmica da teoria de Yang-Mills SU(Nc) pura e da QCD. Para estes modelos, também calculamos vários coeficientes de transporte associados com o transporte de cargas no plasma, como a condutitividade elétrica, a constante de difusão de carga e coeficientes de transporte associados a uma teoria de hidrodinâmica relativística de segunda ordem. / The study of strongly coupled non-Abelian gauge theories, especially concerning their thermal and non-equilibrium aspects, is a central problem for understanding Quantum Chromodynamics (QCD) - in particular, to understand the evolution of the Quark-Gluon Plasma (QGP). The most successful approach, lattice QCD, succeeds in dealing with vacuum and equilibrium phenomena, such as spectra and thermodynamics, but faces a considerable challenge when it comes to with non-equilibrium phenomena. A tool adapted to deal with real time problems in strongly coupled plasmas is the gauge/gravity, which maps a strongly coupled d dimensional Quantum Field Theory (QFT) to a d + 1 dimensional theory of gravity, which, in general, is easier to solve. In this thesis, we study several applications of the gauge/gravity duality to strongly coupled non-Abelian theories which model qualitatively the QGP. We deal with the holographic evaluation of the heavy quark-antiquark (Q Q) potential for static and moving QQ dipoles, presenting a general formalism for the computation of the real and imaginary parts for a large class of dual theories of gravity. A study of the holographic Debye mass, based on the largest screening length of CT-odd operators, is pursued, with applications on bottom-up holographic models that reproduce the thermodynamics of pure SU(Nc) Yang-Mills theory and QCD. For these models, we also compute several transport coefficients associated with charge transport in the plasma, such as the electric conductivity, the charge diffusion constant, and transport coefficients associated with a theory of second order relativistic hydrodynamics.

L'expérience INDRA@GSI permet d'étudier les mécanismes de la réaction 12C+197Au en cinématique directe par l'utilisation du multidétecteur 4p INDRA et de faisceaux de 12C aux énergies relativistes. La source du spectateur de la cible est determinée pour les protons et les fragments légers, séparement de la source de cascade émettant des particules légeres et d'une source de haute energie émettant des fragments approximativement dans le centre de masse. Les spectres de protons en énergie cinétique sont comparés à des combinaisons du modèle de Cascade Intra-Nucléaire de Liège avec des modèles statistiques. Le scénario privilegié associe un processus de cascade avec une multifragmentation statistique. Les températures de pente des fragments determinées par une combinaison de fonctions de Maxwell-Boltzmann mettent en évidence une dépendance en énergie de faisceau, la centralité de la réaction étant donnée par la multiplicité de particules chargées. Les pions, detectés pour la première fois avec INDRA, et les protons rapides présentent une correlation avec le paramètre d'impact mais non avec la production de fragments.

With the use of an incoherent binary nucleon-nucleon collision model of heavy ion collisions for simulating particle production, it is demonstrated that the nuclear modification factors, R_{AA} and R_{CP}, are less than unity for hard scattering in the absence of any nuclear modification effects. The nuclear modification factor R_{dAu} is also shown to approach or exceed unity only if p_T broadening is taken into account. With a simple phenomenological parameter, the mean nucleon energy loss fraction, this model yields particle distributions that are comparable to those of experiment. The nuclear geometry is described by the Glauber model, and particle production is simulated by the PYTHIA event generator.

O estudo de teorias de calibre não-Abelianas fortemente acopladas, em especial de aspectos térmicos e fora do equilíbrio, é um problema central para a compreensão da Cromodinâmica Quântica (Quantum Chromodynamics - QCD) - em particular, para entender a evolução do Plasma de Quarks e Glúons (Quark-Gluon Plasma- QGP). A técnica mais promissora, QCD na rede, obteve sucesso ao tratar de fenômenos no vácuo e em equilíbrio térmico, como espectros e termodinâmica, mas enfrenta desafios consideráveis ao lidar com fenômenos fora do equilíbrio. Uma ferramenta adaptada para lidar com problemas envolvendo plasmas fortemente acoplados em tempo real é a dualidade gauge/gravity, que mapeia uma Teoria Quântica de Campos (Quantum Field Theory - QFT) fortemente acoplada em d dimensões em uma teoria de gravitação em d + 1 dimensões, a qual, de modo geral, é mais fácil de ser resolvida. Nesta tese, estudamos diversas aplicações da dualidade gauge/gravity em teorias não-Abelianas fortemente acopladas que modelam qualitativamente o QGP. Nós estudamos o cálculo holográfico do potencial entre um par quark-antiquark pesado (QQ) para dipolos QQ estáticos e se movendo com relação ao plasma, apresentando um formalismo geral para o cálculo da parte real e imaginária para uma grande classe de teorias gravitacionais duais. Um estudo da massa de Debye holográfica, baseado no maior comprimento de correlação de operadores ímpares por transformações de CT, foi empreendido, com aplicações em modelos bottom-up que reproduzem a termodinâmica da teoria de Yang-Mills SU(Nc) pura e da QCD. Para estes modelos, também calculamos vários coeficientes de transporte associados com o transporte de cargas no plasma, como a condutitividade elétrica, a constante de difusão de carga e coeficientes de transporte associados a uma teoria de hidrodinâmica relativística de segunda ordem. / The study of strongly coupled non-Abelian gauge theories, especially concerning their thermal and non-equilibrium aspects, is a central problem for understanding Quantum Chromodynamics (QCD) - in particular, to understand the evolution of the Quark-Gluon Plasma (QGP). The most successful approach, lattice QCD, succeeds in dealing with vacuum and equilibrium phenomena, such as spectra and thermodynamics, but faces a considerable challenge when it comes to with non-equilibrium phenomena. A tool adapted to deal with real time problems in strongly coupled plasmas is the gauge/gravity, which maps a strongly coupled d dimensional Quantum Field Theory (QFT) to a d + 1 dimensional theory of gravity, which, in general, is easier to solve. In this thesis, we study several applications of the gauge/gravity duality to strongly coupled non-Abelian theories which model qualitatively the QGP. We deal with the holographic evaluation of the heavy quark-antiquark (Q Q) potential for static and moving QQ dipoles, presenting a general formalism for the computation of the real and imaginary parts for a large class of dual theories of gravity. A study of the holographic Debye mass, based on the largest screening length of CT-odd operators, is pursued, with applications on bottom-up holographic models that reproduce the thermodynamics of pure SU(Nc) Yang-Mills theory and QCD. For these models, we also compute several transport coefficients associated with charge transport in the plasma, such as the electric conductivity, the charge diffusion constant, and transport coefficients associated with a theory of second order relativistic hydrodynamics.

O Plasma de Quarks e Glúons (Qgp), um meio denso e quente, pode ser produzido em laboratório a partir da colisão entre íons pesados relativísticos. Pode-se estudá-lo a partir da comparação entre jatos reconstruídos em tais eventos e aqueles reconstruídos em colisões próton-próton, uma vez que se espera que os pártons ao atravessarem o Qgp percam energia em função da interação com o meio, o chamado jet quenching. Este trabalho propõe dois novos observáveis no estudo de jatos reconstruídos em colisões entre íons pesados relativísticos: o espectro de jatos quasi-inclusivo e a evolução do espectro de jatos de recuo em função da partícula trigger. Mostra-se que conhecida a função de resolução do momento reconstruído do jato é possível obter o espectro verdadeiro desses observáveis a partir da técnica de deconvolução bayesiana iterativa. A técnica proposta é empregada em eventos de colisões núcleonúcleo realizadas nos aceleradores Rhic e Lhc cujos dados foram coletados pelas colaborações Star e Alice, respectivamente. Os resultados evidenciam a ocorrência do fenômeno de jet queching independentemente do sistema, da energia e da centralidade da colisão em um grande intervalo cinemático. / The Quark-Gluon Plasma (Qgp), a hot and dense medium, can be produced in laboratory by colliding relativistic heavy ion. This medium can be studied by the comparison of jets reconstructed in such events and those reconstructed in proton-proton collisions, once it is expected that partons lose energy when traversing the Qgp due to its interaction with the medium, the so-called jet quenching. This work proposes two new observables: the quasiinclusive jet spectrum and the evolution of the recoil jet spectrum as function of the trigger particle. It is shown that it is possible to obtain those spectra using iterative bayesian unfolding, which requires the resolution function for the reconstructed jet transverse momentum. This technique is applied to Star and Alice data which has been taken at Rhic and Lhc, respectively. The results indicate that jet quenching occurs in a very wide kinematic range, regardless the colliding system, its energy and centrality.

La Chromodynamique Quantique prédit que la matière chaude et dense produite en collisions d'ions lourds ultra-relativistes, le Plasma de Quarks et de Gluons (QGP), se conduit comme un état déconfiné de quarks et gluons.ALICE est la seule expérience au LHC qui a été conçue et construite pour caractériser la physique du QGP. Le spectromètre à muons, un des détecteurs d'ALICE, est utilisé pour mesurer la production de quarkonia à rapidité en avant.Dans la thèse suivante, l'efficacité des chambres de trajectographie du spectromètre à muons est étudiée durant une année de pris des données. Les résultats obtenus des données réelles sont comparés avec des simulations pour calculer les incertitudes systématiques par rapport aux chambres de trajectographie.Une analyse complète de la production inclusive de J/psi --> mu^+ mu^- dans les collisions Pb-Pb 2011 est également presentée. L' étude inclut l'extraction du signal, normalisation et corrections d'acceptance et d'efficacité. Une partie importante est consacrée à quantifier les incertitudes systématiques liées aux différentes sources. Les résultats, R_{AA} et <p_{T}> , sont comparés avec des expériences précédentes et des modèles théoriques. / Quantum Chromodynamics predicts that the hot and dense matter produced in ultra-relativistic heavy-ion collisions, the Quark Gluon Plasma (QGP), behaves as a deconfined state of quarks and gluons. Since 1980's it was predicted that quarkonia are suppressed due to screening effects in the QGP, making quarkonia a good tool to probe the plasma.ALICE is the only experiment at the LHC that was designed and built to characterize the physics of the QGP. The muon spectrometer, one of the detectors in ALICE, is used to measure the quarkonia production at forward rapidity. In this thesis the efficiency of the tracking chambers of the muon spectrometer is studied along one year of data taking. The results obtained from real data are compared to simulations in order to compute the systematic uncertainties associated to the tracking apparatus.A complete analysis of the inclusive J/psi --> mu^+ mu^- production in the 2011 Pb-Pb collisions is also presented. The study includes the signal extraction, normalization and acceptance times efficiency corrections. An important part is dedicated to the quantify the systematic uncertainties arising from different sources. The resulting R_{AA} and <p_{T}> are compared to previous experiments and also to theoretical models.

In this thesis high-statistics π⁻π⁻ and π⁺π⁺ femtoscopy data are presented for Au+Au collisions at √sNN =2.4 GeV, measured with the High Acceptance Di-Electron Spectrometer HADES located at the heavy-ion synchrotron SIS18 at GSI.Due to space-momentum correlations the technique of intensity interferometry allows only to measure regions of homogeneity where pairs of particles with certain momentum origin. The determination of the space-time extent of the corresponding emission sources is then only possible via a comparison to models.The purpose of this thesis is to provide a multi-differential data set as input for such models and calculations, to draw conclusions from the total spatial and temporal extension of the pion emitting source. More than two billion events of the 45 % most central collisions are analysed. A complex data-driven pair cut is established to account for the close-track deficits in the non-trivial hexagonal geometry of the HADES setup. The correlation function is studied in the longitudinally co-moving system using the Bertsch-Pratt parametrisation. The region of homogeneity, parametrised as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, rapidity, azimuthal emission angle with respect to the event plane, collision centrality, and beam energy. For all centralities and transverse momenta, a geometrical distribution of ellipsoidal shape is found in the plane perpendicular to the beam direction with the larger extension perpendicular to the reaction plane. For large transverse momenta, the corresponding eccentricity approaches the initial eccentricity. The eccentricity is smallest for most central collisions, where the shape is almost circular.Furthermore, a tilt of the source w.r.t. the beam axis is found.The magnitude of the tilt angle of the emission ellipsoid in the reaction plane decreases with increasing centrality and increasing transverse momentum. All source radii increase with centrality, largely exhibiting a linear rise with the cubic root of the number of participants. A substantial charge-sign difference of the source radii is found, appearing most pronounced at low transverse momentum, which is addressed to the central Coulomb potential generated by the electrical charge of the participating nucleons in the collision. The extracted source parameters agree well with a smooth extrapolation of the center-of-mass energy dependence established at higher energies, extending the corresponding excitation functions down towards a very low energy. / In dieser Arbeit werden femtoskopische π⁻π⁻- und π⁺π⁺-Daten mit hoher Statistik präsentiert, welche in Kollisionen von Au+Au bei einer Schwerpunktsenergie von √sNN =2.4 GeV pro Nukleonpaar mithilfe von HADES (Zwei-Elektronen Spektrometer mit hoher Akzeptanz) am Schwerionen-Synchrotron an der GSI gemessen wurden. Aufgrund von Orts-Impuls-Korrelationen können mittels der Methode der Intensitäts-Interferometry nur Homogenitätsbereiche gemessen werden, aus welchen Teilchenpaare mit bestimmten Impuls entspringen. Die Bestimmung der raum-zeitlichen Ausdehnung der entsprechenden Emissionsquelle ist dann nur über die Hinzunahme von Modellvergleichen möglich. Die Absicht dieser Arbeit ist es, einen multi-differenziellen Daten-Satz zur Verfügung zustellen, welcher als Eingabe für solche Modelle und Rechnungen genutzt werden kann, um dann Rückschlüsse auf die absolute räumliche und zeitliche Ausdehnung der Pionen-emittierenden Quelle ziehen zu können. Mehr als zwei Milliarden Ereignisse der 45 % zentralsten Kollisionen werden analysiert. Eine komplexe Daten-basierende Paarselektion wird eingeführt, um die Verluste nah beieinander verlaufender Teilchenspuren innerhalb des nicht-trivialen hexa-geometrischen HADES-Aufbaus zu berücksichtigen. Die Korrelationsfunktion wird im longitudinal mitbewegten Inertialsystem in Bertsch-Pratt-Parametrisierung untersucht. Der als dreidimensionales Ellipsoid parametrisierte Homogenitätsbereich wird in Abhängigkeit von Transversalimpuls, azimuthalem Emissionswinkel relativ zur Reaktionsebene und Rapidität des Paares sowie Zentralität der Kollision und der Strahlenergie untersucht. In allen Zentralitäts- und Transversalimpulsbereichen wird eine geometrische Verteilung mit elliptischer Form innerhalb der auf die Strahlachse bezogenen transversalen Ebene beobachtet, wobei die größte Ausdehnung senkrecht zur Reaktionsebene zeigt. Für große Transversalimpulse stimmt die zugehörige Exzentrizität mit derjenigen der initialen Nukleonenverteilung überein. Die Exzentrizität ist am kleinsten für die zentralsten Kollisionen, bei denen eine fast kreisrunde Form beobachtet wird. Des Weiteren ist eine Neigung der Emissionsquelle relativ zur Strahlachse feststellbar. Der Wert des Neigungswinkels des Ellipsoids innerhalb der Reaktionsebene verringert sich mit zunehmend zentraleren Kollisionen und steigendem Transversalimpuls. Alle Quellradien werden größer mit zunehmender Zentralität und zeigen einen nahezu linearen Anstieg mit der Kubikwurzel der Anzahl der Partizipanten. Ein beträchtlicher Unterschied der Quellradien bezogen auf das Ladungsvorzeichen der Pionen wird beobachtet, welcher am prägnantesten bei kleinen Transversalim\-pulsen auftritt. Dieser wird dem zentralem Coulomb-Potential zugeschrieben, welches durch die elektrische Ladung der an der Kollision teilnehmenden Nukleonen generiert wird. Die extrahierten Quellparameter stimmen gut mit glatten Extrapolationen der Schwerpunktsenergie-Abhängigkeit überein, welche bei höheren Strahlenergien fixiert wurden, und erweitern diese hinab bis zu sehr kleinen Energien.