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1
Berrehrah, Hamza. "Propagation et collectivité des quarkonia dans le plasma de quarks et de gluons : vers la suppression de la suppression du J/ψ à hautes températures." Nantes, 2011. http://www.theses.fr/2011NANT2115.
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Depuis 25 ans, la suppression des quarkonia a été étudiée comme sonde du plasma de quarks et de gluons (PQG). Néanmoins, la comparaison entre les données expérimentales et les scénarios incluant cette suppression n'est pas concluante. Une voie alternative est d'étudier non seulement la suppression mais aussi les propriétés physiques des quarkonia survivants dans le PQG. En effet, des résultats récents du SPS montrent un flot elliptique de quarkonia non nul. De plus, des résultats du RHIC suggèrent une forte thermalisation des quarks charmés dans le milieu. Il en résulte un faible coefficient de diffusion et une séparation finale modérée entre les constituants du J/ψ qui limiterait sa suppression (suppression de la suppression). Ce phénomène motive l'intérêt de l'étude dynamique des quarkonia. Cette thèse propose d'étudier les aspects physiques sous-jacents à la propagation et à la collectivité des quarkonia dans le PQG. Cette étude est basée sur un code hydrodynamique de transport décrivant l'évolution stochastique d'un état lié dans un fluide chaud. Les ingrédients nécessaires à ce modèle sont, entres autres, l'évaluation des processus de diffusion élastique et inélastique quarkonia-gluon/quark/hadron et l'estimation des pertes d'énergie collisionnelles et des forces stochastiques du bain thermique. Pour mener à bien cette étude, nous avons développé un cadre théorique combinant des calculs analytiques en pQCD, des considérations phénoménologiques et des résultats de lQCD. Le rôle du processus de diffusion élastique lors de la propagation des quarkonia dans le PQG a été mis en évidence dans notre étude. De plus, des éléments caractérisant la collectivité des quarkonia sont apportésThe suppression of quarkonia has been studied as a probe of the quark gluon plasma (QGP) properties for 25 years. However, the comparison between experimental data and theoretical scenarios including suppression mechanisms is not very conclusive. An alternative track is to study not only the suppression but also the physical properties of quarkonia survivors in the QGP. In fact, recent SPS results showed a non-zero quarkonia elliptic flow. On the other hand, recent RHIC results suggest a strong thermalization of charm quarks in the medium. Therefore, it follows a small diffusion coefficient and a moderate final separation between the two constituents of the bound state. This would limit the J/ψ suppression (suppression of the J/ψ suppression) and motivate the interest to study the quarkonia dynamics in the QGP. This thesis focuses on the study of the physical aspects underlying the quarkonia propagation and collectivity in the QGP. The study is performed using a hydrodynamic transport model describing the stochastic evolution of a bound state in a hot fluid. The ingredients for this approach are, among others, the evaluation of the elastic and inelastic quarkonium-gluon/quark/hadron scattering processes, and a relevant estimation of the collisional energy losses and stochastic forces of the thermal bath. To conduct this study, we developed a theoretical framework by combining analytical calculations based on pQCD, phenomenological considerations and results from lQCD. The role of elastic scattering process during the quarkonia propagation in the QGP has been demonstrated in our study. In addition, elements that characterize the quarkonia collectivity in the medium were obtained
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Muramatsu, Hajime Skwarnicki Tomasz. "Photon spectroscopy of heavy quarkonia." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2004. http://wwwlib.umi.com/cr/syr/main.
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BASTOS, Cristiano Costa. "Química com quarks." Universidade Federal de Pernambuco, 2007. https://repositorio.ufpe.br/handle/123456789/8777.
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Previous issue date: 2007Algumas propriedades da química de quarks podem ser obtidas realizando cálculos ab initio Hartree-Fock para átomos com carga nuclear fracionária e moléculas formadas por estes átomos. Obtivemos o estado fundamental e o primeiro estado excitado para os átomos de sódio, lítio, berílio e magnésio interagentes com quarks. Isto sugere que transições eletrônicas podem ser usadas como guia para detecção de quarks livres. Analisamos a variação da energia de ligação eletrônica com a carga nuclear para as séries isoeletrônicas de átomos com carga nuclear fracionária A±2/3 e A±1/3 (A = H, Li, Na, P and Ca). Isto mostra que partículas de cor não confinadas preferem se ligar a átomos pesados e o par quark-antiquark pode ser estabilizado na presença da matéria atômica
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Rakotozafindrabe, Andry. "Etude de l'effet d'écrantage de couleur dans un plasma de quarks et de gluons sur les taux de production des quarkonia dans les collisions d'ions lourds auprès de l'expérience PHENIX." Phd thesis, Ecole Polytechnique X, 2007. http://pastel.archives-ouvertes.fr/pastel-00003165.
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Les collisions d'ions lourds relativistes permettent d'étudier la production du plasma de quarks et de gluons (QGP), état dans lequel serait la matière hadronique au-delà d'une température de l'ordre de 200~MeV. Le $J/\psi$, état lié~$c\bar{c}$, est une des sondes utilisées pour observer le QGP. Son taux de production peut être modifié par divers effets en compétition: les effets nucléaires froids et ceux attendus en cas de production du QGP. Une suppression anormale du $J/\psi$ (au-delà des effets froids) a déjà été vue par l'expérience NA50 (SPS) dans les collisions Pb~+~Pb les plus centrales. L'expérience PHENIX (RHIC) poursuit cette étude à une énergie environ dix fois plus élevée. Nous avons étudié la production du $J/\psi\to\mu^+\mu^-$ dans les collisions Cu~+~Cu effectuées en 2005 à une énergie de 200~GeV par paire de nucléons. Les résultats obtenus apportent des informations importantes sur les effets froids: ils permettent d'améliorer de manière significative la précision obtenue dans les collisions à petit nombre de nucléons participants, où le QGP ne peut être produit. Ils confirment la similitude des suppressions déjà observées au RHIC dans les collisions Au~+~Au et au SPS; ce constat restant à corroborer par des mesures plus précises des effets froids au RHIC. Les résultats combinés Au~+~Au et Cu~+~Cu mettent aujourd'hui en défaut la plupart des modèles théoriques, et pourraient favoriser l'hypothèse d'une production ! secondaire du $J/\psi$ dans le milieu (recombinaison).
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Devlin, Francis Robert. "Physics of heavy quarks." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319786.
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Veiga, J. S. "Propriedades da matéria nuclear em modelos de quarks constituintes /." São Paulo, 1996. http://hdl.handle.net/11449/132865.
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Koempel, John Paul. "Exclusive Production of Quarkonia and Generalized Parton Distributions." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/319337.
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PhysicsPh.D.
The understanding of the nucleon is as of yet not complete. In particular, the contribution of the gluon content is not well understood. Utilizing the framework of Generalized Parton Distributions enables predictions to be made if some information on them is known. We investigated exclusive photo and electroproduction of heavy vector mesons (the quarkonia J/ψ and ϒ), which can give access to the currently poorly constrained gluon distribution Eg. For this reason, we implemented a model for it with several variants in order to represent a spread of plausible distributions. We used current experimental results for exclusive φ and ρ0 production to test our variants for Eg. For quarkonium production, the analytic calculation of the Leading Order production amplitudes was performed, verifying results published previously, in particular confirming that in the non-relativistic collinear approximation there is no access to the polarized or gluon helicity flip distributions, i.e. Hg and HgT. Numerical results for both the Leading Order and, in the case of photoproduction, also Next-to-Leading Order amplitudes were calculated, based on our Leading Order amplitudes and already existing Next-to-Leading Order expressions. The observables we looked at are the unpolarized cross section, spin density matrix elements, and two spin-asymmetries --- the transverse single-spin asymmetry An, and a newly discussed double-spin asymmetry ALS, which we identified as a very promising observable for measuring Eg. We find that in the case of J/ψ photoproduction higher order corrections seem not well under control, while for ϒ production the numerical results become much more stable.
Temple University--Theses
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Smith, Jason. "Quarks and antiquarks in nuclei /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9750.
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Leyva, Alfonso. "Strahlungskorrekturen zu Polarisationsobservablen schwerer Quarks." [S.l. : s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2000/0128/diss.pdf.
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Higuchi, Katsuichi. "Electroweak Interaction with Singlet Quarks." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/152527.
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Ünalan, Zeynep. "A measurement of the top quark's charge." Diss., Connect to online resource - MSU authorized users, 2008.
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Guerin, F. "Sonde muonique et instrumentation associée pour l'étude du plasma de quarks et de gluons dans l'expérience ALICE." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2006. http://tel.archives-ouvertes.fr/tel-00132781.
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ALICE est le détecteur du LHC dédié à l'étude des collisions d'ions lourds ultra-relativistes. Le principal objectif de cette expérience est la mise en évidence et l'étude d'une nouvelle phase de la matière nucléaire prédite par la théorie de la chromodynamique quantique (QCD) : le Plasma de Quarks et de Gluons (PQG). Une des signatures possibles est la suppression des taux de production des quarkonia par écrantage de couleur dans les collisions d'ions lourds, dans lesquelles la formation d'un plasma est attendue. Le spectromètre à muons permettra de mesurer les taux de production des quarkonia (J/Psi, Upsilon) dans les collisions d'ions lourds via leur canal de désintégration dimuonique. Un système de déclenchement rapide, associé au spectromètre à muons, est chargé de sélectionner les événements contenant au minimum un muon ou un dimuon à l'aide d'un algorithme de recherche de traces. L'étude des performances du système de déclenchement du spectromètre à muons, réalisée à l'aide de simulations Monte-Carlo, sera présentée dans ce mémoire en mettant l'accent sur l'efficacité et la fréquence de déclenchement du système dans le cas des collisions Pb-Pb et Ar-Ar. Nous présenterons également la reconstruction du spectre en masse des dimuons de signes opposé avec le spectromètre à muons d'ALICE. A partir de ce spectre, les taux de production des états Upsilon seront extraits pour un mois de collisions Pb-Pb au LHC et pour diverses tranches en centralité.
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Moreno, Torres Daniel. "Non-relativistic bound states in QCD: towards the N3LL heavy quarkonium spectrum." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667376.
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Mauser, Marcus. "Polarisationseffekte in semileptonischen Zerfällen schwerer Quarks." [S.l. : s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0051/diss.pdf.
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Jain, Ambar. "Heavy quarks in effective field theories." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53228.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 279-290).
Heavy quark physics serves as a probe to understand QCD, measure standard model parameters, and look for signs of new physics. We study several aspects of heavy quark systems in an effective field theory framework, including both phenomenological and formal applications. Phenomenological applications include the leading calculation of penguin amplitudes in charmless non-leptonic B-decays to light mesons, including power suppressed effects that are numerically enhanced by the chiral condensate. We compare our determination of the penguin amplitudes with the experimental results. Also, we calculate the heavy quark jet function at two loops, which is an important ingredient for the next-to-next-to-leading-log invariant-mass distribution of jets induced by tt pair production at a future linear collider. Formal applications include: a definition of top mass relevant for measurements that use top induced jets, a new renormalization group equation in an infrared scale intrinsic to heavy quark masses and its generalization for QCD matrix elements, a threshold mass definition which smoothly connects to the MS mass, and a new method to analyze renormalons in the operator product expansion.
by Ambar Jain.
Ph.D.
16
Enström, Daniel. "Aspects of quarks in exotic matter." Licentiate thesis, Luleå tekniska universitet, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16915.
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In this licentiate thesis, two different aspects of particle physics have been studied. The results are presented in four papers. In papers I and II, a model for a joint origin of gamma-ray bursts and dark matter is presented. The common denominator is the deconfined state of quarks, the Quark-Gluon Plasma (QGP). We propose that such quark objects surviving the quark-hadron transition in the early universe, constitute the dark matter and that mergers of these objects are the inner engine of gamma-ray bursts. We have computed stability criteria for macroscopic quark objects, as well as the merger frequency assuming a lognormal distribution in size. In paper III, the helicity amplitudes for rare-meson production invirtual gamma-gamma collisions are computed. We show that it is possible to apply a generalised version of the Brodsky-Lepage scheme for exclusive processes in QCD, when computing these amplitudes. In paper IV, we analyse consequences of the new supernova data, suggesting a non-zero vacuum energy density in the universe. We calculate the intrinsic luminosity correction for high-redshift objects such as gamma-ray bursts and quasars. Two different extensions of the Friedmann-Robertson-Walker universe are used; a non-zero cosmological constant and a time-dependent spatially inhomogeneous energy density component (so-called quintessence). The results show a correction of up to 30% for the conventionally computed luminosities.Godkänd; 1999; 20070321 (ysko)
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Geng, Chaqiang. "Composite models of quarks and leptons." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/76097.
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We review the various constraints on composite models of quarks and leptons. Some dynamical mechanisms for chiral symmetry breaking in chiral preon models are discussed. We have constructed several "realistic candidate" chiral preon models satisfying complementarity between the Higgs and confining phases. The models predict three to four generations of ordinary quarks and leptons.Ph. D.
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Boyd, Graham John. "Quarks and hadrons on the lattice." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/15902.
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Bibliography: p. 159-166.There is a short introduction to the ideas of lattice theory, followed by an equally brief look at pure gauge QCD on the lattice. More details for either of these may be found in the references cited in each section, as well as in [143]. The bulk of this work deals with the problems encountered in placing fermions on to the lattice, and the techniques used for this purpose. The Nielsen-Ninomiya theorem is introduced, with a detailed treatment thereof relegated to an appendix. The two main fermion techniques, due to Wilson (1974); and Kogut and Susskind (1975) are dealt with in some detail. This is followed by a discussion of the construction of hadrons on the lattice, using either Wilson or Kogut-Susskind fermions. There is a chapter covering the algorithms used in numerical simulations of lattice QCD, with some examples illustrating them. The thesis concludes with a discussion of the results obtained thus far on the hadron spectrum, in both the quenched approximation as well as those obtained using dynamical quarks.
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Agudelo, David Felipe Tamayo. "Materia de quarks a temperatura finita." reponame:Repositório Institucional da UFSC, 2013. https://repositorio.ufsc.br/handle/123456789/106802.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2013Made available in DSpace on 2013-12-05T22:23:58Z (GMT). No. of bitstreams: 1 318335.pdf: 3639601 bytes, checksum: 3015447719eab188881d3532f1267586 (MD5) Previous issue date: 2013
A constitução dos objetos estelares continua sendo fonte de especulação. Varias hipótesis têm sido aventadas com relação a estrutura interna dos pulsares. Uma delas basei-se na conjetura de Bodmer-Witten, de que a altas densidades a matéria mias estável é formada por quarks desconfinados. Nesse caso, os pulsares seriam estrelas quarkiônicas, constituídas somente de quarks e léptons.O modelos mais comumente usado para descrever matéria de quarks é o modelo de sacola de MIT. Outro modelo, um pouco mais sofisticado é modelo dependente da densidade ou Quark mass density dependent model. Neste trabalho pretendemos comparar as equações de estado desses dois modelos, tanto a temperatura zero, como a temperatura finita. Essas equações de estado servem de input para as equações de Tlman-Oppenheimer-Volkoff (TOV), que são equações da relatividade geral para objetos homogéneos e de simetría esférica. Os resultados obtidos são os valores para massas e raios das estrelas.
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Rosnet, P. "Les saveurs lourdes dans les collisions d'ions lourds ultra-relativistes." Habilitation à diriger des recherches, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00262436.
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Les collisions d'ions lourds ultra-relativistes représentent le seul moyen pour appréhender en laboratoire le diagramme de phase de la QCD, la théorie de l'interaction forte. Les prédictions théoriques les plus récentes, obtenues par la technique de calcul sur réseau, prévoient une transition de phase entre la matière nucléaire froide (un gaz hadronique) et un plasma de quarks et de gluons (milieu déconfiné). Parmi les différentes sondes expérimentales possibles, l'intérêt des saveurs lourdes est en principe de pouvoir caractériser le milieu produit lors d'une collision entre ions lourds, mais également de pouvoir obtenir des informations sur son évolution spatio-temporelle. Leur étude peut se faire entre autres par le biais de leur canal de désintégration en muons. Cette Habilitation à Diriger des s développe dans une première partie la problématique des collisions d'ions lourds ultra-relativistes, en mettant l'accent sur l'étude des saveurs lourdes. Dans une deuxième partie, les résultats obtenus auprès du collisionneur RHIC (BNL, New York) sont passés en revus, et l'analyse du spectre en masse des dimuons menée au sein de l'expérience PHENIX est détaillée. Enfin, la troisième partie décrit d'une part les développements instrumentaux réalisés pour le système de déclenchement des muons dans l'expérience ALICE auprès du LHC (CERN, Genève), et d'autre part les performances attendues pour l'étude des dimuons.
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Hadjimichef, Dimiter. "Formalismo de Fock-Tani para a física hadrônica /." São Paulo, 1995. http://hdl.handle.net/11449/132802.
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Orientador: Gastão Inácio KreinBanca: Mahir Saleh Hussein
Banca: Yogiro Hama
Banca: Eliane Angela Veit
Banca: Rogério Rosenfeld
Resumo: O formalismo de teoria de campos Fock-Tani, o qual foi originalmente desenvolvido na física atômica para tratar sistemas em que os graus de liberdade internos dos átomos não podem ser desprezados, é generalizado para sistemas de hádrons compostos. Partindo da representação no espaço de Fock dos estados hadrônicos num modelo de quarks, uma mudança de representação é implementada de tal maneira que os hádrons sejam descritos por operadores de campo de partículas elementares. A aplicação da transformação unitária ao Hamiltoniano microscópico de quarks dá origem a Hamiltonianos efetivos que descrevem interações quark-quark, hádron-hádron, e hádron-quark. Hamiltonianos bariônicos efetivos foram derivados no contexto de um modelo de quarks constituintes. Em particular, um potencial efetivo NN foi obtido, deslocamentos de fase singletos de spin foram calculados para este potencial e comparados aos deslocamentos de fase gerados pela troca de mésons 'ômega' do potencial de Bonn
Abstract: The field theoretic Fock-Tani formalism, originally developed in atomic physics to deal with systems where the internal degrees of freedom of atoms cannot be neglected, is generalized to composite hadronic systems. Starting from the Fock space representation of hadron bound states in a quark model, a change of representation is implemented by a unitary transformation such that the composite hadrons are redescribed by elementary-particle field operators. Application of the unitary transformation to the microscopic quark Hamiltonian gives rise to effective Hamiltonians that describe quark-quark, hadron-hadron, and quark-quark interactions. Effective baryon Hamiltonians are derived in the context of a constituent quark model. In particular, an efective NN Fock-Tani potential was obtained, spin-singlet phase shifts were calculated for this potential and compared with the ones generated by the 'ômega' exchange of the Bonn potential
Doutor
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Katz, Roland. "A quantum approach to dynamical quarkonia suppression in high energy heavy ion collisions." Thesis, Nantes, Ecole des Mines, 2015. http://www.theses.fr/2015EMNA0227/document.
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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 théoriquesThe 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
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Takan, Taylan. "Study Of The Heavy Quarkonia Spectra In The Quark Model." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614102/index.pdf.
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Conventional Heavy Quarkonium systems, Charmonium and Bottomonium, are believed to
be composed of a heavy quark and anti-quark pair. These systems are investigated by dierent
methods resulting from dierent approaches to Quantum Chromodynamics (QCD), such as
Lattice QCD, Eective Theories and Sum Rules. In this thesis we study the spectrum of
Charmonium and Bottomonium using a non-relativistic Quark Model. Assuming one gluon
exchange for the short distances and a linear confining potential for long distances we derive
Breit-Fermi interaction Hamiltonian and calculate the spectra arising from this Hamiltonian.
Also we calculate the partial widths of E1 and M1 radiative decays.
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Isert, Dagmar Sigrun. "Transport theory for scalar quarks and gluons." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961877200.
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Webster, Stephen James. "Improved Monte Carlo simulations of massive quarks." Thesis, Durham University, 2019. http://etheses.dur.ac.uk/12954/.
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Motivated by the interest in top and bottom quark production processes at the LHC, we study the simulation of heavy quarks in the Herwig 7 Monte Carlo event generator. We first present a much improved treatment of heavy quarks in the dipole shower in Herwig 7 and extend the shower to handle decays of massive coloured particles. Taking advantage of these developments, we perform an in-depth study of the simulation of top quark pair production at the LHC, paying particular attention to the parton shower and matching uncertainties involved. Next we implement an algorithm in the dipole shower to include spin correlation effects. Using this algorithm we can produce accurate predictions of the angular distributions of top quark decay products in top pair production at the LHC. Following this we describe a modified version of the veto algorithm used in parton showers that enables the incorporation of weights. We show that the algorithm can be used to significantly reduce the CPU time required to evaluate the effects of scale variations in parton showers. Finally, we investigate the description of gluon splittings to heavy quark pairs in the angular-ordered and dipole parton showers in Herwig 7. While both parton showers correctly reproduce the leading-logarithmic term in the description of these splittings, we find that the effects of subleading contributions are significant.
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Martins, Mauro Sebastião. "História das partículas: de elétrons aos quarks." Pontifícia Universidade Católica de São Paulo, 2008. https://tede2.pucsp.br/handle/handle/13384.
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Previous issue date: 2008-05-13This Work, a thesis in history of subatomic particles, is an historic and epistemological development study of the theoretical and experimental subatomic particles and antiparticles from the early Dirac s quantum theory of the electron, published in a year of 1928, until the publications of the theories of the quarks in a decade of the sixths, the Gell Mann theory of quarks include. That research studies was made in primaries and secondary bibliographies, didactic manuals, articles of scientific journals and scientific magazines, history and philosophy of science books and history of particles books. This studies show that in the delimitated period of study, the paradigmatic theories and experiments appear in the period call of common science, in suite the scientific period is the crisis, so, have a concurrency theories and experimental models period, finally appear a paradigmatic theory and experimental model, like the Khun historical analyses. The paradigmatic particles theories and experimental models, appear a manner of broke up whit of old scientific know, like understood of Bachelard analysis. In the daily period the candidate of paradigmatic theory of particles is the supercordas theory. However, ours studies are conclusive that it have a periodic cycle, into theirs, appear the paradigmatic theoretical and experimental models and had surpassed in the suite period by others paradigmatic theoretical and experimental models, and other periodic cycle occur when of paradigmatic theories and experimental models appear, and so on
Este trabalho, uma tese em história das partículas subatômicas, é um estudo da evolução histórica e epistemológica das teorias e experimentos em partículas e antipartículas, desde o advento da teoria quântica do elétron de Dirac, no ano de 1928, até as publicações das teorias sobre os quarks da década de sessenta, incluindo, nestas, a teoria dos quarks de Gell Mann. Os estudos foram embasados nos levantamentos de bibliografias primárias e secundárias: manuais didáticos, artigos de revistas e jornais científicos, obras em história e filosofia da ciência e em história das partículas. Ele demonstra que o período delimitado para o estudo revela que as teorias e experimentos paradigmáticos surgem após um período de ciência normal, seguido de crise e concorrência entre as teorias e modelos experimentais, como compreendido pela análise histórica de Thomas Khun. As teorias e experimentos paradigmáticos, em partículas, surgem de rupturas com o velho conhecimento estabelecido, como entendido pela análise epistemológica de Bachelard, do desenvolvimento do conhecimento científico. No período atual a candidata à teoria paradigmática em partículas, segundo a manifestação da comunidade científica dos pesquisadores em física de partículas, é a teoria das supercordas. Entretanto, os estudos são conclusivos, quanto à existência de ciclos periódicos, nos quais, as teorias e modelos paradigmáticos aparecem e são superados por outras teorias e modelos paradigmáticos emergentes
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Prager, Hugo. "Phenomenology of extra quarks at the LHC." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/424495/.
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In this thesis, we study in a model independent way models of new Physics featuring extra quarks (XQs). These quarks are predicted by several extensions of the Standard Model (SM) but have never been observed yet even though many searches have been designed to find them at the Large Hadron Collider (LHC). After an introduction about the SM and the LHC, we present the main properties of these XQs and a model independent parametrisation that can be used to describe their phenomenology with generic hypotheses about their mixing with SM quarks, both in the case of XQ coupling with SM bosons and with Dark Matter (DM) candidates. In these two cases we study the offshellness effects in pair-production and decay and show that if the Narrow-Width Approximation (NWA), that we describe in detail, is a good approximation of the full result in the small width over mass ratio limit, sizeable differences occur when the XQ width becomes larger. The conclusion of our analysis is that even though the small width assumption is always conservative it is not possible to trivially rescale the mass bounds obtained considering processes of pair production and decay in the NWA to determine constraints for XQs with large widths. We also study the role of interference in the process of pair production of new heavy XQs decaying to SM particles and show that in the NWA the interference contribution can be described by considering a parameter which contains only the relevant couplings and the scalar part of the propagators of the new quarks, both at the cross section level and at the distribution level. Finally, we study how various Supersymmetry (SUSY) searches perform for our simplified model with XQs decaying to DM. We show that cross section upper limit maps and efficiency maps obtained for stop simplified models in stop searches can also be applied to analogous XQ models, provided the NWA applies: the bound for XQs can therefore be obtained from the SUSY ones just by rescaling the exclusion with the XQ cross section.
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GIRLANDA, LUCA. "Signature experimentale de la condensation de quarks." Paris 11, 1999. http://www.theses.fr/1999PA112258.
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Cette these est dediee a l'etude du mecanisme de la brisure spontanee de la symetrie chirale en qcd. En particulier on a voulu mettre en evidence le role du parametre d'ordre le plus simple, le condensat de quarks <$$q>. Apres avoir decrit differents scenarios possibles de la structure en phases du vide de la qcd, comme fonction du nombre de saveurs de masse nulle n f et de couleurs n c, nous nous sommes concentres sur le cas n f = 2. Afin d'inspecter systematiquement la sensibilite des processus physiques a la valeur du condensat <$$att$$q>, nous avons construit et renormalise, a l'ordre d'une boucle, la version generalisee de la theorie des perturbations chirale, dans le cas de symetrie su(2)su(2). Les applications phenomenologiques etudiees incluent la diffusion a basse energie, les desintegrations 3 + $$att$$ et les desintegrations inclusives non-etranges du lepton. Nous avons illustre comment determiner <$$att$$q> a partir de donnees de haute precision qui sont attendues, dans le domaine de la diffusion , par les experience e865 a bnl, kloe a dane et dirac au cern, et dans le domaine des desintegrations du lepton par les nouvelles usine a b de haute luminosite (babar, cleoiii-cesr).
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Al, Mamun Md Abdullah. "Nuclei, Nucleons and Quarks in Astrophysical Phenomena." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1563991151449461.
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Lasry, Nathaniel. "Mélange des quarks : une nouvelle approche géométrique /." Thèse, Montréal : Trois-Rivières : Université du Québec à Montréal, Université du Québec à Trois-Rivières, 2000. http://www.uqtr.ca/biblio/notice/resume/03-2224587R.html.
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Mémoire (M.Sc.)--Université du Québec à Montréal, 2000.En tête du titre: Université du Québec à Montréal. "Mémoire présenté à l'Université du Québec à Trois-Rivières comme exigence partielle de la maîtrise en physique offerte par extension à l'Université du Québec à Montréal en vertu d'un protocole d'entente avec l'Université du Québec à Trois-Rivières". CaQTU CaQTU Bibliogr. : f. 74.
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Garcia, André Felipe. "Transição quiral na matéria de quarks magnetizada." Florianópolis, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/100419.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em FísicaMade available in DSpace on 2013-06-25T19:00:58Z (GMT). No. of bitstreams: 1 311322.pdf: 5230146 bytes, checksum: 30f7940fb6addda231c03960c74fb1ca (MD5)
A física de altas energias é um dos campos de pesquisa mais interessantes da física e de maior atividade atualmente, abrangendo fenômenos físicos que vão desde cosmologia até a física de partículas elementares. Nesta última, sua atuação se dá principalmente nos modernos aceleradores de partículas, como o Relativistic Heavy Ion Collider (RHIC) e o Large Hadron Collider (LHC), onde feixes de partículas colidem entre si produzindo inúmeras outras partículas. A Cromodinâmica Quântica é a teoria que descreve a força nuclear forte entre quarks e glúons, que são os formadores dos hádrons e estão confinados no interior dos mesmos. Entretanto, existe a possibilidade de que em regimes de altas energias caracterizados por temperaturas e/ou densidades elevadas estes quarks e glúons passem da fase hadrônica para uma fase desconfinada representada pelo plasma de quarks e glúons. Essa transição de fase tem inúmeras implicações experimentais (algumas delas sendo atualmente testadas no RHIC e no LHC), além de ser importante na descrição dos estágios iniciais do universo e da matéria que compõe as estrelas de nêutrons. Além disso, recentemente tem-se argumentado que espectadores (partículas periféricas que não se envolvem diretamente na colisão) em colisões não centrais de íons pesados podem gerar fortes campos magnéticos na região de colisão, o que pode influênciar as características da transição de fase. No entanto, devido as dificuldades técnicas em se trabalhar diretamente com a QCD, o uso de modelos efetivos que apresentam algumas propriedades e simetrias desta teoria tem crescido significativamente, mostrando-se uma boa alternativa para contornar estas dificuldades. Um dos modelos mais conhecidos é o modelo de Nambu--Jona-Lasinio (NJL), que, na sua versão mais simples, trata a interação entre quarks up e down como sendo pontual, isto é, sem a participação de gluons. Isto facilita em muito os cálculos envolvidos, apesar de restringir o uso do modelo a escalas de energia que sejam compatíveis com esta aproximação. Nesta dissertação faremos uso da versão SU(2) do modelo de NJL em temperaturas e densidades finitas para estudar a transição quiral na matéria de quarks com e sem a influência de um campo magnético externo. Estudaremos com maiores detalhes o diagrama de fases associado ao modelo, em especial a região da transição de primeira ordem onde há coexistência de fases. Veremos como o campo magnético altera a temperatura pseudo-crítica no crossover, o potencial químico de coexistência em baixas temperaturas e a localização do ponto crítico no diagrama de fases. Até o momento a maioria dos trabalhos relacionados com este tema estão restritos ao estudo dos efeitos do campo magnético no plano $T-\mu$. Neste trabalho damos um passo a frente, investigando também os efeitos do campo magnético sobre algumas grandezas termodinâmicas como a pressão, entropia, densidade bariônica, densidade de energia, susceptibilidade do número de quarks, anomalia do traço e curvas isentrópicas. Um dos resultados mais interessantes da dissertação é uma inesperada "deformação" no diagrama de coexistência de fases no plano $T-\rho$ devido às oscilações na curva de coexistência causadas pelo campo magnético. Este comportamento pode ser entendido em termos do preenchimento dos níveis de Landau em temperaturas baixas.
High energy physics is one of the most interesting research fields of physics in activity nowadays, covering physical phenomena from cosmology to elementary particle physics. Within the latter, high energy physics is present in modern particle accelerators such as the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), where particle beams collide producing several other particles. Quantum Chromodynamics (QCD) is the theory that describes the strong nuclear force among quarks and gluons, which form the hadrons and are confined in their interior. However, there is the possibility that in high energy regimes characterized by high temperatures and/or densities these quarks and gluons undergo a phase transition, changing from the hadronic phase to a deconfined phase represented by the quarkgluon plasma. This phase transition has several experimental implications (some of them being tested in the RHIC and in the LHC), being also important in the description of the early stages of the universe and in the study of the matter in neutron stars. Furthermore, it has been argued in recent years that spectators (particles at the edge of the beam that do not get involved directly in the collision) in non-central heavy ion collision are responsible for creating a strong magnetic field that could affect the features of the phase transitions. However, due to tecnical difficulties in dealing with QCD, the use of less fundamental theories that mimic some of the properties and symmetries of the original theory has growth significantly, being a good alternative to face those difficulties. One of the most popular models is the Nambu{Jona-Lasinio (NJL) model, which, in its simplest version, treats the interaction between up and down quarks as being pontual, with no gluon exchange. This makes calculations a lot easier to perform, but restricts the use of the model to energy scales onsistent with this approximation. In this dissertation we make use of the SU(2) NJL model at finite temperatures and densities in order to study the chiral transition in quark matter under the influence or not of an external magnetic field. We study the phase diagram of the model in detail, paying special attention to the first order transition, where the symmetric and non symmetric phases can coexist. We investigate how the magnetic field affects the crossover pseudocritical temperature, the coexisting chemical potential at low temperatures and the location of the critical end point in the phase diagram. So far, most of the works related to this theme are restricted to the investigation of the magnetic field over the T - u plane only. We take a step forward in this direction, investigating the effects of the magnetic field over some thermodynamic quantities such as the pressure, entropy, baryonic density, energy density, quark number susceptibility, trace anomaly and the isentropic curves or adiabats. One of the most interesting results of this work is the \deformation" of the coexistence phase diagram in the T - u plane caused by the oscillations of the coexistence curve due to the magnetic field. This behavior may be explained in terms of the filing of the Landau levels at low temperatures.
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Chan, Ying-kit. "Strange star cooling." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B3138254X.
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Chan, Ying-kit, and 陳英傑. "Strange star cooling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B3138254X.
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Veiga, J. S. [UNESP]. "Propriedades da matéria nuclear em modelos de quarks constituintes." Universidade Estadual Paulista (UNESP), 1996. http://hdl.handle.net/11449/132865.
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Lees, Jean-Pierre. "Recherche du quark Top dans l'expérience UA1 par l'étude des événements contenant un électron isolé de grande impulsion transverse accompagné de jets." Chambéry, 1987. http://www.theses.fr/1987CHAMS003.
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Peset, Martín Clara. "Effective field theories for heavy quarkonia and hydrogen-like bound states." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/385205.
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En esta disertación nos concentramos en el estudio de la física de estados débilmente ligados formados por dos fermiones pesados de masas diferentes. Los describimos en términos de teorías de campos efectivas, específicamente las teorías pNRQED y pNRQCD. En este contexto, calculamos los potenciales hasta cuarto orden de expansión en dos sistemas distintos: átomos hidrogenoides y quarkonium pesado. Aplicamos estos resultados para extraer algunos de los niveles de energía asociados.
En la primera parte de la tesis, obtenemos una expresión independiente de modelo para el efecto Lamb en hidrógeno muónico. Esta expresión incluye los principales términos logarítmicos de orden (mα^6 ), así como los principales efectos hadrónicos hasta orden (mα^5 m²/Λ²). Como característica notable, nuestro análisis incluye la determinación de las funciones de estructura del tensor de Compton virtual hacia adelante, tanto dependiente como independiente del espín, a orden p³ en la teoría HBET e incluyendo los efectos de la partícula Delta. A partir de estos resultados obtenemos las principales contribuciones hadrónicas a los coeficientes de Wilson de los operadores de cuatro fermiones en el lagrangiano leptón-protón de NRQED. El coeficiente independiente de espín da lugar a una predicción pura de la contribución de intercambio de dos fotones al efecto Lamb del hidrógeno muónico, el cual es la mayor fuente de incertidumbre de nuestro cálculo. El uso de teorías de campos efectivas ayuda a organizar el cálculo, de tal forma que se puede establecer claramente la exactitud paramétrica del resultado. Más allá de esto, revisamos en el contexto de NRQED todas las contribuciones a la variación de energía a orden (α^5), así como aquellas que escalean como (α^6) veces logaritmos. Con nuestra determinación final del efecto Lamb, obtenemos el valor del radio eléctrico del protón en una forma independiente de modelo. El valor que obtenemos está a distancia de 6.8σ del valor de CODATA.
En la segunda parte de esta tesis, determinamos los potenciales 1/m y 1/m² del quarkonium pesado independientes del espín con orden de precisión α³ y α² respectivamente. Discutimos en detalles diferentes métodos para calcular estos potenciales, y mostramos explícitamente su equivalencia. En particular, obtenemos por primera vez, los potenciales 1/m y 1/m² manifiestamente invariantes de gauge en términos de lazos de Wilson con precisión de segundo orden de expansión. Como aplicación de estos resultados, derivamos la expresión teórica para el espectro del Bc en el límite de acoplamiento débil a cuarto orden de expansión.In this dissertation, we concentrate on the physics of weakly bound states made of two heavy fermions with different masses. Their description is performed in the framework of effective field theories (EFTs), specifically pNRQED and pNRQCD. We compute the potentials up to next-to-next-to-next-to leading order (N³LO) for two systems: hydrogen-like atoms and heavy quarkonia. We apply our results to the extraction of some associated energy levels. In the first part of this thesis, we obtain a model independent expression for the muonic hydrogen Lamb shift. This expression includes the leading logarithmic terms of order (mα^6 ) as well as the leading hadronic effects of order (mα^5 m²/Λ²). Most remarkably, our analysis include the determination of the spin-dependent and spin-independent structure functions of the forward virtual-photon Compton tensor of the proton to order p³, using HBET and including the Delta particle. Using these results we obtain the leading hadronic contributions to the Wilson coefficients of the lepton-proton four fermion operators in NRQED. The spin-independent coefficient yields a pure prediction for the two-photon exchange contribution to the muonic hydrogen Lamb shift, which is the main source of uncertainty in our computation. The use of EFT crucially helps us organizing the computation, in such a way that we can clearly address the parametric accuracy of our result. Furthermore, we review in the context of NRQED all the contributions to the energy shift of order (α^5), as well as those that scale like (α^6) times logarithms. With our final determination of the Lamb shift, we obtain the proton charge radius in a model independent way. The value we obtain is 6.8σ away from the CODATA value. In the second part of this thesis, we determine the 1/m and 1/m² spin-independent heavy quarkonium potentials in the unequal mass case with order α³ and order α² accuracy, respectively. We discuss in detail different methods to calculate such potentials, and explicitly show the equivalence among them. In particular we obtain, for the first time, the manifestly gauge invariant 1/m and 1/m² potentials in terms of Wilson loops with next-to leading order (NLO) precision. As an application of our results we derive the theoretical expression for the Bc spectrum in the weak-coupling limit to N³LO.
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Lapoint, Cary Robert 1970. "Heavy quarkonia production in e⁺ e⁻ collisions at the Z pole." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50420.
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Roy, Christelle. "L'Etrangeté du Plasma de Quarks et de Gluons." Habilitation à diriger des recherches, Université de Nantes, 2005. http://tel.archives-ouvertes.fr/tel-00011076.
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A l'instar des trois autres expériences auprès du collisionneur RHIC (Relativistic Heavy Ion Collider) du Brookhaven National Laboratory près de New York, STAR (Solenoidal Tracker At RHIC) est entièrement consacrée à la mise en évidence de cet état particulier de la matière nucléaire prédit par les calculs de QCD (Quantum ChromoDynamics) sur réseau : le plasma de quarks et de gluons (QGP pour Quark Gluon Plasma). Cet état, supposé être celui de l'Univers quelques fractions de secondes après le Big Bang, consisterait d'après sa définition originelle de 1975, en une matière dans laquelle quarks et gluons seraient déconfinés, sans interaction. Il pourrait être créé en laboratoire lors de collisions d'ions lourds réalisées à des énergies ultra-relativistes afin d'atteindre des températures et densités d'énergie extrêmes.Après quasiment 20 ans de recherche auprès des différents accélérateurs de particules américains et européens, le CERN annonce le 10 février 2000 au cours d'une conférence de presse, la mise en évidence expérimentale d'un état particulier de la matière nucléaire, compatible avec la formation d'un QGP, sans pouvoir toutefois le caractériser pleinement. Les expériences du RHIC ont alors pris le relais. Aujourd'hui, au travers une pléthore de résultats nouveaux et parfois bien surprenants, il apparaît de façon de plus en plus certaine, qu'effectivement un état atypique de matière nucléaire a été créé à RHIC et notre vision du QGP comme un gaz parfait de partons n'interagissant que très faiblement, a depuis changé. Un nouvel acronyme a été défini : sQGP pour Strongly Interacting QGP.
Pour parvenir à cette observation, il a fallu passer par la caractérisation même de l'évolution des collisions d'ions lourds, du point de vue chimique et dynamique, en comparant les phénomènes des collisions d'ions lourds pour lesquelles les conditions devraient être réunies pour former un QGP à des collisions d'énergies moindres ou de systèmes plus légers qui ne peuvent permettre cette formation. Le QGP est en effet produit de manière beaucoup trop furtive pour pouvoir le sonder directement. Mon mémoire d'Habilitation à Diriger des Recherches présente les résultats des analyses que j'ai menées et qui ont contribué à la mise en évidence de la formation d'un état nouveau au RHIC et à cette nouvelle vision du plasma. Les stigmates du QGP ont été recherchés avec les particules contenant des quarks étranges : les résonances de particules simplement étranges et les baryons doublement étranges.
La production des résonances étranges Lambda(1520) apporte en effet des informations sur la phase d'hadronisation du plasma (lorsque les partons se recomposent en hadrons) : selon leur observation ou non, il pourrait être possible de caractériser le freeze-out chimique (instant où les interactions inélastiques cessent et la composition chimique du système est figée), le freeze-out cinétique (instant où les interactions élastiques cessent et les particules n'interagissent plus), si ces deux freeze-out coïncident ou si, au contraire ils sont séparés dans le temps et de combien. L'idée est la suivante : les Lambdas(1520) se désintègrent quasiment instantanément en un proton et un kaon. Par conséquent, si le temps entre les freeze-out chimique et cinétique est long, les produits de désintégration de ces particules peuvent être absorbés dans le milieu dense qui a été créé. En revanche, si les deux freeze-out coïncident ou sont très proches, les produits de désintégration ne sont pas affectés et la particule mère, c'est-à-dire la résonance, peut être identifiée. Ainsi, en mesurant les taux de production de ces particules dans les collisions proton–proton pour lesquelles les deux freeze-out coïncident, et en comparant les taux obtenus dans les collisions Au–Au, à l'énergie nominale du RHIC, il est apparu qu'effectivement, au moins 4 fm/c séparent les deux freeze-out dans les collisions Au–Au. Cette conclusion constitue une étape importante dans la compréhension des collisions d'ions lourds ultra-relativistes et du comportement de la matière dans des conditions extrêmes. Cette analyse est apparue comme originale au sein de la collaboration STAR, étant la première étude sur les résonances étranges. Des algorithmes spécifiques ont dû être mis au point et sont largement utilisés au sein de la collaboration qui depuis étudie de nombreuses autres résonances ou recherche des objets plus exotiques.
La production des baryons étranges a été largement investiguée les années passées car une augmentation « anormale » des taux de production est attendue si un QGP est formé. Les expériences du CERN ont observé effectivement une surproduction de l'étrangeté dans les collisions Pb–Pb mais n'ont pu conclure de manière décisive quant à une formation éventuelle d'un plasma car ces résultats pouvaient être également reproduits par des modèles de gaz de hadrons. Nous avons mené une analyse similaire avec les données de STAR en comparant les taux de production des Xi, baryons doublement étranges, dans les collisions proton–proton et Au–Au à sqrt(s_NN) = 200 GeV. Là aussi, les résultats sont demeurés ambigus. Ainsi, ces résultats ont conduit un certain nombre de physiciens à ne plus considérer les taux de production de particules étranges comme une signature robuste de la formation d'un QGP. En revanche, l'étrangeté est revenue sur le devant de la scène, de façon plus indirecte donnant des informations très diverses et sur les différentes étapes de la collision.
Les Xi ont révélé tout d'abord que le système créé à l'énergie nominale du RHIC serait en équilibre thermique et chimique et que les températures de freeze-out chimique sont proches de la température de déconfinement prédite par QCD. Nous avons également étudié les phénomènes dynamiques collectifs, appelés flot, qui naissent des interactions entre constituants et se traduisent par une émission de matière dans des directions privilégiées de l'espace de phase. En accord avec leurs faibles sections efficaces d'interaction, les Xi semblent émis bien plus tôt que les particules plus légères. Toutefois, le fait que ces baryons subissent un flot important, laisse supposer qu'elles auraient développé un flot, donc qu'elles auraient été soumises à des interactions, avant la phase d'hadronisation, autrement dit, dans une phase partonique. Les partons subiraient donc des interactions résiduelles, contrairement à ce que préconisaient les théoriciens du milieu des années soixante-dix.
Par ailleurs, en 2003, les quatre expériences du RHIC ont révélé conjointement la mise en évidence du phénomène de jet-quenching dans les collisions d'ions lourds : il traduit une diminution de la production de particules chargées de très haute impulsion transverse s'expliquant par la perte d'énergie des partons dans un milieu très dense. Nous avons réalisé cette analyse en considérant les X et montré que non seulement ces baryons subissent un jet-quenching mais aussi qu'ils ont un comportement différent de celui des mésons. Une dépendance des phénomènes dynamiques au type de particules a ainsi été mise en évidence en accord avec les modèles de coalescence préconisant que les hadrons se forment à partir de la recombinaison des quarks. Là aussi, émergence des partons comme degrés de liberté pertinents.
A partir de ces résultats entre autres, certains théoriciens affirment la découverte du QGP à RHIC mais les expérimentateurs sont plus prudents et désirent auparavant confirmer et enrichir leurs résultats par l'étude d'autres observables qui viendraient corroborer ces observations. Ces années ont été particulièrement stimulantes par l'évolution de nos connaissances grâce aux formidables résultats produits par les quatre expériences du RHIC. Les « vielles » signatures ont fait peau neuve se transformant en sondes nouvelles et riches en informations originales. La conception du QGP a évolué : il ne s'agit plus d'un gaz parfait constitué de partons évoluant librement mais d'un sQGP.
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Perret, Pascal. "Tests électrofaibles du Modèle Standard et quarks lourds." Habilitation à diriger des recherches, Université Blaise Pascal - Clermont-Ferrand II, 2002. http://tel.archives-ouvertes.fr/tel-00001683.
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Andrieux, Vincent. "Polarisation of quarks and gluons inside the nucleon." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112244/document.
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Cette thèse présente un travail relatif à l'étude de la structure en spin longitudinal du nucléon. Le but est de déterminer la contribution des constituants du proton, quarks et gluons, à la formation de son spin 1/2. L'analyse s'appuie sur les données de l'expérience COMPASS qui bénéficie d'un faisceau de muons polarisés à 200 GeV diffusé sur les protons polarisés d'une cible d'ammoniac (NH₃) de 1,2 m de long. On mesure l'asymétrie de spin longitudinal des sections efficaces de diffusion profondément inélastique. On extrait la fonction de structure en spin du proton, g₁p, étendant la couverture cinématique mondiale à des régions inexplorées jusqu'à maintenant (0,0036 < x < 0,57; 1,03 < Q² (GeV/c)² < 96 et 23 < W² (GeV/c)² < 320). Les résultats, d'une grande précision statistique, sont inclus dans une analyse des données mondiales de g₁p, g₁d et g₁n (proton, deutéron et neutron) au 2ème ordre de QCD afin de paramétrer les distributions de quarks et de gluons polarisés. L'étendue de la couverture cinématique en x et Q² des données mondiales de g₁, un élément déterminant pour la sensibilité à la polarisation des gluons ΔG, s'avère trop limitée pour constituer une extraction précise de celle-Ci. Néanmoins, l'analyse QCD permet de déterminer la contribution du spin des quarks au spin du proton à 0.26<ΔΣ<0.33 à Q² = 3 (GeV/c)² dans le schéma MSbar. L'étude montre que l'incertitude principale sur ΔΣ est liée au choix des formes fonctionnelles utilisées dans la régression des données. Enfin, la règle de somme de Bjorken, qui constitue un test de QCD, est vérifiée avec une précision de 9% en utilisant les données de COMPASS uniquementThe work presented in this thesis is related to the study of the longitudinal spin structure of the nucleon. The aim is to determine the contribution to the spin 1/2 of the proton in terms of its constituents, quarks and gluons. The analysis is performed on the data taken with the COMPASS experiment, which benefits from a polarised muon beam at 200 GeV scattered off polarised protons from an ammonia target of 1.2 m long. The double longitudinal spin asymmetry of deep inelastic scattering cross-Section. The spin-Dependent structure function of the proton g₁p is derived from these measurements, which extend the kinematic world coverage to unexplored region so far (0,0036 < x< 0,57; 1,03 < Q² (GeV/c)² < 96 and 23 < W² (GeV/c)² < 320).The results obtained with a high statistical precision are included in a Next-To-Leading order QCD analysis of world g₁p, g₁d and g₁n (proton, deuteron and neutron) data to parametrise the polarised quark and gluon distributions. The g₁ world coverage of the x and Q² kinematic domain, which is a key point in the sensitivity to the gluon polarisation ΔG, turns out to be too limited for an accurate ΔG determination. Nevertheless, the QCD analysis allows to determine the quark spin contributions to the proton spin to 0.26<ΔΣ<0.33 at Q² = 3 (GeV/c)² in the MSbar scheme. The dominant uncertainty on ΔΣ is related to the choice of functional forms assumed in the fit. Finally, the Bjorken sum rule, which constitutes a fundamental test of QCD, is verified on the COMPASS data alone with a precision of 9%
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Mello, Cedrick Miranda. "Estudo da detecção de quarks top no LHC." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-08032013-122617/.
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Este trabalho consistiu em analisar a possibilidade de verificação da violação de sabor em correntes neutras intermediadas por glúons de Kaluza-Klein (GKK) através do modelo de dimensões extras compactas e curvas. Este introduz a possibilidade de violação de sabores em correntes neutras através de processos do tipo próton/próton em top/anti-quark c. Inicialmente estudamos o comportamento de jatos com altos momentos transversos (da ordem de 300 GeV) e suas subestruturas. Após isto, estudamos a detecção do quark top através dos algoritmos HEPTopTagger e Johns Hopkins (fizemos uma breve comparação entre eles). Por último, propusemos duas maneiras de encontrar os GKK. Uma delas, através da procura de somente quarks top. A outra, através da procura de um quark top e um jato sem subestrutura (algoritmo do tipo TJ). Pudemos ver que a possibilidade de encontrar o fenômeno de violação de sabores é acessível (a razão S/B da ordem de 0,1) para ambos os casos de massa analisados através do algoritmo do tipo TJ.This study was to examine the possibility of verifying the violation of flavor in neutral currents mediated by Kaluza-Klein gluons (GKK), in which it was introduced by compact warped extra dimensions. The possibility of violation of flavors in neutral currents occurs through processes like proton/proton into quark top/ antiquark charm. Initially we studied the behavior of jets with high transverse momentum (the order of 300 GeV) and its substructures. After this, we studied the detection of the top quark via HEPTopTagger and Johns Hopkins algorithms (we did a brief comparison between them). Finally, we proposed two ways to find the GKK. One of them, by searching for only quark top. The other, by looking for a quark top and a jet without substructure (algorithm of TJ type). We could see that the possibility of encountering the phenomenon of violation of flavors is accessible (the ratio S/B is the order of 0.1) in both cases of mass analyzed by TJ type algorithm.
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Motta, Théo Ferraz. "Matéria de Quarks fria sob campo magnético forte." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-25052017-105222/.
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Esta dissertação apresenta uma breve revisão introdutória de alguns aspectos importantes de astrofísica nuclear e da fenomenologia do plasma de quarks e glúons a baixas temperaturas. Acredita-se que tal estado da matéria existe no núcleo de estrelas de nêutron e possivelmente de outros objetos compactos em astrofísica. Uma equação de estado para tal sistema é derivada incluindo as influências dos condensados de glúon e do campo magnético que também é uma característica importante das estrelas de nêutron. Finalmente, essa equação de estado é aplicada para o estudo de estrutura estelar de estrelas compactas e alguns resultados importantes são discutidos.This dissertation presents a brief introductory overview of some key aspects of nuclear astrophysics and of the phenomenology of the quark gluon plasma at cold temperatures which is believed to exist inside the core of neutron stars and possible other compact astrophysical objects. An equation of state for this state of matter is derived incluing the influence of gluon condensates and the magnetic field which is also an important characteristic of neutron stars. And finally this equation of state is applied to the study of compact stellar structure and some important results are discussed.
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Carvalho, Sheyse Martins de. "Efeitos do confinamento na matéria de quarks supercondutora." Instituto Tecnológico de Aeronáutica, 2010. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1564.
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No regime de altas densidades, os modelos de quarks com geração dinâmica de massa prevêem que a matéria estranha de quarks pode aparecer em duas fases, uma fase quiral simétrica e outra quebrada que não é absolutamente estável. A altas densidades, a abundância dos quarks u, d e s é a mesma na fase quiral simétrica e não há elétrons. Estas duas propriedades também estão presentes numa nova fase supercondutora que deve ocorrer na QCD a altas densidades, conhecida como fase fechada de cor e sabor (CFL). Isto sugere que a matéria estranha a altas densidades possa fazer uma transição para fase CFL, na qual a energia é diminuida pelo emparelhamento BCS dos quarks. Nesta tese fazemos um estudo numa versão completa do modelo cromodielétrico (CDM) onde implementamos o emparelhamento dos quarks e analisamos a fase supercondutora de cor e sabor. Para investigar o efeito do confinamento nesta fase, derivamos uma lagrangeana efetiva para o emparelhamento, expandindo-a em torno do valor do campo médio ? do campo confinante do CDM e em ordem mais baixa. A constante efetiva da interação de emparelhamento depende explicitamente de ?. As equações de gap auto-consistentes no canal escalar e vetorial são obtidas e resolvidas numericamente para diferentes valores dos parâmetros do CDM. Para o potencial quártico usado nos cálculos, na solução quiral, obtida para grandes valores do campo de confinamento e pequenos valores da massa do quark, os quarks não emparelham. Para a solução quiral quebrada, onde ? é pequeno e os quarks são massivos, encontramos emparelhamento. Mostramos que o canal vetor do gap é mais fraco que o escalar, e o gap de emparelhamento vetorial pode chegar até 120 MeV para altas densidades.
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Tran, Huong Lan. "Recherche de quarks lourds avec le détecteur ATLAS." Paris 7, 2013. http://www.theses.fr/2013PA077274.
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Une recherche de quarks lourds est presentée dans cette these. Elle est composée de trois parties principales. Dans la première partie est presentée l'étude du facteur de qualité Q pour les calorimètres à Argon liquide de ATLAS. Le facteur Q est une quantité définie pour estimer l'accord entre le signal mesuré et la prédiction. Dans le cas où la prédiction n'est pas parfaite, il peut induire un rejet de bons signaux. La prédiction peut cependant être corrigée en utilisant des signaux purs d'ionisation selectionnés dans les données. Les résultats montrent une bonne amélioration: La correction de la prédiction a permis de réduire la dépendance du facteur Q avec l'énergie du signal. Les nouvelles prédiction des formes de signal corrigées par les résidus ont été intégrées à la base de données d'ATLAS pour être utilisées lors de futures campagnes de reconstruction des données. La deuxième partie est le coeur de la thèse: le développement d'une analyse de recherche de quarks lourds innovante. Cette analyse est réalisée en trois étapes. Dans la première étape, une méthode de maximum de vraisemblance est utilisée pour déterminer le nombre d'événements de signal éventuellement présent dans les données. Un excès d'environ 2a est observé: Ns= 82 +39. Dans la deuxième étape, la méthode Plot est utilisée pour construire la distribution —36 s de variables de contrôle, par exemple la masse invariante de trois jets. Le résultat donne des distributions compatibles avec l'hypothèse nulle, qui nuance l'excès obtenu. Enfin dans la dernière étape, une méthode statistique a été développée pour combiner l'information des deux premières étapes. La méthode aboutit à un résultat compatible avec celui de l'approche standard adoptée dans ATLAS; il exclut des quarks lourds de mass mt, < 520 GeV/c2 (600 GeV/c2 attendu) à 95 % CL en utilisant 4. 7 fb--, de données à 7 TeV. La dernière partie de cette thèse présente ma contribution au Groupe Exotics sur la recherche de quarks de type vecteur, où j'ai été impliquée dans l'analyse de canal dilepton de même signe; j'ai également contribué la mise en place de la combinaison des differentes analyses. Un quark vecteur de charge +2/3 (-1/3) de mass inférieure à 550 (450) GeV/c2 est exclu quelque soit son rapport d'embranchement en tH, tZ ou bW (bH, bZ, tW)A search for heavy quarks is presented in this thesis. It is organized in three main parts. In the first part presented the study on the quality factor for the liquid Argon calorimeters of ATLAS. The Q-factor is a quantity defined to estimate the agreement between the measured and the predicted pulse shape. In case the prediction is not perfect, it can lead to spurious rejection of good signal. The prediction however can be corrected using a pure sample of signal selected from the data. The results show a clear improvement: correcting the prediction helped to reduce the dependence of the Q-factor on the signal's energy. The new pulse shape predictions have been stored in the ATLAS database to be used in the next data reprocessing. The second part is the heart of the thesis: development of a novel analysis to search for heavy quarks. This novel approach is performed in three steps. In the first step, a Likelihood fit method is built to determine the number of signal events in the data. An excess w. R. T. Expectation in absence of signal events is observed: N = 82+39. In the second step, the Plot method is used to reconstruct distributions S-36 s of control variables, for instance the invariant mass of three jets. The result shows distributions compatible with the null hypothesis. Finally in the last step, a statistical method has been developed to combine the output of the first two steps. The method leads to a result compatible with the standard approach in ATLAS; It excludes heavy quarks with masses mtbelow 520 GeV/c2 (600 GeV/c2 expected) at 95 % CL using 4. 7 fb-i of 7 TeV data. The last part of this thesis presents my contribution to the Exotics Group on the search for vector-like quarks, where I was involved in the same-sign dilepton channel analysis; I also contributed to the combination of various analyses. As a summary, a vector-like quark of charge +2/3 (-1/3) with mass smaller than 550 (450) GeV/c2 is excluded regardless of its branching ratio to tH, tZ or bW (bH,bZ,tW )
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Khamseh, Ava. "Lattice phenomenology of heavy quarks using dynamical fermions." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28855.
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The Standard Model of particle physics is believed to be only the low energy limit of a more fundamental theory. In order to determine its range of validity, a major part of theoretical and experimental efforts in physics is dedicated to precision tests of the Standard Model. Lattice QCD is a non-perturbative, first-principles approach to Quantum Field Theory. It plays an important role in flavor physics by providing calculations of non-perturbative strong interaction contributions to weak processes involving quarks. Measurements of hadronic quantities can be used to constrain the Standard Model as well as theories Beyond the Standard Model. The first part of this thesis contains theoretical developments regarding non-perturbative renormalization. A new renormalization scheme, RI/mSMOM, for fermion bilinear operators in QCD at non-vanishing quark mass is presented. In order to investigate the properties of the mSMOM scheme, an explicit one-loop computation in perturbation theory using dimensional regularization is performed. Numerically, vertex functions are generated on the lattice, with an appropriate projector, based on the RI/SMOM scheme and the renormalization factors are extracted. Quantities measured include renormalization of the axial current ZA, required to renormalize the axial current entering the computation of the decay constant and the renormalization of the bag parameter. The second part of this report focuses on flavor physics phenomenology on the lattice. It presents results of the first run of the RBC/UKQCD charm project with (2+1)-flavor Domain Wall fermions. Observables and matrix elements are measured on lattices with Iwasaki gauge action. There are two ensembles at the physical point with inverse lattice spacings 1.73 and 2.36 GeV and a third finer ensemble at 2.76 GeV as well as four other auxiliary ensembles with smaller volumes and heavier pion masses which are used to perform the continuum extrapolations. The quantities measured in the region of the charm quark mass are meson masses, decay constants, the matrix element of the OV V +AA operator, the neutral D-meson mixing parameter B and the SU(3) breaking ratio ξ.
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Medina, Tulio Eduardo Restrepo. "Geração radiativa de repulsão vetorial para quarks leves." reponame:Repositório Institucional da UFSC, 2014. https://repositorio.ufsc.br/xmlui/handle/123456789/129306.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2014Made available in DSpace on 2015-02-05T20:56:09Z (GMT). No. of bitstreams: 1 330269.pdf: 2723044 bytes, checksum: acc5bb1f16ab0d07a08b676e16f1ea63 (MD5) Previous issue date: 2014
Abstract: We apply a non-perturbative analytical method, known as the Optimized PerturbationTheory (OPT), to the Polyakov-Nambu-Jona-Lasinio (PNJL) model in order to investigate physical quantities associated with the QCD phase transitions. We consider the Taylor expansion of the pressure in powers of µ/T obtaining the second cumulant (c2) which is associated to the quark number susceptibility. We discuss how the OPT nite Nc radiative (quantum) corrections induce a contribution to the pressure which behaves as a vector repulsion even when such a channel is absent in the original classical potential. Our results are then compared with the ones furnished by lattice QCD simulations and by the large-Nc approximation showing that, physically, the OPT results resemble those furnished by the latter approximation when a repulsive vector channel is explicitly included in the classical potential. In this case, both approximations fail to correctly describe the Stefan-Boltzmann limit at high temperatures. We discuss how this problem can be circumvented by taking the couplings to be temperature dependent so as to simulate the phenomenon of asymptotic freedom. Since this is the first time the OPT is applied to the PNJL we also discuss many technicalities associated with the evaluation of two loop (exchange) diagrams.
Neste trabalho o método analítico não perturbativo conhecido como Teoria de Perturbação Otimizada (OPT) é aplicada ao modelo de Polyakov-Nambu-Jona-Lasinio (PNJL) para que quantidades físicas, associadas com as transições de fase da QCD, possam ser calculadas. A expansão da pressão em potências de µ/T é considerada para obter o segundo cumulante (c2) que é uma quantidade relacionada com a susceptibilidade do número de quarks. Primeiramente discutimos como as correções radiativas de Nc finito geradas pela OPT produzem uma contribuição que se comporta como um termo vetorial repulsivo mesmo quando este tipo de canal está ausente no potencial clássico original. Em seguida, nossos resultados são comparados com aqueles fornecidos pelas simulações na rede e também pela aproximação de Nc grande(LN). Fisicamente, os resultados da OPT são similares aqueles fornecidos pela aproximação LN quando um canal vetorial repulsivo é explicitamente incluido no potencial clássico. Neste caso, nenhuma destas aproximações analíticas produz corretamente o limite de Stefan Boltzmann para altas temperaturas. Contudo, nossos resultados sugerem como estes problemas podem ser contornados tomando-se as constantes de acoplamento como sendo dependentes da temperatura, de maneira que o fenômeno da liberdade assimptótica possa ser simulado. Esta é a primeira vez que a OPT é aplicada ao modelo de PNJL e por isto vários aspectos técnicos relacionados com o cálculo de diagramas de dois laços são também aqui apresentados.
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Bousson, Nicolas. "Recherche de nouveaux quarks lourds avec l'expérience ATLAS au LHC. Mise en oeuvre d'algorithmes d'identification de jets issus de quarks b." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4101/document.
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L'hypothèse d'une quatrième famille de fermions –les particules de matière décrites au sein du Modèle Standard (MS) de la physique des particules– est un des plus simples modèles de nouvelle physique encore non exclu et accessible au démarrage du LHC – le plus puissant collisionneur hadronique au monde depuis 2009. Cette thèse s'intéresse à la production d'une paire de quarks t' se désintégrant chacun via Wb. La recherche se focalise sur le domaine des très hautes masses, où la production peut être distinguée de la production de bruit de fond d'une paire de quark top en exploitant la cinématique des produits de désintégration des collisions p-p produites au centre du détecteur ATLAS. Nous présentons une stratégie originale exploitant la collimation des produits de la désintégration des bosons W de grande impulsion transverse, permettant leur reconstruction explicite. L'analyse s'appuie sur un travail de mise en oeuvre des algorithmes d'identification des jets résultants de la fragmentation des quarks de saveur b. L'étiquetage-b permet à l'expérience ATLAS d'améliorer la (re)découverte du MS, et la sensibilité à la nouvelle physique. Il sera ainsi d'une grande importance pour les futures années d'opération du LHC, raison pour laquelle nous présentons une étude de prospective de ses performances attendues avec l'extension du détecteur à pixels d'ATLAS dénommée IBL. Notre recherche de quark t' a permis d'établir une limite inférieure à la masse du quark t' de 656 GeV à partir des 4.7 fb^−1 de données 7 TeV collectées en 2011, ce qui est la meilleure limite à ce jour en recherche directe, avec également une interprétation dans le cadre du modèle de quarks dits vecteursThe hypothesis of a fourth generation of fermions – the matter particles described in the Standard Model (SM) of particle physics – is one of the simplest model of new physics still not excluded and accessible at the start of the Large Hadron Collider (LHC) – the world most powerful hadron collider since 2009. We search for the pair production of up-type t' quarks decaying to a W boson and a b-quark. The search is optimized for the high quark mass regime, for which the production can be distinguished from the top background by exploiting kinematic features of the decay products arising from the proton-proton collisions occurring at the center of the ATLAS detector. We present a novel search strategy reconstructing explicitly very high-pT W bosons from their collimated decay products. The analysis benefits from the commissioning of algorithms intended to identify jets stemming from the fragmentation of b-quarks. These algorithms are based on the precise reconstruction of the trajectory of charged particles, vertices of primary interaction and secondary vertices in jets. The b-tagging ability allows for ATLAS to improve the (re)discovery of the SM, and the sensibility to new physics. It will hence play an important role in the future of the LHC, the reason why we study the expected performance with an upgrade of the ATLAS pixel detector, called IBL and currently under construction. Our search of t' quark, using 4.7 fb^−1 of the 7 TeV data collected in 2011, has resulted in the world most stringent limit, excluding t' masses below 656 GeV, with also an interpretation in the framework of vector-like quarks
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Gimenez, Diógenes Domenicis. "Estudo da coincidência elétron-jato em colisões próton-próton e próton-núcleo no experimento ALICE." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-13032018-134433/.
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Esta tese apresenta um estudo inédito da distribuição de jatos correlacionados com elétrons provenientes de decaimentos de quarks pesados (HFe), reconstruídos e selecionados com o ALICE (A Large Ion Collider Experiment, em inglês). Os observáveis foram medidos em colisões pp com energia do centro de massa s = 8 TeV e em colisões p-Pb a sNN = 5.02 TeV, no LHC (Large Hadron Collider, em inglês). Estudar os quarks pesados formados durante as colisões relativísticas entre íons pesados é uma importante maneira para estudar o meio formado, conhecido como QGP (Quark Gluon Plasma, em inlgês). Isso se deve ao fato de que eles são criados no início da colisão e, portanto, interagem com o QGP durante toda sua existência. Em seguida, tais quarks fragmentam em mésons que podem decair, via canal semi-leptônico, em elétrons (e pósitrons). Esses léptons podem ser utilizados para indicar a existência de um quark pesado e permitir o estudo do QGP. Os processos de espalhamento duro, fragmentação e decaimento dão origem a diversas partículas que estão colimadas em uma região espacial, a que chamam jato. A reconstrução e o estudo de jatos têm sido usados para extrair mais informações do meio. Os elétrons foram selecionados pelo TPC (Time Projection Chamber, em inglês) e pelo EMCal (Electromagnetic Calorimeter, em inglês). O método de massa invariante foi utilizado para excluir elétrons não provenientes do decaimento de quarks pesados. Os jatos foram reconstruídos com o auxílio das bibliotecas do Fastjet, algorítmo anti kT e R = 0.4. A seleção de pares HFe-jato pode permitir uma melhor compreensão das propriedades do QGP e de sua interação com quarks pesados. Foram obtidos, para pp e p-Pb, os espectros de momento pT,chjet do jato, em dois intervalos de distância angular entre o elétron e o jato: regiões em oposição (away) e colinear (near). Também foi obtida a distribuição da distância angular para diferentes intervalos de momento peT do elétron. Os resultados para pp e p-Pb foram comparados através de dois observáveis: um em função do momento pT,chjet do jato, e outro em função do momento peT do elétron. O primeiro consistiu na razão dos espectros de momento pT,chjet do jato em pp e em p-Pb. O segundo, na razão do valores obtidos em pp e em p-Pb das áreas dos picos de cada uma das duas regiões de . Em ambos os casos, os valores das razões são compatíveis com a unidade, o que indica que a inexistência de efeitos extras em p-Pb em relação a pp.This thesis presents the first measurement of the distribution of jets that are correlated to heavy-flavour decay electron (HFe), reconstructed and identified with ALICE (A Large Ion Collider Experiment). The observables were measured in pp collisions at center of mass energy s = 8 TeV and in p-Pb at sNN = 5.02 TeV at the Large Hadron Collider (LHC). Exploring the heavy quarks created in relativistic heavy ion collisions is a powerful approach to study the new formed medium, known as Quark Gluon Plasma (QGP). This is due to the fact that they are created in the beginning of the collision, via hard scattering, and interact with the QGP throughout its whole existence. These quarks fragment into mesons that can decay (via the semi-electronic channel) into electrons (and positrons). These leptons can be used to identify the creation of a heavy quarks and allow QGP studies. The hard scattering, fragmenting and decaying processes originate several particles that are collimated in a conical region, and they can be grouped in what is called jet. The reconstruction and study of jets has been used to retrieve more information about the QGP and it is also a useful probe. The selected electrons were identified by the Time Projection Chamber (TPC) and the Electromagnetic Calorimeter (EMCal). Heavy-flavour decay electrons were selected via invariant mass method. The jets were reconstructed by the Fastjet framework, with the algorithm anti kT and R = 0.4. The HFe-jet pairs selection may allow a better comprehension of the QGP properties and its interactions with the heavy quarks. A jet pT,chjet spectrum was obtained, for pp and p-Pb, in two intervals of angular distance between the jet and the electron: away and near sides. The angular distance distribution was also obtained in different electron peT intervals. The results for pp and p-Pb were compared through two observables: the first one as a function of the jet pT,chjet, and the second, as a function of electron peT. The former consists in calculating the ratio of the jet pT,chjet spectra, in pp and in p-Pb. The latter, consists in calculating the ratio of the areas, in pp and in p-Pb, of each peak in the distribution. Both were compatible with the unity, which indicates that there is no extra effect in p-Pb with respect to pp.
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Harko, Tiberiu. "Properties of strange stars." Thesis, Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23242280.
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Boudinov, Edouard. "Measurement of the strange quark forward-backward asymmetry around the Z0 peak." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/83185.
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