Cette thèse répond une étude de la η c (1S) d'état de charmonium utilisant désintégrations à l'état final proton-antiproton à l'expérience LHCb. La section efficace de production du méson η c dans les interactions parton et dans les désintégrations b-hadrons sont signalés. La production de l'état η c (1S) est mesurée par la désintégration de ppbar avec le détecteur LHCb, en utilisant une luminosité intégrée de 0,7 fb⁻¹ accumulé à 7 TeV l'énergie de centre de masse en 2011, et une luminosité intégrée de 2 fb⁻¹ accumulé à 8 TeV l'énergie de centre de masse en 2012 les mesures sont effectuées en utilisant le J / ψ → ppbar décroissance comme un canal de référence. Haut de centre de masse des énergies disponibles dans les collisions proton-proton au LHC permet modèles décrivant la production de charmonium à tester. Nous distinguons rapidement présenté charmonia de ceux provenant de b-hadron se désintègre. Rapidement produites charmonia comprennent charmonia produit directement dans les interactions parton et ceux provenant de la désintégration de lourdes Etats quarkonium, qui sont à leur tour produit dans les interactions de partons. Production de charmonium invite comprend la production directe de l'interaction de parton et charmonium provenant de désintégrations des etats les plus lourds. Le taux relatif de la production rapide de l'etats η c et J / ψ dans l'acceptation LHCb (gamme de rapidité 2,0 <y <4,5) et pour pT (J/ψ, η c)> 6,5 GeV/c est mesurée pour la première le temps d'être σ (η c) / σ (J / ψ) = 1,74 ± 0,29 ± 0,28 stat syst ± 0,18 B l'énergie de centre de masse 7 TeV, et σ (η c) / σ (J / ψ) = 1,60 ± 0,29 stat ± 0,25 ± 0,17 syst B l'énergie de centre de masse 8 TeV. Utilisation du J / ψ section efficace de production mesurée par LHCb et en supposant qu'aucun J / ψ polarisation, l'absolu η c section efficace de production dans le même régime cinématique est σ η c = 0,52 ± 0,09 ± 0,08 stat syst ± 0,06 σ J / ψ, B l'énergie de centre de masse 7 TeV, et σ η c = 0,59 ± 0,11 stat ± 0,09 ± 0,08 syst σ J / ψ, B l'énergie de centre de masse 8 TeV. La troisième composante d'erreur correspond à l'incertitude de la J / ψ → p et η c → p ramification fractions et la mesure de section eficase J/ψ. Le rapport η c à J/ψ compris fraction de branchement de b-hadron désintégrations est mesuré pour être B (b → η c X) / B (b → J / ψ X) = 0,42 ± 0,06 ± 0,02 stat syst ± 0,05 B. Utilisation de l'J/ψ compris fraction ramification de b-hadron désintégrations mesuré avec le J/ψ →μμ canal de désintégration, l'inclusion η c ramification fraction de b-hadron désintégrations se trouve être B (b → η c X) = (4,9 ± 0,6 ± 0,3 stat syst ± 0,7 B) × 10 ⁻³, où la troisième composante d'erreur correspond à l'incertitude dans les J/ψ → pp et η c → pp ramification fractions (et le J/ψ compris fraction J ramification de b-hadron décroît). La mesure de la fraction η c de branchement inclus rapport de b-hadron se désintègre est la plus précise à ce jour. Utilisation de l'échantillon à faible fond de η c de b-hadron se désintègre, la différence de masse J / ψ et η c, ΔMJ / ψ, η c = 114,7 ± 1,5 ± 0,1 MeV / c², est mesurée. La valeur de la production par rapport compris η c J/ψ est important de faire la distinction entre une grande variété de modèles théoriques. Le η c section est mesurée dans des bacs de dynamique transversale. Il présente un comportement similaire à ceux obtenus dans l'analyse de la production J/ψ, mais avec beaucoup plus importantes incertitudes. Les limites supérieures sur la production de certains autres états charmonium sont adressées. / This thesis addresses a study of the η c (1S) charmonium state using decays to proton-antiproton final state at the LHCb experiment. The production cross-section of the η c meson in parton interactions and in b-hadron decays are reported. Production of the η c (1S) state is measured via the decay to ppbar with the LHCb detector, using an integrated luminosity of 0.7 fb⁻¹ accumulated at 7 TeV centre-of-mass energy in 2011, and an integrated luminosity of 2 fb⁻¹ accumulated at 8 TeV centre-of-mass energy in 2012. The measurements are performed using the J/ψ → ppbar decay as a reference channel. High centre-of-mass energies available in proton-proton collisions at the LHC allow models describing charmonium production to be tested. We distinguish promptly produced charmonia from those originating from b-hadron decays. Promptly produced charmonia include charmonia directly produced in parton interactions and those originating from the decays of heavier quarkonium states, which are in turn produced in parton interactions. Prompt charmonium production comprises direct production in the parton interaction and charmonium originating from decays of heavier states. The relative rate of prompt production of the η c and J/ψ states in the LHCb acceptance (rapidity range 2.0 < y < 4.5) and for p T (J/ψ , η c ) > 6.5 GeV/c is measured for the first time to be σ (η c) /σ (J/ψ) = 1.74 ± 0.29 stat ± 0.28 syst ± 0.18 B at a centre-of-mass energy 7 TeV, and σ (η c) /σ (J/ψ) = 1.60 ± 0.29 stat ± 0.25 syst ± 0.17 B at a centre-of-mass energy s = 8 TeV. Using the J/ψ production cross-section measured by LHCb and assuming no J/ψ polarization, the absolute η c prompt production cross-section in the same kinematic regime is found to be σ η c = 0.52 ± 0.09 stat ± 0.08 syst ± 0.06 σ J/ψ , B at a centre-of-mass energy 7 TeV, and σ η c = 0.59 ± 0.11 stat ± 0.09 syst ± 0.08 σ J/ψ , B at a centre-of-mass energy s = 8 TeV. The third error component corresponds to the uncertainty in the J/ψ → pp and η c → pp branching fractions and the J/ψ cross-section measurement. The relative η c to J/ψ inclusive branching fraction from b-hadron decays is measured to be B(b→η c X) /B(b→J/ψ X) = 0.42 ± 0.06 stat ± 0.02 syst ± 0.05 B. Using the J/ψ inclusive branching fraction from b-hadron decays measured with the J/ψ → μμ decay channel, the inclusive η c branching fraction from b-hadron decays is found to be B(b→η c X) = (4.9 ± 0.6 stat ± 0.3 syst ± 0.7 B) × 10 ⁻³ ,where the third error component corresponds to the uncertainty in the J/ψ → pp and η c → pp branching fractions (and the J/ψ inclusive branching fraction from b-hadron decays). The measurement of the relative η c inclusive branching fraction from b-hadron decays is the most precise to date. Using low-background sample of η c from b-hadron decays, the J/ψ and η c mass difference, ∆M J/ψ , η c = 114.7 ± 1.5 ± 0.1 MeV/c² , is measured. The value of the relative inclusive η c production to J/ψ is important for distinguishing between a variety of theoretical models. The η c cross-section is measured in bins of transverse momentum. It exhibits a similar behaviour to those obtained in the J/ψ production analysis, though with significantly larger uncertainties. The upper limits on the production of some other charmonium states are addressed.

Heavy quarkonium production is not fully understood, but often described by two different models, the Color Singlet Model (CSM), and the Color Octet Model (COM). Previous measurements at the Tevatron collider by the CDF and D0 experiments are not fully in agreement with predicted observables from either model. The Relativistic Heavy Ion Collider (RHIC), and the Solenoidal Tracker At RHIC (STAR) is well suited to further explore heavy quarkonium production. The Heavy Flavor program in STAR encompasses various heavy-flavor analyses, taking advantage of its large solid-angle acceptance, including measurements that explore the properties of heavy quarkonium production using J/ψ and Upsilon (Υ) reconstructions via the di-electron channel, in p+p, d+Au, Cu+Cu, and Au+Au collision systems. This thesis presents results of reconstructed Upsilon (Υ) to study the Upsilon(nS) [n = 1, 2, 3] line- shape and measurements of the production-related observables of spin-alignment (‘polarization’) and Upsilon + hadron correlations (Υ + h) to investigate the Upsilon production mechanism, using triggered data from Run-8 (2008) d+Au and Run-9 (2009) p+p collisions at sqrt(sN N) = 200 GeV, detected at STAR. The result of the spin-alignment measurement is α = 1 ± 0.3 with χ^2 /n.d.f. = 18.71/7 indicating a large (transverse) polarization. The measurement of hadronic activity near the vicinity of an Upsilon, within current uncertainties, is in reasonable agreement with both CSM and COM predictions from PYTHIA, but slightly favors the COM prediction for the near-side Υ + h correlation.

La suppression des Upsilons en collisions d'ions lourdsultrarelativistes est une mesure clé pour la compréhension de l'état dela matière chaude et déconfinée appelé plasma de quarks et de gluons(PQG). Les sections efficaces des états Upsilon Y(nS) sont mesurées encollisions proton-proton et plomb-plomb à une énergie dans le centrede masse de 2.76 TeV par paires de nucléons. Les états individuelssont mesurés via leur canal de désintégration en deux muons, enutilisant le détecteur CMS au CERN. Les sections efficaces mesuréesen pp et PbPb sont comparées grâce au facteur de modification nucléaire, R_{AA}. Cette observable estcalculée pour l'Upsilon(1S) et l'Upsilon(2S) dans plusieursintervalles d'impulsion transverse, de rapidité et de centralité de lacollision. Une limite supérieure sur la production de l'Upsilon(3S)est estimée. Ces mesures montrent une suppression claire etordonnée, en accord avec l'hypothèse de fonte séquentielle desquarkonia dans le PQG. La suppression mesurée pour l'Upsilon(1S) etl'Upsilon(2S) apparaît indépendante de l'impulsion transverse et de larapidité. Des comparaisons avec les modèles phénoménologiquesdisponibles sont présentées, ne reproduisant pas totalement toutes lesobservations. Cette mesure apporte ainsi de nouvelles contraintessur la modélisation du déconfinement des quarks lourds. / Measurements of Upsilon suppression in ultrarelativistic heavy ioncollisions are key to understanding the hot and deconfined phase ofmatter called Quark-Gluon Plasma (QGP). The cross section of Upsilonstates Y(nS) are measured in proton-proton collisions and in lead-leadcollisions at the centre-of-mass energy of 2.76 TeV per nucleonpair. Individual states are measured through their dimuon decaychannel using the Compact Muon Solenoid (CMS) at CERN. The crosssections measured in pp and PbPb are compared thanks to the nuclearmodification factor, R_{AA}. This observable is computed forUpsilon(1S) and Upsilon(2S) in several bins of transverse momentum,rapidity and centrality of the collision. An upper limit on theproduction of Upsilon(3S) in PbPb is estimated. These measurementsexhibit a clear and ordered suppression pattern, consistent with thehypothesis of sequential melting of quarkonia in the QGP. The measuredUpsilon(1S) and Upsilon(2S) suppressions are observed to beindependent of transverse momentum and rapidity. Comparisons withavailable phenomenological models are presented, however fail toreproduce the full set of observations. This novel measurement thusprovides new constraints on the modeling of heavy quark deconfinement.

Neste trabalho obteve-se, com o experimento STAR, medidas de produção de J/&psi; e &upsih; em rapidez central (&eta;=0), em colisões p+p com &radic;s = 200 GeV no RHIC. A medida de &upsih; foi a primeira medida de bottomonium em rapidez central no RHIC. Essas medidas servem como linha de base para a investigação experimental sistemática da supressão de heavy-quarkonium, tida como uma evidência observacional do Plasma de Quarks e Glúons (QGP). Para a realização dessas medidas foi desenvolvido um sistema específico de gatilho de eventos para heavy-quarkonium, envolvendo, em sua configuração, os subsistemas do calorímetro eletromagnético (BEMC) e do cilindro de gatilho central (CTB, apenas para J/&psi;). Os resultados obtidos foram a seção de choque de produção de J/&psi;, BRee&times;&sigma;J/&psi;incl = 122(23)estat(27)sist. (nb), e de &upsih;, BRee&times;d&sigma;&upsih;/dy|y=0 = 114 (29)estat(24)sist. (pb), além do espectro em momento transversal de J/&psi;, cujo momento quadrático médio observado foi &lsaquo; pT2&rsaquo;=3,43(68) (GeV/c)2. Os resultados obtidos foram comparados com previões teóricas de 3 modelos, o de singleto de cor (CSM), QCD não-relativística (NRQCD) e de evaporação de cor (CEM), além de diversos outros dados experimentais. Com excessão do CSM, todos os modelos concordam razoavelmente bem com os dados experimentais. / This work presents mid-rapidity (&eta;=0) J/&psi; and &upsih; measurements for p+p collisions at &radic;s = 200 GeV from the STAR experiment at RHIC. &upsih; results correspond to the first mid-rapidity bottomonium measurement at RHIC. These measurements can be used as the baseline of the systematic experimental investigation on heavy-quarkonium suppression, believed to be one important observational evidence of the existence of the Quark-Gluon Plasma (QGP). In order to acquire the data for these analyses, it was necessary to develop a new heavy-quarkonium trigger system, based on the Barrel Electromagnetic Calorimeter (BEMC) and the Central Trigger Barrel (CTB, J/&psi; only) detectors. The inclusive J/&psi; cross section at mid-rapidity is BRee&times;&sigma;J/&psi;incl = 122(23)estat(27)sist. (nb) and for the &upsih;, BRee&times;d&sigma;&upsih;/dy|y=0 = 114 (29)estat(24)sist.(pb). In the case of the J/&psi; measurement, we acquired enough statistics to obtain a transverse momentum spectrum and the mean squared transverse momentum is &lsaquo; pT2&rsaquo;=3,43(68) (GeV/c)2. These results were compared to theoretical predictions of 3 different models, the Color Singlet Model (CSM), the Non-Relativistic QCD (NRQCD) and the Color Evaporation Model (CEM), as well as to other experimental data. Except for the CSM, all the predictions agree reasonably well with the data.

Un des buts de l'expérience R704 est l'étude des états $\chi_1$ et $\chi_2$ du charmonium $(c\bar{c)}$ dans leur annihilation J/$\psi$ + photon. Ces états sont formés par interaction d'un jet moléculaire d'hydrogène sur un faisceau refroidi d'antiprotons. L'importance du bruit de fond hadronique conduit à ne s'intéresser qu'aux états finaux électromagnétiques. L'appareillage de détection est essentiellement constitué de deux bras symétriques non magnétiques en deux parties. La première s'intéresse seulement aux particules chargées : mesure de leur direction (chambres à fils scintillateurs) et identification des électrons (Cerenkov). La deuxième forme un calorimètre mesurant la position et l'énergie des photons et électrons (sandwiches plomb-scintillateur chambres proportionnelles à lecture cathodique et mur de verre au plomb). L'analyse des données est fondée sur la reconnaissance d'une paire d'électrons provenant d'un $\Psi$, puis la recherche du photon associé, déduit de la reconstruction de la cinématique de la désintégration du $\chi$. Un ensemble de 32 et 55 événements répondent à ses critères ont été isolés, respectivement pour le \chi_1$ et $\chi_2$, avec un bruit de fond négligeable, permettant d'extraire les valeurs de la masse, la largeur et le rapport de branchement $p\bar{p}$. Ces résultats sont comparés aux prévisions théoriques des modèles inspirés de la chromodynamique quantique (QCD) : les masses sont bien décrites par les méthodes de potentiel et de règles de somme (avec une incertitude de l'ordre de 10 MeV). Les prévisions sur les largeurs (calculées à l'ordre 0 de QCD) ne donnent que l'ordre de grandeur de nos résultats alors que celles concernant les rapports de branchement sont en bon accord avec nos mesures.

The correlation function is the critical ingredient for Quantum Chromodynamics (QCD) sum-rule methods that are used to predict hadronic properties. Thus, in order to perform a sum-rule analysis of hybrids, we need to compute a correlation function involving an operator that probes hybrid states composed to quark-antiquark pair with a gluonic excitation. Using particular combinations of quark and gluon fields and Dirac matrices, we construct currents that probe hybrid states with various J^{PC} quantum numbers. We compute the correlation function to order g_s^3 in QCD, obtaining both perturbative and condensate contributions. The focus here is on light quarkonium and strangeonium hybrids, which involve quark masses small compared to the external momentum scale (m_q^2 << Q^2). While for light quarkonium the calculations are performed in the massless limit, for strangeonium we include a strange quark mass correction to the perturbative result. While the details of the calculations outlined throughout this thesis are outlined for J^{PC} = 0^{+-} and 1^{--} due to interest in the exotic quantum numbers 0^{+-}, ultimately the correlation function is computed for all J^{PC} values with J=0,1. Comparison with existing results for a subset of these J^{PC} quantum numbers provides a validation of our calculations.

Neste trabalho obteve-se, com o experimento STAR, medidas de produção de J/&psi; e &upsih; em rapidez central (&eta;=0), em colisões p+p com &radic;s = 200 GeV no RHIC. A medida de &upsih; foi a primeira medida de bottomonium em rapidez central no RHIC. Essas medidas servem como linha de base para a investigação experimental sistemática da supressão de heavy-quarkonium, tida como uma evidência observacional do Plasma de Quarks e Glúons (QGP). Para a realização dessas medidas foi desenvolvido um sistema específico de gatilho de eventos para heavy-quarkonium, envolvendo, em sua configuração, os subsistemas do calorímetro eletromagnético (BEMC) e do cilindro de gatilho central (CTB, apenas para J/&psi;). Os resultados obtidos foram a seção de choque de produção de J/&psi;, BRee&times;&sigma;J/&psi;incl = 122(23)estat(27)sist. (nb), e de &upsih;, BRee&times;d&sigma;&upsih;/dy|y=0 = 114 (29)estat(24)sist. (pb), além do espectro em momento transversal de J/&psi;, cujo momento quadrático médio observado foi &lsaquo; pT2&rsaquo;=3,43(68) (GeV/c)2. Os resultados obtidos foram comparados com previões teóricas de 3 modelos, o de singleto de cor (CSM), QCD não-relativística (NRQCD) e de evaporação de cor (CEM), além de diversos outros dados experimentais. Com excessão do CSM, todos os modelos concordam razoavelmente bem com os dados experimentais. / This work presents mid-rapidity (&eta;=0) J/&psi; and &upsih; measurements for p+p collisions at &radic;s = 200 GeV from the STAR experiment at RHIC. &upsih; results correspond to the first mid-rapidity bottomonium measurement at RHIC. These measurements can be used as the baseline of the systematic experimental investigation on heavy-quarkonium suppression, believed to be one important observational evidence of the existence of the Quark-Gluon Plasma (QGP). In order to acquire the data for these analyses, it was necessary to develop a new heavy-quarkonium trigger system, based on the Barrel Electromagnetic Calorimeter (BEMC) and the Central Trigger Barrel (CTB, J/&psi; only) detectors. The inclusive J/&psi; cross section at mid-rapidity is BRee&times;&sigma;J/&psi;incl = 122(23)estat(27)sist. (nb) and for the &upsih;, BRee&times;d&sigma;&upsih;/dy|y=0 = 114 (29)estat(24)sist.(pb). In the case of the J/&psi; measurement, we acquired enough statistics to obtain a transverse momentum spectrum and the mean squared transverse momentum is &lsaquo; pT2&rsaquo;=3,43(68) (GeV/c)2. These results were compared to theoretical predictions of 3 different models, the Color Singlet Model (CSM), the Non-Relativistic QCD (NRQCD) and the Color Evaporation Model (CEM), as well as to other experimental data. Except for the CSM, all the predictions agree reasonably well with the data.

The large constituent quark mass of bottomonium, the bottom quark/anti-quark bound state $(bbbar)$, affords a rich spectroscopy in which the perturbative (non-relativistic) limit of Quantum Chromodynamics may be theoretically described and experimentally investigated. The radial excitations of bottomonia---with radial quantum number $n$, one unit of total angular momentum $(J=1)$, and orbital angular momentum $L=0$, labeled $Upsilon(nS)$---are copiously produced in electron--positron $(epem)$ collisions. The Belle Collaboration is a high energy physics experiment located at the KEKB B-Factory epem collider, based at KEK in Tsukuba, Japan. Belle has accumulated a large dataset near the FourS and ThreeS resonances, collectively containing more than 28 million ThreeS and 556 million FourS. Some of these decay to other bbbar states---with one unit of orbital angular momentum and total angular momentum $J=0,1,2$, labeled cbj{n} ---via the emission of a photon, with subsequent transition to the OneS with the emission of one or more gluons, which hadronize to form an om meson. This dissertation presents an analysis of the hadronic transitions $chi_{bJ}(nP) rightarrow omega Upsilon(1S)$, where $Upsilon(1S) rightarrow ell^{+}ell^{-}$ with $ell=e,mu$, at Belle. The transitions of the $n=2$ triplet states provide a unique laboratory in which to study nonrelativistic quantum chromodynamics (NRQCD), as the kinematic threshold for production of an $omega$ and $Upsilon(1S)$ lies between the $J=0$ and $J=1$ states. The results presented herein constitute the first confirmation measurement of the $omega$ transitions of the $chi_{bJ}(2P)$ states since their discovery in 2004, with evidence---in excess of three standard deviations---for the sub-threshold transition of the $J=0$ state. The branching fraction $mathcal{B}big( chi_{b0}(2P) rightarrow omega Upsilon(1S) big)$ is found to be as large as the corresponding rate for the $J=2$ transition. The ratio of the $J=2$ to $J=1$ transitions is also measured and compared with the expectation from NRQCD, which we compute, revealing a $3.3sigma$ tension between experiment and theory. This work is leveraged to perform a search for radiative transitions of the $Upsilon(4S)$ to the $chi_{bJ}(2P)$ and $chi_{bJ}(3P)$ states, which are reconstructed in an inclusive $omega Upsilon(1S)$ final state. With no significant signal seen, limits are set on the corresponding branching fractions. / Doctor of Philosophy / Atoms, the stuff of everyday matter, consist of a number of electrons bound to a compact nucleus. This nucleus, in turn, contains one or more protons and neutrons, which are themselves made up of constituent particles called quarks that interact with one another by exchanging particles called gluons. Although great strides were made during the last century to further our understanding of the fundamental structure of matter, a comprehensive description of nuclear structure, at the quark level, eludes us. What we do know is that the force responsible for binding the large number of positively charged protons within the narrowly confined nucleus of, say, a gold atom is incredibly strong---in reality, more than 137 times as strong as the electromagnetic (EM) interaction, which is responsible for binding electrons around the nucleus in atoms. Unlike the EM force, which has one charge that can be either positive or negative, the strong interaction has three. This leads to a manifestly more complicated phenomena whose mathematical descriptions are computationally intractable. To study the strong interaction, we seek out the simplest of strongly bound states---called the meson---which consist of a quark and its anti-particle counterpart. The meson made up of a bottom quark/anti-quark pair, called bottomonium, provides an ideal laboratory for our investigations. In bottomonium, the quarks are very heavy (about 4.5 times the mass of a proton) and move relatively slowly compared to the quarks within a proton. This allows for some simplifications in the mathematical description of the bottomonium system, making it possible to compute predictions that can be tested in the lab. In this low energy regime, the strong interaction gives rise to a family of excited bottomonium states that have a structure similar to the excited states of an atom. Just as scientists learned about the EM interaction by studying the decays of excited atomic states, so too do we study the strong force by measuring the decays of bottomonium states. We call this study heavy quarkonium spectroscopy. When excited bottomonium states transition to lower-energy states, they may emit photons (as excited atoms do) or gluons. These emitted gluons, in turn, produce other particles. Measurements of the decay rates of bottomonium states may be predicted from the mathematical description of the strong interaction, providing direct experimental tests of the theoretical models. This dissertation presents a study of the decays of several bottomonium states, which are produced at the Belle experiment at the KEKB electron--positron collider. The decay rates, called the branching fractions, of these transitions are measured and used to test the prediction from theory, which we calculate. This work is leveraged to search for several previously unobserved decays, which are expected to be exceptionally rare.

La matière nucléaire, constituant le noyau des atomes, est formée de quarks et de gluons, dont l’interaction est décrite par la théorie de la chromodynamique quantique (QCD). Dans des conditions normales, quarks et gluons ne peuvent être observés de façon isolée et sont confinés dans des hadrons tels que les protons et les neutrons. Le Plasma de Quarks et de Gluons (PQG) est un état de la matière nucléaire prédit par la QCD pour lequel ces quarks et gluons sont déconfinés. Expérimentalement, le PQG peut être créé dans des collisions d’ions lourds ultra-relativistes, telles que les collisions d’ions lourds effectuées au LHC, correspondant à des vitesses proche de celle de la lumière. Il est possible d’obtenir des informations sur le PQG en mesurant un large nombre d’observables. En particulier, la production de charmonium tels que le J/ψ et le ψ(2S), particules lourdes constituées d’une paire de quarks charme et anti-charme () est mesurée pour étudier le plasma. En effet, la présence d’un PQG est censée modifier les taux de production des charmonia, à cause d’un équilibre entre un mécanisme d’écrantage de couleur du potentiel des quarks charme et un mécanisme dit de recombinaison. La position de cet équilibre dépend de l’énergie de collision, la température du plasma, et la nature de la particule considérée, et plus spécifiquement, il est attendu que le ψ(2S) soit plus supprimé que le J/ψ. Dans cette thèse, la production inclusive de ψ(2S) en collisions Pb − Pb à une énergie par collision nucléon-nucléon dans le référentiel du centre de masse de TeV est mesurée dans le canal de décroissance de dimuon avec le Spectromètre à Muons d’ALICE. L’analyse est basée sur les données collectées dans ALICE (A Large Ion Coliider Experiment) au LHC en 2015 correspondant à une luminosité intégrée de 225 μb−1. Le facteur de modification nucléaire RAA est étudié en fonction de la centralité des collisions, correspondant à la distance transverse entre les centre des noyaux de plomb. Le rapport des RAA du ψ(2S) et du J/ψ est également mesuré et montre que le ψ(2S) est plus supprimé que le J/ψ pour des collisions mi-centrales et centrales. Comparées aux prédictions théoriques, les mesures sont compatibles avec les modèles dans la limite des incertitudes. L’amélioration du Muon Trigger, le MID, est également étudié, en particulier le débit de données attendu pour des fréquences de collision de 100 kHz. Basée sur les données en collisions Pb − Pb à une énergie de TeV, les estimations prédisent que la technologie qui sera implémentée sur le MID possède une bande passante suffisante. / The nuclear matter, which constitues the atomic nuclei, is composed of quarks and gluons and interactions between them are described by quantum chromo-dynamics (QCD). Under ordinary conditions, quarks and gluons cannot be observed isolated and are confined inside hadrons such as protons and neutrons. The Quark-Gluon Plasma (QGP) is a state of nuclear matter predicted by QCD where quarks and gluons are deconfined. Experimentally, a QGP can be created in ultra-relativistic heavy ion collisions such as the lead-lead collisions delivered at the LHC, corresponding to speeds close to the speed of light. It is possible to obtain information on the characteris- tics of the QGP by measuring a large number of observables. In particular, the production of charmonium states such as the J/ψ and the ψ(2S), heavy particles composed of a charm and anti-charm pair (), is studied to investigate the plasma. Indeed, the presence of QGP is expected to modify the charmonium production yields, due to a balance between the mechanism of color screening of the charm quark potential and a mechanism called recombination. This balance depends on the collision energy, the temperature of the plasma and nature on the considered particle, in particular one expects the ψ(2S) to be more suppressed than the J/ψ. In this thesis the inclusive production of ψ(2S) in Pb − Pb collisions at an energy per nucleon-nucleon collision in the center of mass frame of TeV is measured in the dimuon-decay channel, using the ALICE Muon Spectrometer. The analysis is based on the data collected in ALICE (A Large Ion Collider Experiment) at the LHC in 2015 with an integrated luminosity of 225 μb−1. The nuclear modification factor RAA is studied as a function of centrality. The ratio of the ψ(2S) and J/ψ RAA is also evaluated and shows that the ψ(2S) is more suppressed than the J/ψ for mid-central and central events. Compared with theoretical predictions, the measurements are, within uncertainty, in agreement with theoretical model. The upgrade of the Muon Trigger, the MID (Muon Identifier), is also studied, in particular the expected data flow at a collisions rate of 100 kHz. Based on the Pb − Pb data at a collision energy of TeV, the estimations predict that the technology that will be implemented in the MID provides a sufficient bandwidth to sustain the data flow.

La théorie de la chromodynamique quantique prédit l’existence d’un état déconfiné de la matière appelé Plasma de Quarks et de Gluons (PQG). Expérimentalement, la formation d’un PQG est attendue sous les conditions extrêmes de température et de densité atteintes lors de collisions d’ions lourds ultra-relativistes. Afin d’observer et de caractériser de manière indirecte un tel état de la matière, de nombreuses observables ont été proposées. En particulier, les phénomènes de suppression et de(re)combinaison du meson J/Ψ dans le PQG sont intensément étudiés. Cette thèse présente l’analyse de la production inclusive de J/Ψ dans les collisions Pb-Pb, à une énergie dans le centre de masse √sNN = 2,76 TeV, détectés avec le spectromètre à muons de l’expérience ALICE au LHC. A partir de la statistique élevée d’événements collectés lors de la prise de données de 2011, le facteur de modification nucléaire du J/Ψ a été mesuré en fonction de son impulsion transverse, de sa rapidité et de la centralité de la collision. L’impulsion transverse moyenne du J/Ψ a également été mesurée en fonction de la centralité. Les prédictions des modèles théoriques, incluant tous une contribution de (re)combinaison, présentent un bon accord avec les données. Enfin, un excès de J/Ψ de très faible impulsion transverse (<300 MeV/c) par rapport à la production hadronique attendue a été observé pour la première fois. / The quantum chromodynamics theory predicts the existence of a deconfined state of matter called Quark Gluon Plasma (QGP). Experimentally, the formation of a QGP is expected under the extreme conditions of temperature and density reached in ultra-relativisticheavy-ion collisions. Many observables were proposed to observe and characterize indirectly such a state of matter. In particular, the phenomena of suppression and (re)combination of the J/Ψ meson in the QGP are extensively studied. This thesis presents the analysis of the inclusive production of J/Ψ in Pb-Pb collisions, at a center of mass energy √sNN = 2.76 TeV, detected with the ALICE muon spectrometer at the LHC. From the high statistics of events collected during 2011 datataking, the J/Ψ nuclear modification factor was measured as a function of transverse momentum, rapidity and collision centrality. The J/Ψ mean transverse momentum was also measured as a function of centrality. The predictions of theoretical models, all including a (re)combination contribution, are in good agreement with data. Finally, an excess of J/Ψ yield at very low transverse momentum (<300 MeV/c) with respect to the expected hadronic production was observed fort he first time.