Submitted by Wagner Maciel Castilho (castilho.w@gmail.com) on 2017-12-05T10:53:57Z No. of bitstreams: 1 TeseWagner.pdf: 4189219 bytes, checksum: dbc77f46b31b8872c5aafe68d8a5b7d0 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2017-12-05T12:38:21Z (GMT) No. of bitstreams: 1 catilho_wm_dr_guara.pdf: 4189219 bytes, checksum: dbc77f46b31b8872c5aafe68d8a5b7d0 (MD5) / Made available in DSpace on 2017-12-05T12:38:21Z (GMT). No. of bitstreams: 1 catilho_wm_dr_guara.pdf: 4189219 bytes, checksum: dbc77f46b31b8872c5aafe68d8a5b7d0 (MD5) Previous issue date: 2017-11-10 / Os fenômenos físicos envolvidos em colisões relativísticas de íons pesados foram estudados utilizando o código hidrodinâmico NeXSPheRIO, com condições iniciais flutuantes evento a evento, caracterizado por tubos de fluxo longitudinais de altas energias. Foram realizadas análises para o espectro de hádrons em função dos momentos transversais pelos cálculos das distribuições de partículas em sete janelas de centralidade de colisão, de acordo com dados publicados pela Colaboração STAR. A coletividade da matéria nuclear formada durante as colisões foi investigada em termos de correlações azimutais entre hádrons. Verificou-se que as estruturas da correlação dependem do momento transversal e da centralidade. Tais estruturas são atribuídas à interação entre um fundo dependente da centralidade e as flutuações de evento a evento na multiplicidade. Como resultado, as correlações observadas são apresentadas por um duplo pico na região do away-side que mudam continuamente para um pico único sob certas circunstâncias. Em termos do modelo do tubo periférico, o fundo é dominado pelo fluxo elíptico que aumenta com a descentralização. Pelos cálculos numéricos, a anisotropia do sistema é estudada quanto aos coeficientes de fluxo harmônico até a quarta ordem, de acordo com os dados da colaboração PHENIX. A anisotropia do fundo contribui para as correlações entre hádrons e pôde ser avaliada pelo método ZYAM. Após sua subtração na produção do sinal de correlação próprio, a estrutura de correlação resultante é uma função da centralidade, plano de evento e do momento transverso de acordo com os dados das colaborações PHENIX e STAR. Mostrou-se que a estrutura do duplo pico no away-side muda continuamente para um pico único com a redução na centralidade. Além disso, em relação à dependência do plano de eventos, a estrutura de duplo pico no away-side evolui para um pico único à medida que o ângulo azimutal das partículas gatilho se move do plano para o da direção fora do plano de eventos. Também foi mostrado que a estrutura resultante do away-side pode ser sensível ao esquema detalhado pelo método ZYAM, particularmente, a subtração do terceiro coeficiente harmônico. Por último, mas não menos importante, a magnitude da correlação diminuiu com o aumento do momento transversal das partículas associadas. Nossas análises apresentaram um acordo razoável com os dados experimentais publicados pela colaboração PHENIX e STAR do RHIC / The physical phenomena involved in relativistic heavy-ion collisions were studied using a hydrodynamic code, NeXSPheRIO, with event-by-event fluctuating initial conditions featured by high-energy longitudinal flux tubes. Analyses were carried out for hadron spectrum as a function of the transverse momentum by the calculations of particle distributions in seven collision centrality windows, according to the data published by the STAR Collaboration. Also, the collectivity of the nuclear matter formed during the collisions was investigated in terms of dihadron azimuthal correlations. The correlation structures were found to be dependent on the transverse momentum and centrality. They are attributed to the interplay between the centrality dependent background and the eventby-event multiplicity fluctuations. As a result, the observed correlations are featured by a double-peak in the away-side region that continuously change to a single peak under certain circumstances. In terms of the peripheral tube model, the background is dominated by the elliptic flow which increases with decreasing centrality. By numerical calculations, the anisotropy of the system is studied regarding the harmonic flow coefficients up to fourth order, in accordance with the existing RHIC data. The background anisotropy contributes to the dihadron correlations, and can be evaluated by the ZYAM method. After it is subtracted from the proper correlation yields, the resultant correlation structure is a function of centrality, event plane and transverse moment, in accordance with the data from the PHENIX and STAR Collaborations. It was shown that the double-peak structure in the away-side continually changes to a single peak as centrality decreases. In addition, concerning the event plane dependence, the double-peak structure in the away-side evolves into a single peak as the azimuthal angle of the trigger particles moves from the in-plane to the out-of-plane direction. It was also shown that the resultant away-side structure can be sensitive to the detailed schemes of the ZYAM method, particularly, to the subtraction of the third harmonic coefficient. Last but not least, the magnitude of the correlation was found to decrease with increasing transverse moment of the associated particles. Our analyses manifestly presented a reasonable agreement with the experimental data published by the PHENIX and STAR Collaborations

O objetivo desse trabalho é estudar aplicações da correspondência AdS/CFT na descrição de plasmas fortemente acoplados similares ao plasma de quarks e glúons (PQG) produzido em colisões de íons pesados no RHIC e no LHC. O projeto está articulado em duas partes. Inicialmente estudamos como alguns observáveis, como a taxa de produção de fótons e diléptons, são afetados por anisotropias espaciais presentes no plasma. Isso é importante porque o PQG produzido em experimentos do mundo real tipicamente começa em configurações de alta anisotropia, que depois evoluem para configurações isotrópicas. Para modelar a anisotropia a acoplamento forte fizemos uso de uma solução de buraco negro de supergravidade do tipo IIB encontrada recentemente em arXiv:1105.3472/hep-th. Como segunda direção de pesquisa e novamente focando em aplicações da correspondência AdS/CFT na descrição do PQG, investigamos teorias de gravidade de Lovelock, que são generalizações naturais da teoria de relatividade geral de Einstein. Essas teorias contém termos com derivadas de ordem superior ao mesmo tempo que mantém equações do movimento de segunda ordem, e por isso constituem uma arena ideal para começar a entender como termos de derivada de ordem superior afetam vários observáveis físicos do plasma. / The aim of this work is to study applications of the AdS/CFT correspondence to strongly coupled plasmas similar to the quark-gluon plasma (QGP) produced in heavy ion collisions at RHIC and LHC. The project is articulated in two parts. Initially, we will study how some observables, such as photon and dilepton production rates, are affected by spatial anisotropies present in the plasma. This is important, since the QGP produced in real world experiments generically starts in highly anisotropic configurations, which later evolve towards isotropy. To model anisotropy at strong coupling we will make use of an anisotropic black hole solution of type IIB supergravity which has been recently obtained in arXiv:1105.3472/ hep-th. As a second direction of research and again focusing on applications of the AdS/CFT correspondence to the QGP, we will investigate Lovelock theories of gravity, which are natural generalizations of Einsteins general relativity. These theories contain higher derivative terms, while maintaining the equations of motion of second order, and constitute an ideal arena where to start understanding how higher derivative corrections affect various physical observables of the plasma.

A supressão da produção do méson J/Ψ em colisões de íons pesados tem sido apontada como um sinal da formação de um estado desconfinado da matéria - o Plasma de Quarks e Glúons. Este sinal, por em, não e inequívoco e muitos modelos, que não assumem a formação do plasma, podem descrever igualmente bem os resultados da colaboração NA50, no CERN, que apontou uma supressão anômala, não explicada pela absorção nuclear, nas colisões mais centrais entre íons de chumbo. De modo geral, estes modelos, considerando ou não a formação do plasma, procuram explicar os resultados experimentais através de mecanismos que causam a supressão no estado final da colisão, isto e, mecanismos que agem sobre as partículas produzidas na colisão. Por outro lado, para núcleos pesados e em processos envolvendo altas energias, as distribuições partônicas nucleares são alteradas em relação as distribuições para nucleons livres. Estas alterações ocorrem devido ao fato das dimensões do nucleon serem um limite geométrico para o crescimento das distribuições - seu vínculo de unitariedade - pois o meio nuclear, em altas energias, apresenta uma alta densidade partônica. A existência deste vínculo de unitariedade requer modificações das distribuições partônicas, o que deve ser considerado nos cálculos das seções de choque nucleares. Tais modificações afetam a produção de hádrons no estado final, diminuindo sua taxa de produção. Nesse trabalho, investigamos a inclusão dos efeitos de alta densidade nas distribuições partônicas para o tratamento da supressão de J/Ψ em colisões envolvendo alvos nucleares. Estes efeitos são decorrentes do aumento da distribuição de glúions na região de pequeno x (altas energias). A evolução DGLAP, que considera apenas a emissão de pártons, prevê um crescimento ilimitado da distribuição de glúons nesta região, quebrando assim o vínculo da unitariedade. Por isso, o mecanismo de recombinação partônica passa a contribuir para restaurar a unitariedade. Estes efeitos de recombinação, basicamente, são tratados como os efeitos de alta densidade referidos nesse trabalho, alterando as distribuições partônicas nucleares. Utilizamos processos próton-núcleo para estimar a magnitude destes efeitos, uma vez que estes processos não apresentam um meio nuclear tão denso quanto o proporcionado por colisões núcleo-núcleo. Esta premissa torna os processos próton-núcleo testes mais confiaveis para a investigação dos efeitos de alta densidade. Analisamos em especial a razão entre as taxas de produção do méson J/Ψ e do par de léptons, via processo Drell- Yan, uma vez que este observável e utilizado para apontar a supressão na produção de J/Ψ . Estendemos esta análise para processos núcleo-núcleo, onde novos mecanismos de supressão, entre eles a formação do Plasma de Quarks e Glúons são esperados. Os resultados aqui apresentados mostram que a inclusão dos efeitos de alta densidade introduz uma supressão adicional na produção de J/Ψ , que se torna mais significativa com o aumento da energia do processo. Nossa conclusão e, portanto, que estes efeitos devem ser incorporados na análise deste sinal em experimentos realizados em RHIC e LHC.

Orientador: Jun Takahashi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-19T21:22:39Z (GMT). No. of bitstreams: 1 Chinellato_DavidDobrigkeit_D.pdf: 12088648 bytes, checksum: c79560f4593e813870fc0e788aadf075 (MD5) Previous issue date: 2012 / Resumo: Neste trabalho, estudamos a produção de hádrons estranhos em colisões próton-próton (pp) a energias de (s)^(1/2)= 7 TeV medidas pelo experimento ALICE no acelerador LHC. São resentadas medidas inéditas das taxas de produção em rapidez central do méson (K) também dos bárions ?,? e O- e suas antipartículas correspondentes. As taxas totais de produção excedem significativamente as previsões de modelos que utilizam a Cromodinâmica Quântica Perturbativa (pQCD). Em particular, comparamos as medidas com previsões do simulador de eventos PYTHIA, onde é observado que as previsões concordam com as medidas apenas para momentos transversais (Pt) acima de 6- 7 GcV / c. Este resultado indica que os processos de primeira ordem não-nula implementados no PYTHIA estão bem ajustados, mas a implementação de um cálculo que descreva os dados em baixo Pt ainda é um problema em aberto. Os resultados aqui apresentados devem contribuir para melhorar o entendimento dos mecanismos de produção de partículas na região de baixo Pt¿ Colisões pp são também utilizadas como referência para colisões nucleares de diferentes multiplicidades no estudo da formação do Quark-Gluon Plasma (QGP). Em particular, o aumento da produção de estranheza é considerado um importante observável do QGP. Neste contexto, estudamos a dependência da produção de partículas estranhas com a multiplicidade de partículas carregadas e comprovamos que não há indício de aumento da produção relativa de estranheza cm eventos pp. Isto é um importante resultado, pois complementa os estudos que consideram a possibilidade de formação de QGP em colisões pp / Abstract: In this work, we study the production of strange hadrons in proton-proton (pp) collisions at energies of (s)^(1/2)= 7 TeV measured by the ALICE experiment at the LHC. We present the first measurements of particle yields at central rapidities for the (K)meson as well as for the ?, ? e O- baryon and their antiparticles. Total particle production rates exceed predictions by models that use Perturbative Quantum Chromodynamics (pQCD). In particular, we compare our measurements to predictions by the PYTHIA event generator and find that predictions agree with data only at transverse momenta (Pt) higher than 6- 7 GeV / c. This result indicates that the leading order processes implemented in PYTHIA are well adjusted, but the implementation of a calculation that describes the data at low Pt is still an open issue. The results presented here should contribute to improve our understanding of particle production mechanisms at low Pt ¿ Proton-proton collisions are also used as a reference for nuclear collisions of different multiplicities in the study of Quark-Gluon Plasma (QGP) formation. The increase of strangeness production is considered an important observable of the QGP. In this context, we study the dependence of strange particle production with charged particle multiplicity and find that there is no indication of an increase strangeness production rate in pp collisions. This is an important result that contributes to the studies that consider the possibility of QGP formation in pp collisions / Doutorado / Física / Doutor em Ciências

La chromodynamique quantique (QCD) prédit l'existence d'un nouvel état de la matière : le plasma de quarks et de gluons (PQG). Celui-ci aurait existé dans les premiers instants suivant le Big Bang et peut en principe être produit sous les conditions extrêmes de température et de densité atteintes lors de collisions d'ions lourds à haute énergie (au LHC par exemple). Un des marqueurs de sa présence est la suppression des quarkonia (états liés de quark/antiquark lourds), caractérisée par une production inférieure de ces états dans les collisions d'ions lourds relativement aux collisions proton-proton où le PQG ne pourrait être créé. Cette suppression a bien été observée expérimentalement, mais l'évolution de ses tendances aux énergies du RHIC et du LHC est un véritable défi qui requiert une meilleure compréhension théorique. La présente thèse a pour but d’étudier l’évolution en temps réel de paires corrélées de quark/antiquark lourds considérées comme des systèmes quantiques ouverts en interaction permanente avec un PQG en refroidissement. Explicitement, l'interaction continue entre le milieu et les degrés de liberté internes de la paire est obtenue par 1) un écrantage de couleur dit « de Debye » dû à la présence de charges de couleur dans leur voisinage et 2) des mécanismes de fluctuation/dissipation qui reflètent les collisions permanentes. Cela mène à une image dynamique et continue de la dissociation des quarkonia, de leur recombinaison et des transitions entre états liés. L'étude est transversale à différents cadres théoriques : semi-classique, quantique et quantique des champs. Les prédictions du modèle sont comparées aux résultats expérimentaux et aux résultats d'autres modèles théoriques. / The theory of quantum chromodynamics (QCD) predicts the existence of a new state of matter: the Quark-GluonPlasma (QGP). The latter may have existed at the first moments of the Universe following the Big Bang and can be, in theory, re-produced under the extreme conditions of temperature and density reached in high energy heavy ion collisions (at the LHC for instance). One of the QGP observables is the suppression of the quarkonia (heavy quark/antiquark bound states), characterised by a smaller production of these states in heavy ion collisions in comparison to proton-protoncollisions, in which no QGP production would be possible. This suppression has indeed been observed experimentally, but the puzzling evolution of its trend from RHIC to LHC energies requires a better theoretical understanding. The present thesis aims at studying the real-time evolution of correlated heavy quark/antiquark pairs described as open quantum systems which permanently interact with a cooling QGP. More explicitly, the continuous interaction between the medium and the pair internal degrees of freedom is obtained through 1) a temperature dependent color screening (“Debye” like) due to color charges in the irvicinity and 2) some fluctuation/dissipation mechanisms reflecting the continuous collisions. It leads to a dynamical and continuous picture of the dissociation, recombination and possible transitions to other bound states. This investigation is at the crossroads of different theoretical frameworks: semi-classic, quantum and quantum fields. The deduced predictions are compared to experimental data and to the results of other theoretical models.

Les collisions d'ions lourds ultra-relativistes sont considérées comme un outil unique pour produire, enlaboratoire, un milieu chaud et dense interagissant fortement, le Plasma de Quarks etde Gluons (PQG). Cette thèse est dédiée à l’étude de deux sondes, les J/ψ et les bosons Z, qui peuvent aider àatteindre une meilleure compréhension des propriétés du PQG.Dans les collisions d’ions lourds, il existe une observable importante pour étudier la formation du PQG, c’est lamesure de la production des J/ψ. L’importance des différents effets qui peuvent augmenter ou supprimer cetteproduction varie avec l’énergie de la collision. Dans cette thèse, la production des J/ψ est mesurée avec lescollisions Pb-Pb à √sNN =5.02 TeV, en utilisant principalement le spectromètre à muons du détecteur ALICE. Lefacteur de modification nucléaire des J/ψ est présenté en fonction de la centralité des collisions, la rapidité etl’impulsion transversale (pT). En outre, les résultats sur le pT moyen du J/ψ sont présentés. La comparaison entreles résultats expérimentaux et divers calculs théoriques suggère que la production du J/ψ est affectée dans le milieupar deux processus concurrents : le dissociation et le régénération.Dans les collisions d’ions lourds, l'état initial de la collision peut aussi affecter les résultats, en l'absence deformation du PQG. La compréhension et la quantification des tels effets est crucial pour les séparer de ceuxprovoqués par la présence du PQG. Un de ces effets est la modification nucléaire des fonctions de distribution despartons (PDFs). La mesure de production du boson Z dans les collisions d’ions lourds est un outil puissant pourétudier la modification nucléaire des PDFs car il n’est pas affectés par la présence d'une matière en forteinteraction. La seconde partie de cette thèse est dévolue à la mesure de la production des bosons Z, pour lapremière fois dans ALICE, avec les collisions p-Pb et Pb-Pb à √sNN =5.02 TeV. Dans les collisions Pb-Pb où laprécision de la mesure est plus élevée, l'accord entre les données et des calculs théoriques est meilleur lorsque cesderniers prennent en compte la modification nucléaire des PDFs. / Ultra relativistic heavy-ion collisions are considered as a unique tool to produce, in the laboratory, thehot and dense strongly-interacting medium, the Quark-Gluon Plasma (QGP). This thesis is dedicated to the studyof two powerful probes, the J/ψ and Z-boson, that can help reaching a better understanding of the properties of theQGP.An important observable to study the QGP formation in heavy-ion collisions is the measurement of the J/ψproduction. The sizes of the different effects that can enhance or suppress this production vary with the collisionenergy. In this thesis, the J/ψ production is measured in Pb-Pb collisions at √sNN = 5.02 TeV using mainly themuon spectrometer of the ALICE detector. The J/ψ nuclear modification factor is presented as a function ofcollision centrality, rapidity and transverse momentum (pT). In addition, results on the J/ψ average pT and squaredaverage pT are also obtained. The comparison between the results and various theoretical calculations suggests thatthe J/ψ production is affected in the medium by an interplay between dissociation and regeneration mechanisms.In heavy-ion collisions, the initial state of the collision can affect the results even in the absence of the QGP.Understanding and quantifying such effects is crucial in order to separate them from the ones caused by thepresence of the QGP. One of these effects is the nuclear modification of the parton distribution functions (PDFs).The measurement of Z-boson production in heavy-ion collisions is a powerful tool to study the nuclearmodification of PDFs since it is not affected by the presence of the strongly-interacting medium. The second partof this thesis is devoted to measure the Z-boson production, for the first time with ALICE, in p-Pb and Pb-Pbcollisions at √sNN = 5.02 TeV. In Pb-Pb collisions where the precision of the measurement is higher, the agreementbetween data and theoretical calculations is better when the latter take into account the nuclear modification of thePDFs.

Les collisions d’ions lourds à haute énergie du grand collisionneur de hadrons, permettent d'étudier les propriétés de la matière nucléaire et de produire l'état chaud et dense de la matière déconfinée connu sous le nom de plasma de quarks et de gluons (QGP). Afin d'étudier les effets dus à la matière nucléaire dans les collisions d'ions lourds, la production de deux sondes dures importantes est étudiée dans cette thèse: les bosons W et les charmonia (mésons J/ψ et ψ(2S)).Les effets de la matière nucléaire froide, associés à la modification nucléaire des fonctions de distribution des partons (PDF), peuvent être caractérisés en étudiant la formation des bosons W dans les collisions d'ions lourds. En effet, la production des bosons W est déterminée par la diffusion dure initiale, puisque ces bosons n'interagissent pas fortement avec le milieu induit par la collision. L'analyse de la production des bosons W dans les collisions p-Pb à sqrt(s[NN]) = 8,16 TeV avec le détecteur CMS est présentée dans la première partie de cette thèse. Les résultats sont en bon accord avec les calculs des PDFs incluant les modifications nucléaires, alors qu'ils excluent significativement l'hypothèse de nucléons libres, pour des fractions d’impulsion x petite. Puisque les mesures sont plus précises que les calculs des modèles, les résultats des bosons W ont le potentiel de contraindre les paramétrisations des PDF nucléaires, ce qui pourrait améliorer notre compréhension des effets des PDF sur d'autres sondes dures, comme les charmonia.La production des charmonia est sensible à la formation et à l'évolution du milieu forte interaction formé lors de collisions d'ions lourds, en faisant ainsi une excellente sonde du QGP. La suppression ou l'augmentation des différents états du charmonium sont considérées comme des signatures de la présence du QGP. Dans cette thèse, la production prompte et non-prompte des mésons J/ψ est mesurée dans des collisions Pb-Pb à sqrt(s[NN]) = 5,02 TeV. De plus, la modification des mésons ψ(2S) par rapport aux mésons J/ψ est mesurée pour le même système de collision. Le facteur de modification nucléaire des charmonia est déterminé en fonction de la centralité, de la rapidité et de l'impulsion transverse pT. La production des mésons J/ψ prompts est supprimée dans les collisions Pb-Pb par rapport aux collisions p-p normalisés par le nombre de collisions binaires, bien qu'une suppression plus faible soit observée à 3 < pT < 6,5 GeV/c dans les collisions centrales. La production des quarks b, sondés par les charmonia non prompts, est également supprimée dans toute la région cinématique mesurée, et une plus faible suppression est observée à haut pT. En ce qui concerne les mésons ψ(2S), ils se révèlent plus fortement supprimés que les mésons J/ψ dans les collisions Pb-Pb. / Heavy ions are collided at high energies at the Large Hadron Collider, allowing to study the properties of nuclear matter and to produce the hot and dense state of deconfined matter known as the Quark-Gluon Plasma (QGP). In order to probe the nuclear matter effects present in heavy-ion collisions, this thesis study the production of two important hard probes: W bosons and charmonia (J/ψ and ψ(2S) mesons).The cold nuclear matter effects, associated to the nuclear modification of the parton distribution functions (PDFs), can be characterised by studying the formation of W bosons in heavy-ion collisions. The production of W bosons represents an important tool to asses the PDF modifications, which impact the initial hard scattering, since these bosons do not interact strongly with the collision-induced medium. The analysis of the W-boson production in p-Pb collisions at sqrt(s[NN]) = 8.16 TeV with the CMS detector is presented in the first part of this thesis. The results are in good agreement with PDF calculations including nuclear modifications, while they strongly disfavour the free-nucleon hypothesis at small momentum fractions x. Since the measurements are more precise than the model calculations, the W-boson results have the potential to constrain the nuclear PDF parametrisations, which could eventually improve our understanding of the PDF effects on other hard probes, such as charmonia.The production of charmonia is sensitive to the formation and evolution of the strongly-interacting medium formed in heavy-ion collisions, thus making of it an excellent probe of the QGP. The suppression or enhancement of the different charmonium states is considered a signature of the presence of the QGP. In this thesis, the production of prompt and nonprompt J/ψ mesons is measured in Pb-Pb collisions at sqrt(s[NN]) = 5.02 TeV. In addition, the modification of the ψ(2S) mesons relative to J/ψ mesons is reported for the same collision system. The nuclear modification factor of charmonia is determined as a function of centrality, rapidity and transverse momentum pT. The production of prompt J/ψ mesons is suppressed in Pb-Pb collisions compared to binary-scaled p-p collisions, although a weaker suppression is observed at 3 < pT < 6.5 GeV/c in central Pb-Pb collisions. The production of b quarks, probed by the nonprompt charmonia, are also suppressed over the full kinematic region measured, and a reduced suppression is observed at high pT. Regarding the ψ(2S) mesons, they are found to be more strongly suppressed than J/ψ mesons in Pb-Pb collisions.

Les collisions d’ions lourds ultrarelativistes ont pour objectif principal l'étude des propriétés de la matière nucléaire soumise à températures et densités d'énergie extrêmes. La chromodynamique quantique (QCD) prédit, dans ces conditions, l’existence d’une nouvelle phase de la matière dans laquelle les constituants des hadrons sont déconfinés en un plasma de quarks et gluons (QGP). Les saveurs lourdes (charme et beauté) sont produites lors de processus durs aux premiers instants des collisions, avant de traverser le milieu. Par conséquent, la mesure des quarkonia (mésons cc et bb) est particulièrement intéressante pour l'étude du QGP : leur dissociation, due notamment à l’écrantage de couleur, est sensible à la température initiale du système. Les mesures effectuées au SPS et RHIC ont permis de mettre en évidence plusieurs caractéristiques du milieu produit, mais ont aussi laissé plusieurs questions sans réponse. Avec une énergie 14 fois supérieure à celle du RHIC, l’accélérateur LHC (Large Hadron Collider) au CERN, entré en fonctionnement fin 2009, a ouvert une nouvelle ère pour l'étude des propriétés du QGP. ALICE (A Large Ion Collider Experiment) est une des quatre grandes expériences fonctionnant auprès du LHC et dont le but principal est l'étude du plasma de quarks et gluons produit dans les collisions d'ions plomb à une énergie de 2.76 TeV par nucléon. Elle enregistre aussi des collisions pp afin de fournir la référence indispensable pour l'étude des collisions noyau-noyau et proton-noyau et de tester les calculs perturbatifs de QCD dans la région des faibles valeurs de la variable d'échelle x de Bjorken. Les quarkonia, ainsi que les saveurs lourdes ouvertes et les mésons légers, sont mesurés dans ALICE suivant leur mode de désintégration muonique avec le spectromètre à muons situé à petit angle polaire. Il est constitué d'un ensemble d’absorbeurs, d’un dipôle chaud, de cinq stations de trajectographie (Muon Tracking) et de deux stations de déclenchement (Muon Trigger). Le travail présenté dans cette thèse a été réalisé de 2011 à 2013 pendant les premières années de prise de données dans l’expérience ALICE. Après une introduction à la physique des ions lourds à hautes énergies et une description du setup expérimental, une étude des performances du Muon Trigger en Pb-Pb est proposée. En particulier, la stabilité dans le temps du détecteur et son efficacité de fonctionnement sont contrôlées. Le cluster size, correspondant au nombre moyen de voies adjacentes touchées par particule détectée, est étudié en fonction des différents variables. Les valeurs expérimentales sont comparées à des simulations afin de fournir une paramétrisation de cet effet. Finalement, la production du méson Ç en collisions Pb-Pb est analysée en détail et comparée à celle en collisions pp à la même énergie. Les résultats obtenus sont comparés aux mesures du J/ψ par ALICE, aux mesures par CMS et à des prédictions de modèles théoriques. / The main goal of ultrarelativistic heavy-ion collisions is the study of the properties of the matter at very high temperatures and energy densities. Quantum chromodynamics (QCD) predicts in these conditions the existence of a new phase of the matter whose components are deconfined in a Quark-Gluon Plasma (QGP). Heavy quarks (charm e bottom) are produced in the first stages of the collisions, before to interact with the medium. Therefore, the measurement of the quarkonia (cc and bb mesons) is of particular interest for the study of the QGP: their dissociation mainly due to the colour screening is sensible to the initial temperature of the medium. Previous measurements at the SPS and RHIC allowed to understand some characteristics of the system produced, but they also opened many questions. With an energy 14 times higher than RHIC, the LHC (Large Hadron Collider) at CERN opened a new era for the study of the QGP properties. ALICE (A Large Ion Collider Experiment) is the LHC experiment fully dedicated to the study of the Quark-Gluon Plasma produced in Pb-Pb collisions at an energy of 2.76 TeV per nucleon. The experiment also participates to the proton-proton data taking in order to obtain the fundamental reference for the study of ion-ion and proton-ion collisions and for testing the predictions at very small Bjorken-x values of the perturbative QCD. Quarkonia, D and B mesons and light vector mesons are measured at forward rapidity by a Muon Spectrometer exploiting their (di)muonic decay. This detector is composed of a front absorber, a dipole magnet, five stations of tracking (Muon Tracking) and two stations of trigger (Muon Trigger). The work presented in this thesis has been carried out from 2011 to 2013 during the first period of data taking of ALICE. After a detailed introduction of the heavy-ion physics and a description of the experimental setup, the performance of the Muon Trigger in Pb–Pb collisions are shown. A particular attention is devoted to the stability of the detector during the time and to the trigger effectiveness. Moreover, the cluster size, corresponding to the number of adjacent strips hit by a particle, is studied as a function of different variables. The experimental results will be compared to simulations in order to obtain a good parametrization of this phenomenon. Finally, the Ç production in Pb-Pb collisions is carefully analysed and compared to that in pp collisions at the same energy. The results are then compared to the J/ψ measurements obtained by ALICE, to the CMS results and to some theoretical predictions.

Heavy-ion collisions are a powerful tool to study hot and dense QCD matter, the so-called Quark Gluon Plasma (QGP). Since heavy quarks (charm and beauty) are dominantly produced in the early stages of the collision, they experience the complete evolution of the system. Measurements of electrons from heavy-flavour hadron decay is one possible way to study the interaction of these particles with the QGP. With ALICE at LHC, electrons can be identified with high efficiency and purity. A strong suppression of heavy-flavour decay electrons has been observed at high $p_{m T}$ in Pb-Pb collisions at 2.76 TeV. Measurements in p-Pb collisions are crucial to understand cold nuclear matter effects on heavy-flavour production in heavy-ion collisions. The spectrum of electrons from the decays of hadrons containing charm and beauty was measured in p-Pb collisions at $\\sqrt = 5.02$ TeV. The heavy flavour decay electrons were measured by using the Time Projection Chamber (TPC) and the Electromagnetic Calorimeter (EMCal) detectors from ALICE in the transverse-momentum range $2 < p_ < 20$ GeV/c. The measurements were done in two different data set: minimum bias collisions and data using the EMCal trigger. The non-heavy flavour electron background was removed using an invariant mass method. The results are compatible with one ($R_ \\approx$ 1) and the cold nuclear matter effects in p-Pb collisions are small for the electrons from heavy-flavour hadron decays. / Colisões de íons pesados relativísticos é uma ferramenta poderosa para se estudar o plasma de quarks e glúons (QGP). Quarks pesados ({\\it charm} e {\\it beauty}) são produzidos nos estágios iniciais da colisão e participam da evolução completa do sistema. Medidas de elétrons provenientes de quarks pesados é uma das possíveis formas de se estudar a interação destas partículas com o QGP. Utilizando o detetor ALICE do LHC, elétrons podem ser identificados com alta eficiência e boa pureza. Uma forte supressão de elétrons provenientes de quarks pesados foi observada em alto $p_$ em colisões de Pb-Pb a 2.76 TeV. Medidas do mesmo observável em colisões p-Pb são cruciais para se entender os efeitos da matéria nuclear fria na produção de tais partículas. O espectro de elétrons provenientes de hádrons que contêm {\\it charm} ou {\\it beauty} foi medido em colisões p-Pb a $\\sqrt = 5.02$ TeV. Os elétrons foram identificados utilizando o {\\it Time Projection Chamber} (TPC) e o {\\it Electromagnetic Calorimeter} (EMCal) do detetor ALICE, no intervalo de momento transversal de $2 < p_ < 20$ GeV/c. As medidas foram realizadas utilizando dois diferentes conjunto de dados: colisões de mínima tendenciosidade ({\\it minimum bias (MB)}) e colisões tomadas utilizando o trigger do EMCal. Os elétrons de fundo foram removidos utilizando um método de massa invariante. Os resultados são compatíveis com a unidade ($R_ \\approx$ 1) e os efeitos da matéria nuclear fria são pequenos para elétrons provenientes de quarks pesados.

Les conditions extrêmes de température et de densité d'énergie créées lors des collisions d'ions lourds ultra-relativistes au sein du Grand collisionneur de hadrons (LHC) fournissent une occasion unique d'étudier les propriétés de la matière. Une transition de phase de la matière hadronique vers un milieu déconfiné de quarks et de gluons (PQG) est prédite par la chromodynamique quantique et des efforts théoriques et expérimentaux considérables ont été investis pour étudier ses propriétés. Parmi les sondes éminentes du PQG, les quarks lourds jouent un rôle prépondérant car ils sont créés lors des processus durs initiaux, avant la formation du PQG, et leur nombre est conservé durant les phases partoniques et hadroniques de la collision. Les états liés de quarks lourds– quarkonium (charmonium pour cc et bottomonium pour bb), constituent des sondes remarquables du milieu. Les observations expérimentales de quarkonia aux énergies du LHC dans les collisions A-A sont reproduites au travers de deux mécanismes antagonistes : la suppression séquentielle, proposée très tôt comme signature du PQG, et la (re)génération de quarkonia par (re)combinaison de quarks déconfinés. Cependant des incertitudes importantes sont associées aux prédictions théoriques et de nombreuses inconnues demeurent. L'anisotropie azimuthale de l'espace des moments (désignée sous le terme de flot elliptique, v2) de la production de charmonium devrait permettre d'avoir une meilleure vue d'ensemble et de contraindre davantage les paramètres des modèles théoriques. Si les quarks charmés se (re)combinent en paires cc, les J/ψ produits devraient hériter de leur flot. Les études précédentes ont montré des premiers signes d'un v2positif du J/ψ dans les collisions Pb-Pb à √sNN=2.76TeV. Cette thèse porte sur la mesure de l'anisotropie azimuthale du J/ψ dans les collisions Pb-Pb à√sNN=5.02TeV où une (re)combinaison légèrement plus importante est prédite par rapport aux énergies inférieures et une augmentation statistique d'un facteur 3 a été enregistrée. L'étude du flot elliptique du J/ψ fournit des informations clés sur la magnitude et la dynamique des mécanismes de suppression et de (re)génération de charmonia. Par ailleurs elle offre un regard unique sur l'évolution et les interactions des quarks charmés au sein du milieu en expansion. / Extreme temperatures and energy densities produced in ultra-relativistic heavy-ion collisions at the Large Hadron Collider provide a unique opportunity to study the properties of matter. A phase transition of the hadronic matter to a deconfined medium of quarks and gluons, the Quark-Gluon Plasma (QGP), is predicted by Quantum Chromodynamics and considerable theoretical and experimental efforts have been invested to study its properties. Among the prominent probes of the QGP, heavy quarks play a crucial role since they are created in primary hard-scattering processes, before the QGP formation, and their number is conserved throughout the partonic and hadronic phases of the collision. Bound states of heavyquarks – quarkonium (charmonium for cc and bottomoniumbb) provide remarkable probes of the medium. At LHC energies, experimental observations of quarkonium in A-Acollisions are reproduced through two antagonist mechanisms: a sequential suppression of the quarkonium states, early suggested as a signature of the QGP, and quarkonium (re)generation by (re)combination of deconfined quarks. However, theoretical predictions carry large uncertainties and many unknows remain. The momentum space azimuthal anisotropy of charmonium production (referred as elliptic flow v2) should help to clarify the picture and to constrain the model parameters. If charm quarks (re)combine in the medium into cc pairs, the J/ψ originating from (re)combination should inherit their flow. Previous studies have shown first hints of a positive J/ψ v2 in Pb-Pb collisions at √sNN=2.76TeV. This thesis focuses on the measurement of J/ψ azimuthal anisotropy in Pb-Pb collisions at √sNN=5.02TeV where a slightly stronger (re)generation component is predicted with respect to lower collision energies, and a factor of 3more data were collected. The study of J/ψ v2 provides important information on the magnitude and dynamics of charmonium suppression and (re)generation mechanisms. In addition, it offers a unique insight on charm quark evolution and interactions in the expanding medium.