Thèses sur le sujet « Gluons »
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Franzon, Bruno Cezar de Souza. « Gluons em estrelas de nêutrons ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-02082012-131729/.
Texte intégralThe Quark Gluon Plasma (QGP) at zero temperature and high baryon number is a system that may exist in the core of dense stars. This cold QGP has a rich phase structure and at high enough chemical potential it is quite possible that it shares some features with the hot QGP observed in heavy ion collisions, being also a strongly interacting system. We use an equation of state derived from QCD and apply it to study of stellar structure. Our results reproduce the measured mass, (1.97 ± 0.04)M, of the pulsar PSR J1614 2230.
Angeles, Martinez Rene. « Coulomb gluons and the ordering variable ». Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/coulomb-gluons-and-the-ordering-variable(c9d90246-4afa-4647-aece-bdd9605b7692).html.
Texte intégralWormsbecher, Wadim. « On Relations between Gluons and Gravitons ». Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20658.
Texte intégralWe analyze several cases of mysterious connections between gauge and gravity theories, known as double copy relations. We focus on tree level scattering amplitudes in Einstein-(scalar-)-chromo-dynamics, i.e. scattering scenarios between gluons, massive fundamental quarks (scalars) and gravitons. In these scenarios we study the sub leading contribution to the adjacent collinear gluon limits in pure Yang-Mills amplitudes. Recently, S. Stieberger and T. Taylor have proposed a linear combination of amplitudes with a pair of collinear gluons to an Einstein-Yang-Mills amplitude. We present a proof of such relations using a novel representation of bosonic tree level amplitudes based on a localized integral on the Riemann sphere, called the Cachazo-He-Yuan formalism. Moreover, we give insight into an intriguing interplay between those relations and surprising gauge invariance violations of the sub-leading collinear gluon limit of Yang-Mills amplitudes. Next, we will focus on yet another set of relations between Yang-Mills amplitudes and Einstein-Yang-Mills amplitudes that were also proposed by S. Stieberger and T. Taylor. They directly relate single gluons to single gravitons. We show universality of such relations, i.e. their validity in the presence of massive fundamental quarks and scalars. For that purpose, we will use a Feynman diagrammatic approach which results in a novel color-to-kinematics rule, mapping gluons to gravitons in these scattering scenarios. Finally, we establish a novel double copy connection between classical effective actions of two massive classical worldlines which are colored and interacting in Yang-Mills theory and dilaton charged and interacting through dilaton-gravity. Doing so, we extend and improve existing work relating the same system of worldlines through a double copy at the level of perturbative solutions to the involved equations of motion for the gluon and graviton fields, as has been proposed by W. Goldberger and A. Ridgway.
Cazaroto, Erike Roberto. « A saturação de gluons em futuros aceleradores ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-12032013-132708/.
Texte intégralIn this thesis we make predictions for the behavior of observables that will be measured in future particle colliders and also at the LHC. We address three different types of collisions: electron-ion (eA), photon-photon and proton-nucleus (pA). For eA processes we calculate the vector meson and real photon production cross section using the saturation models rcBK and b-CGC. We observe that only the production of heavy mesons will be useful to determine which saturation model correctly describes the dipole-proton interaction. For the photon-photon process we calculate the total cross section as well as the photon structure function. We propose a new saturation model for the interaction between two color dipoles and we compare its predictions with those of other models available in the literature. We observe that our model predicts a much smoother growth of the observables than the other models. As for pA collisions, we calculate the cross section of charm and bottom production at LHC energies. We observe that charm production is very sensitive to saturation effects as well as to nuclear shadowing effects. Therefore, this observable can be useful to determine the dynamics of QCD at high energies, as well as the magnitude of the shadowing. On the other hand, only the bottom production cross section is sensitive to antishadowing effect.
Isert, Dagmar Sigrun. « Transport theory for scalar quarks and gluons ». [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961877200.
Texte intégralKubelskyi, Oleksandr. « Gluons and the spin of the proton ». Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-125564.
Texte intégralSilva, Paulo Sérgio Rodrigues da [UNESP]. « Conseqüências fenomenológicas de um propagador de gluons com massa dinâmica ». Universidade Estadual Paulista (UNESP), 1998. http://hdl.handle.net/11449/102520.
Texte intégralSão analisados as consequências de um comportamento finito no infravermelho para certos propagadores de gluons discutidos na literatura. Três problemas distintos são estudados: o cálculo da constante de acoplamento crítico que leva à transição quiral à comparação entre as fenomelogias do Pomeron e de quebra dinâmica de simetria quiral e o cálculo do potencial efetivo para operadores compostos na QCD puramente gluônica. Os resultados obtidos mostram como dados fenomenológicos podem auxiliar a mapear o comportamento do propagador do gluon na região infravermelha.
Abstracts: The consequences of an infrared finite behavior of some gluon propagators are examined. Three distint problems are studied: the computation of the critical coupling constant which leads to chiral transition the confrontation between the Pomeron and dynamical chiral symmetry breawing phenomenologies and the calculation of the efective potential for composite operators in the purel gluonic QCD. The results show how phenomenological data can aid to trace the gluon propagator behavior in the infrared.
Silva, Paulo Sérgio Rodrigues da. « Conseqüências fenomenológicas de um propagador de gluons com massa dinâmica / ». São Paulo : [s.n.], 1998. http://hdl.handle.net/11449/102520.
Texte intégralResumo: São analisados as consequências de um comportamento finito no infravermelho para certos propagadores de gluons discutidos na literatura. Três problemas distintos são estudados: o cálculo da constante de acoplamento crítico que leva à transição quiral à comparação entre as fenomelogias do Pomeron e de quebra dinâmica de simetria quiral e o cálculo do potencial efetivo para operadores compostos na QCD puramente gluônica. Os resultados obtidos mostram como dados fenomenológicos podem auxiliar a mapear o comportamento do propagador do gluon na região infravermelha.
Abstracts: The consequences of an infrared finite behavior of some gluon propagators are examined. Three distint problems are studied: the computation of the critical coupling constant which leads to chiral transition the confrontation between the Pomeron and dynamical chiral symmetry breawing phenomenologies and the calculation of the efective potential for composite operators in the purel gluonic QCD. The results show how phenomenological data can aid to trace the gluon propagator behavior in the infrared.
Doutor
Ziaeepour, Houri. « Contribution a l'étude des possibilités de mesurer les fonctions de structures à HERA avec H1 ». Paris 7, 1989. http://www.theses.fr/1989PA077127.
Texte intégralRoy, 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.
Texte intégralAprès 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.
Andrieux, Vincent. « Polarisation of quarks and gluons inside the nucleon ». Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112244/document.
Texte intégralThe 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%
Basa, Stéphane. « Recherche des gluinos et des squarks dans le cadre du modèle supersymétrique minimal au LHC : étude des performances d'un prototype de calorimètre électromagnétique plomb/fibres scintillantes ». Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX22026.
Texte intégralScarpa, Florent. « Probing the gluon Transverse Momentum-Dependent distributions inside the proton through quarkonium-pair production at the LHC ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS104.
Texte intégralTransverse momentum-dependent factorisation is used to describe hadronic collisions while taking into account the intrinsic transverse momentum of partons inside hadrons. This requires the use of Transverse Momentum-Dependent Parton Distribution Functions (TMDPDFs or simply TMDs) in order to parametrise the parton correlator. Such distributions need to be extracted from experimental data. Quark TMDs are relatively well known thanks to processes such as semi-inclusive deep inelastic scattering (SIDIS) and Drell-Yan for which numerous data exist. Gluon TMDs remain poorly known, since there is no ideal process to probe them in the operating colliders. The future Electron-Ion Collider (EIC) will offer a much better access to them, but its first run remains at least 10 years from now. It is also important to study TMDs in various kinds of processes in order to check their universality which is not as trivial as that of collinear PDFs.We propose to use quarkonium-pair production to study the two leading-twist gluon TMDs accessible through unpolarised proton collisions at the Large Hadron Collider (LHC). Quarkonia are mesons, i.e. bound states of a quark-antiquark pair. In the case of a quarkonium, the pair is made of heavy flavours: charmonia combine a charm with an anticharm, while bottomonia combine a bottom with an antibottom. J/psi mesons are the lowest lying vector state of charmonia and are produced in large amounts at the LHC. J/psi pairs originate from gluon fusion in vast majority, which is important in order to focus on gluon TMDs. Studying two-particle final states also allows one to tune the hard scale of the process commensurate to the pair mass, which in turn allows one to study TMD evolution.We first use a model of Gaussian-based TMDs to compute observables in J/psi-pair production that are sensitive to the TMDs. These observables are the transverse-momentum spectrum of the pair, mostly sensitive to the unpolarised gluon TMD, and azimuthal asymmetries, whose existence requires the linearly-polarised gluon TMD. We see that J/psi pair production is an ideal process to probe the linearly-polarised gluon distribution through one azimuthal asymmetry that is maximal at large hard scales. We also use the LHCb data on the J/psi pair transverse momentum to fit the average gluon transverse momentum using our Gaussian-based model. The large value that is obtained is interpreted as a consequence of TMD evolution that perturbatively enhances the intrinsic transverse momentum of the gluon at such large hard scales.We then improve our predictions by including TMD evolution in the formalism used to describe the gluon TMDs in our calculations. In this picture, the unpolarised gluon distribution is a leading contribution in an expansion of the strong coupling, while the linearly-polarised distribution is subleading. The remaining nonperturbative component is modelled using a Gaussian. We observe that the computed magnitude of the azimuthal asymmetries in J/psi-pair production are lower than when using the purely Gaussian model. However, we observe that these asymmetries remain sizeable and could be detected at the LHC. We also provide predictions for Upsilon-pair production (the Upsilon is the bottomonium equivalent of the J/psi).We finally study the helicity structure of the quarkonium-pair production amplitude. It can be written as a sum of sub-amplitudes corresponding to various helicity states of the initial-state gluons and final-state quarkonia. In the high-mass limit of the pair, the amplitudes greatly simplify and explain how the hard-scattering coefficients of J/psi-pair production maximise the size of one azimuthal asymmetry, as previously observed. Moreover, it is shown that the amplitude zero for longitudinally polarised pairs predicted at leading order in the collinear regime exists as well in TMD factorisation. It should survive for intermediate masses as hard gluon emissions are suppressed in the TMD regime
Murphy, Kevin Christoher Klink William H. « The structure of gluons in point form quantum chromodynamics ». [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/411.
Texte intégralIdilbi, Ahmad S. « QCD resummation of soft gluons in effective field theory ». College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3317.
Texte intégralThesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Murphy, Kevin Christoher. « The structure of gluons in point form quantum chromodynamics ». Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/411.
Texte intégralReis, Arthur Luciano Vezzoni Ramos dos. « \"Saturação de gluons e perda de energia em colisões hadrônicas\" ». Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-10042007-142304/.
Texte intégralIn this work we use the Interacting Gluon Model (IGM), a model that describes quite well the energy flow in hadronic collisions, to study the leading particle spectrum when gluon saturation effects are included. The leading particle spectrum is calculated for several center of mass energies (s^1/2), using gluon distribution functions with and without saturation effects. In both cases the resulting spectrum becomes softer for increasing energies. With saturation the softening is less pronounced than without.
Yamamoto, Arata. « Lattice QCD Anatomy via the Energy-Momentum Component of Gluons ». 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142379.
Texte intégralWong, Stephen Man Hoe. « Finite temperature field theory - hard thermal loops and the quark-gluon plasma ». Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309328.
Texte intégralPonte, Mickel Abreu de [UNESP]. « Cálculo da auto-energia de um quark num modelo de QCD com glúons confinantes ». Universidade Estadual Paulista (UNESP), 2000. http://hdl.handle.net/11449/132668.
Texte intégralMihara, Antonio [UNESP]. « A fenomenologia hadrônica e as soluções das equações de Schwinger-Dyson ». Universidade Estadual Paulista (UNESP), 2003. http://hdl.handle.net/11449/132818.
Texte intégralAguilar, Arlene Cristina. « Geração de massa em Teorias de Gauge / ». São Paulo : [s.n.], 2004. http://hdl.handle.net/11449/102511.
Texte intégralBanca: Attílio Cuchieri
Banca: Gastão Inácio Krein
Banca: Marcelo Otávio Caminha Gomes
Banca: Adilson José da Silva
Resumo: O sistema complexo de equações de Schwinger-Dyson nos fornece uma abordagem não perturbativa na qual as propriedades infravermelhas da QCD, tais como comportamento de propagadores e vértices podem ser estudados. Utilizando essas equações, o comportamento do propagador do gluon é estudado, no gauge de Landau, do regime perturbativo ao não-perturbativo. Entretanto para fazer essa torre de equações tratável, algumas aproximações são necessárias. Aqui nós vamos discutir dois esquemas diferentes que foram aplicados na equação de Schwinger-Dyson: a aproximação de Mandelstam e o sistema acoplado gluon-ghost. A primeira aproximação consiste em desprezar todas as contribuições que vêem dos campos de férmions e ghosts, enquanto que na segunda aproximação, os campos de ghosts são levados em conta, nos levando a um sistema de equações integrais acopladas. Em ambos os casos, nós mostraremos que uma massa dinâmica para o gluon surge como solução, e algumas de suas propriedades, tais como sua dependência com a escala da QCD, 'lâmbda IND.QCD', e seu comportamento perturbativo serão discutidos.
Abstract: The complex system of Schwinger-Dyson equations (SDE) provides a non-perturbative framework in which we can study the infrared properties of QCD such as propagators and vertex. Using SDE, the behavior of gluon propagator is studied in Landau Gauge from perturbative to non-perturbative regimes. However to make this tower of equations tractable some approximations are needed. Here we discuss two different schemes which were applied for the SDE: the Mandelstam and gluon-ghost approximaions. The former consist in neglecting all contributions that come from fermions and ghosts fields while in the latter, the ghosts field are taken into account which lead to a coupled system of integral equations. In both cases, we show that a dynamical mass for the gluon propagator arises as a solution, and some of its properties, such as its dependency on 'lâmbda IND.QCD' and how is its behavior at large momenta, will also be discussed.
Doutor
Ponte, Mickel Abreu de. « Cálculo da auto-energia de um quark num modelo de QCD com glúons confinantes / ». São Paulo : [s.n.], 2000. http://hdl.handle.net/11449/132668.
Texte intégralRenaud, Adrien. « Recherche de gluons scalaires avec le détecteur ATLAS auprès du LHC ». Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00934510.
Texte intégralIracane, Daniel. « Etude des condensats de gluons au moyen d'une transformation de bogoliubov ». Paris 11, 1985. http://www.theses.fr/1985PA112162.
Texte intégralWe describe the ground state of non-perturbative QCD as a gluon condensate. In the framework of the Coulomb gauge hamiltonian, we introduce an effective interaction between infrared gluons by removing high-momentum gluons. The Bogoliubov transformation provides us with our variational space. The minimisation over this Fock subspace leads to a non-perturbative vacuum and its excitations. The minimum functional space for a boson dynamic is a distribution set. We find two kinds of condensation. The first one occurs only for zero-momentum states and looks like the Bose Condensation. In the second one, the quasiparticle spectrum shows a finite gap and the vacuum is a supraconducting state. We give constraints on the interaction so that the supraconducting phase is more bounded than the Bose one
Boüard, Gilles de. « Recherche des électrons directs dans l'expérience de photoproduction Na14 au CERN ». Paris 11, 1985. http://www.theses.fr/1985PA112068.
Texte intégralThe purpose of this thesis is to isolate a prompt electron signal from the data of the NAl4 photoproduction experiment at CERN. For that aim, a fast data filtering program has been developed. In order to have a good understanding of the electrons behaviour in the electromagnetic calorimeter, electrons from photon conversion were selected. The observation of events with a reconstructed ψ and the sharing between the different ψ production mechanism leads to a clear excess of the inelastic process relative to a QCD theoretical expectation. The prompt electrons measurement method, when applied to events obtained from a π⁻ beam, does not give any evidence for a signal. With incident photons, a strong signal is seen which cannot be explained by the Bethe Heitler mechanism and production alone. This signal is stronger than the photon-gluon fusion model prediction
Mebarki, Noureddine. « Problems of higher order corrections in perturbative QCD and supersymmetric QCD ». Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74057.
Texte intégralJackson, Greg. « The Runny Gauge Plasma : shear viscosity to entropy for quarks and gluons ». Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/23061.
Texte intégralBernet, Colin. « Caractérisation des micromégas et mesure de la polarisation des gluons sur COMPASS ». Paris 7, 2004. http://www.theses.fr/2004PA077205.
Texte intégralDurães, Francisco de Oliveira. « Estudo do Fluxo de Energia em Colisões Hadrônicas e em Fotoprodução a Altas Energias ». Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-18062012-155856/.
Texte intégralWe present and apply to several situations a model for particle production. With this model it is possible to understand the energy flow in hadronic reactíons, in photoproduction and also ma.ke predictions for the behaviour of some observables at higher energies. It is also possible to study the individual contributions of soft and semíhard interactions and the individual contributions coming from the central and fragmentation regions. We analyse charged and charmed particle production data at several energies. We predíct, among other things, that an increasing fraction of the reaction energy is going to be released in the central region. As a consequence the asymmetry observed in charm production will decrease. We study and propose as experimental test to heavy meson production from light quark fragmentation.
Filho, Elienos Pereira de Oliveira. « Study of the angular correlation between heavy-flavour decay electrons and charged unidentified particles in pp and p-Pb collisions with ALICE ». Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-18012015-125411/.
Texte intégralO próposito de colisões entre íons pesados relativísticos é investigar as propriedades do plasma de quarks e gluons (QGP, do inglês Quark-Gluon Plasma). A transição de fase, de um estado hadrônico para o QGP, ocorre em regimes onde a temperatura e/ou densidade atingem um valor suficientemente alto. Neste contexto, colisões entre íons pesados e leves (por exemplo, p-Pb) permitem acessar efeitos devido à matéria nuclear fria (CNM, do inglês Cold Nuclear Matter) e colisões elementares (por exemplo, próton-próton) são usadas como referência para estudos com íons pesados, além de proporcionarem testes para cálculos de QCD perturbativa. Quarks pesados, isto é charm e bottom, são ferramentes muito convenientes no estudo e caracterização do QGP. Essas partículas são produzidas através de espalhamento duro nos instantes iniciais da colisão e, portanto, elas atuam como uma sonda externa para o sistema criado na reação. Esse trabalho consiste no estudo da correlação angular entre elétrons oriundos de quarks pesados e partículas carregadas, em colisões pp (2.76 e 7 TeV) e p-Pb (5.02 TeV), no acelerador LHC (do inglês Large Hadron Collider) do CERN, usando o detector ALICE (do inglês A Large Ion Collider Experiment). A distribuição angular mencionada foi medida em função da multiplicidade do evento, no caso de colisões p-Pb. Em colisões pp, a contribuição relativa de quarks charm e bottom para o total de elétrons provenientes de quarks pesados foi estimada usando a função de correlação obtida.
Perantonis, S. J. « Model calculations in quantum chromodynamics and other field theories ». Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379929.
Texte intégralFong, Che Ping. « Jet fragmentation at small momentum fractions in quantum chromodynamics ». Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239209.
Texte intégralMachado, Fátima Araujo. « Dynamical gluon masses in perturbative calculations at loop level : towards an effective loop expansion for quantum chromodynamics / ». São Paulo, 2014. http://hdl.handle.net/11449/154726.
Texte intégralBanca: Gastão Krein
Banca: Eduardo Fraga
Banca: Letícia Palhares
Banca: Marcelo Guimarães
Resumo: A presente tese é baseada em parte do trabalho realizado durante o Doutorado e diz respeito aos dois domínios da Cromodinâmica Quântica (QCD) a temperatura zero: o regime confinado, a baixas energias, e o assintoticamente livre, a altas energias. Com o objetivo de cumprir uma ponte entre estes domínios e inspirado em sugestões de aprimoramentos da série perturbativa, este trabalho investiga uma proposta para uma expansão perturbativa aprimorada, a ser um método aplicável tanto à fenomenologia da QCD quanto a estudos de seu regime não-perturbativo. A proposta consiste numa expansão em loops efetivos - um híıbrido entre equações de Schwinger-Dyson e expansão em loops usual, fazendo uso de ferramentas desta porém vestindo certas quantidades como forma de considerar seu comportamento completo dentro de loops. A tese descreve os principais avanços nesse sentido, na aplicação a funções de correlação - em particular os propagadores do gluon e do ghost, como um passo preliminar a futuras aplicações. Após lidar com questões de transversalidade do propagador do gluon e renormalizabilidade no método, a expansão em loops efetivos na sua presente forma contém gluons (dinamicamente) massivos e uma carga efetiva, além da possiblidade de uma vestimenta para o vértice de três gluons. Nesta formulação, foram obtidos resultados qualitativos razoáveis para o comportamento não-perturbativo completo dos propagadores do ghost e do gluon, e comparação com a rede é analisada. Perspectivas de curto e de mais longo prazo são discutidas
Abstract: This thesis is based on part of the work done during the Ph.D., and it concerns the two distinguished domains of Quantum Chromodynamics (QCD) at zero temperature: the low-energy, confined domain, and the high-energy, asymptotically free one. Aiming to bridge the gap between them, and inspired by suggested improvements of the QCD perturbative series, this work investigates a proposal for an improved perturbative expansion, as a method to be applicable to QCD phenomenology, as well as to nonperturbative studies. The proposal consists in an effective-loop expansion - a hybrid between Schwinger- Dyson equations and usual loop expansions, making use of the latter's framework, yet dressing certain quantities in order to account for their complete behavior inside loops. The thesis describes the main efforts on this matter, in its application to correlation functions - the gluon and ghost propagators, in particular, as a preliminary step preceding further applications. After dealing with issues as transversality of the gluon self-energy and renormalizability within the method, the present form of the effective-loop expansion contains dynamically massive gluons and an effective running charge, besides the possible dressing of the three-gluon vertex. Within this formulation, reasonable qualitative results were obtained for achieving the complete, nonperturbative behavior of the ghost and gluon propagators, and comparison with lattice is analyzed. Readily achievable and longer term prospects are also discussed
Doutor
Machado, Fátima Araujo [UNESP]. « Dynamical gluon masses in perturbative calculations at loop level : towards an effective loop expansion for quantum chromodynamics ». Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/154726.
Texte intégralFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A presente tese é baseada em parte do trabalho realizado durante o Doutorado e diz respeito aos dois domínios da Cromodinâmica Quântica (QCD) a temperatura zero: o regime confinado, a baixas energias, e o assintoticamente livre, a altas energias. Com o objetivo de cumprir uma ponte entre estes domínios e inspirado em sugestões de aprimoramentos da série perturbativa, este trabalho investiga uma proposta para uma expansão perturbativa aprimorada, a ser um método aplicável tanto à fenomenologia da QCD quanto a estudos de seu regime não-perturbativo. A proposta consiste numa expansão em loops efetivos - um híıbrido entre equações de Schwinger-Dyson e expansão em loops usual, fazendo uso de ferramentas desta porém vestindo certas quantidades como forma de considerar seu comportamento completo dentro de loops. A tese descreve os principais avanços nesse sentido, na aplicação a funções de correlação - em particular os propagadores do gluon e do ghost, como um passo preliminar a futuras aplicações. Após lidar com questões de transversalidade do propagador do gluon e renormalizabilidade no método, a expansão em loops efetivos na sua presente forma contém gluons (dinamicamente) massivos e uma carga efetiva, além da possiblidade de uma vestimenta para o vértice de três gluons. Nesta formulação, foram obtidos resultados qualitativos razoáveis para o comportamento não-perturbativo completo dos propagadores do ghost e do gluon, e comparação com a rede é analisada. Perspectivas de curto e de mais longo prazo são discutidas
This thesis is based on part of the work done during the Ph.D., and it concerns the two distinguished domains of Quantum Chromodynamics (QCD) at zero temperature: the low-energy, confined domain, and the high-energy, asymptotically free one. Aiming to bridge the gap between them, and inspired by suggested improvements of the QCD perturbative series, this work investigates a proposal for an improved perturbative expansion, as a method to be applicable to QCD phenomenology, as well as to nonperturbative studies. The proposal consists in an effective-loop expansion - a hybrid between Schwinger- Dyson equations and usual loop expansions, making use of the latter's framework, yet dressing certain quantities in order to account for their complete behavior inside loops. The thesis describes the main efforts on this matter, in its application to correlation functions - the gluon and ghost propagators, in particular, as a preliminary step preceding further applications. After dealing with issues as transversality of the gluon self-energy and renormalizability within the method, the present form of the effective-loop expansion contains dynamically massive gluons and an effective running charge, besides the possible dressing of the three-gluon vertex. Within this formulation, reasonable qualitative results were obtained for achieving the complete, nonperturbative behavior of the ghost and gluon propagators, and comparison with lattice is analyzed. Readily achievable and longer term prospects are also discussed
FAPESP: 2011/10889-0
Tram, Vi-Nham. « Etude de la production du J/v dans les collisions or-or à 200GeV par paire de nucléons dans l'expérience PHENIX ». Palaiseau, Ecole polytechnique, 2006. https://pastel.archives-ouvertes.fr/pastel-00001917.
Texte intégralD'Agostini, Gilles. « Etude des propriétés et des effets du gluon dans la diffusion très inélastique d'un muon sur un nucléon ». Aix-Marseille 2, 1986. http://www.theses.fr/1986AIX22050.
Texte intégralWelzbacher, Christian Andreas [Verfasser]. « Quarks and gluons in the phase diagram of quantum chromodynamics / Christian Andreas Welzbacher ». Gießen : Universitätsbibliothek, 2016. http://d-nb.info/1112909974/34.
Texte intégralGirard, Cyrille. « Étude de la saturation de gluons dans le cadre du groupe de renormalisatio ». Nantes, 2002. http://www.theses.fr/2002NANT2055.
Texte intégralChatagnon, Pierre. « Nucleon structure studies with CLAS12 at Jefferson Lab : timelike Compton scattering and the central neutron detector ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP039.
Texte intégralThe nucleons, protons and neutrons, are the main constituents of visible matter in the universe. Their structure, three valence quarks surrounded by a cloud of sea quarks and gluons, is described by the theory of quantum chromodynamics (QCD). However, the properties of QCD cannot be computed perturbatively at energies comparable to the nucleon mass. Hence, structure functions were adopted to model the inner structure of nucleons. The Generalized Partons Distributions (GPD), were introduced in the 90's to provide a description of the nucleon in terms of both the transverse position and the longitudinal momentum of its quarks and gluons. These functions contain a large amount of information and are closely related to the nucleon spin and mechanical architecture. Their experimental measurement is a key element for the understanding of fundamental properties of matter. The main focus of this thesis is to provide new data for GPD studies, with a first-time measurement of Timelike Compton Scattering at Jefferson Lab with the CLAS12 detector.This thesis is divided in three parts. The first part presents the theory of GPDs, current models and their link with physical processes that can be experimentally measured. The relation between GPDs and experimental observables is discussed, and the concept of Compton Form Factors (CFF) is introduced. In addition, the link between the spin and the mechanical properties of the nucleon, as well as the possibility of performing a 3D imaging of the nucleon with GPDs is highlighted.The second part of the manuscript is dedicated to the work I performed on the Central Neutron Detector (CND). The CND is a plastic scintillator barrel built to increase the neutron detection capabilities of CLAS12 in its central region. After presenting the physical motivations for the building of this detector, its hardware implementation, calibration, reconstructions and simulation aspects are detailed. At the end of this part, the CND performances using real data are measured and compared to its design specifications.Finally, the third part covers the experimental measurement of the photo-production of a lepton pair off the proton, the Timelike Compton Scattering process (TCS). This reaction offers an insight on some properties of GPDs which are not well constrained by the reactions measured so far, in particular the real part of CFFs. The experimental setup used for data taking is described. The subsequent data processing and analysis is explained, and results for three different observables are shown
Bonnet, Frédéric D. R. « Improved actions in lattice QCD / ». Title page, contents and introduction only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phb717.pdf.
Texte intégralRobinet, Florent. « Mesure de la polarisation des gluons dans le nucléon par la muo-production de mésons charmés à COMPASS ». Paris 7, 2008. http://www.theses.fr/2008PA077138.
Texte intégralThe 1/2 spin of the nucleon decomposes into three contributions : the quark and the gluon spin and their angular momenta. It is known that the fraction of the nucleon spin carried by the quarks is small. Nowadays, a series of measurements aims to determine the contribution of the gluon spin in order, perhaps, to recover the totality of the nucleon spin. This is one of the main goals of the COMPASS experiment at CERN where spin asymmetries are measured using a polarized nucleon beam on a polarized nucleon target. The photon-gluon fusion processes, sensitive to the gluon polarization, are selected by detecting D° in the final state. This method offers a very clean selection of the desired signal but is statistically limited. The work presented in this thesis is primarily focused on the development of an analysis method maximizing the statistics. In particular, the D° mesons reconstruction is submitted to a high combinatorial background. Parameterizing the probability for an event to be signal, the statistical error is significantly reduced. The momentum resolution, associated with the particule detection, is an important factor allowing to minimize the combinatorial background. This thesis presents the characteristics of drift chamber-type detectors contributing to the performances of the COMPASS spectrometer. Finally, the results, joined by the systematic errors study, are presented along with their implications on the contribution of the gluon spin to the nucleon spin
Li, Xiaomei. « Identification des photons dans les collisions d'ions lourds ultra relativistes ». Nantes, 2002. http://www.theses.fr/2002NANT2042.
Texte intégralGuiot, Benjamin. « Production de charms et de photons prompts avec le générateur d'évènements EPOS ». Thesis, Nantes, Ecole des Mines, 2014. http://www.theses.fr/2014EMNA0192/document.
Texte intégralAt the LHC, strong interaction is studied by doing collisions of high energy particles. In the case of nucleus-nucleus collision (lead at the LHC), a new state of matter, called Quarks Gluons Plasma (QGP), is created. The study of this QGP is currently a lively research field. Hard probes, like heavy quarks and prompt photons, are produced during early times of collisions done at the LHC. This is why they are ideal probes for the study of the QGP. They will go through and interact with the medium produced by the collision. A comparison with a case without QGP (proton-proton- collision) will allow us to see how hard probes properties are modified by themedium. Then, medium properties like temperature and density can be extracted. This study requires a good understanding of hard probes production in proton-proton collisions. The aim of my thesis is the implementation of heavy quarks and prompt photons in the event generator EPOS (computer code for colliders), for p-p collisions. Our final aim is the study of the QGP in Pb-Pb collisions
Souza, Maria Simone Kugeratski. « Dipolos de cor e interações a altas energias ». Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17122007-095340/.
Texte intégralAt high energies a nucleus (and even a nucleon) becomes a dense gluonic system called the color glass condensate. In this work we study the interaction of this dense system with color dipoles. This interaction is represented by the dipole-target cross section, which has to be modeled. We have used, without success, some of the existing models to try to reproduce the data obtained at HERA and RHIC. It was not possible to obtain a global agreement between the models and the two sets of data. We have then proposed a different parametrization of the dipole cross section, which is now compatible with all the available data. In the case of deep inelastic scattering, we have extended the Iancu-Itakura-Munier model to nuclear targets and made predictions for observables to be measured in the future electron-ion collider eRHIC. Among other things, we have concluded that a large fraction of the events will be of the diffractive type. Finally, we have used the color dipole approach to build a simple model for the charmonium-hadron interaction at high energies.
Wormsbecher, Wadim [Verfasser], Jan [Gutachter] Plefka, Dirk [Gutachter] Kreimer et Donal [Gutachter] O'Connell. « On Relations between Gluons and Gravitons / Wadim Wormsbecher ; Gutachter : Jan Plefka, Dirk Kreimer, Donal O'Connell ». Berlin : Humboldt-Universität zu Berlin, 2019. http://d-nb.info/1199340103/34.
Texte intégralMihara, Antonio. « A fenomenologia hadrônica e as soluções das equações de Schwinger-Dyson / ». São Paulo, 2003. http://hdl.handle.net/11449/132818.
Texte intégralBanca: Atílio Cucchieri
Banca: Márcio José Menon
Banca: Maria Beatriz de Leone Gay Ducati
Banca: Rogério Rosenfeld
Resumo: Através da solução das equações de Schwinger-Dyson (ESD) é possível estudar diversos aspectos importantes da QCD não-perturbativa como confinamento e quebra de simetria quiral; desta forma as ESD são, obviamente, muito interessantes para estudo da fenomenologia das interações hadrônicas. Após uma breve revisão sobre equações de Schwinger-Dyson (ESD) e sobre algumas soluções da ESD do propagador do glúon disponíveis na literatura, apresentamos possíveis testes fenomenológicos para estas soluções. Observaremos que apenas uma das soluções apresentadas descreve satisfatoriamente os dados experimentais, e esta solução é compatível com uma massa dinâmica para o glúon. Finalizando, supomos que o glúon têm uma massa dinâmica e calculamos seus efeitos sobre os decaimentos de quarkônios pesados
Abstract: Through the solution of Schwinger-Dyson equations (SDE) it is possible to study important features of nonperturbative QCD such as confinement and chiral symmetry breaking; in this way SDE are, obviously, very interesting for the study of phenomenology of hadronic interactions. After a brief review on SDE and some Solutions of gluon propagator SDE available in literature, we present possible phenomenological tests for these solutions. We shall observe that only one of the solutions presented describes satisfactorily the experimental data, and such solution is compatible with a dynamical mass for the gluon. Eventually, we assume that the gluon has a dynamical mass and calculate its effects on heavy quarkonia decays
Doutor
Gardim, Fernando Gonçalves. « Seções de choque totais hadrônicas e colisões entre partons / ». São Paulo, 2005. http://hdl.handle.net/11449/132597.
Texte intégralBanca: Juan Carlos Montero Garcia
Banca: Márcio José Menon
Resumo: Discutiremos alguns modelos fenomenológicos baseados na QCD perturbativa que tentam descreve a seção de choque total hadrônica. Falaremos sobre as principais características dos espalhamentos hadrônicos, como o crescimento da seção de choque total com a energia devido ao aumento no número de jatos, e o decrescimento da seção de choque total a baixas energias. Mostraremos a inviabilidade do tratamento perturbativo de QCD para o cálculo da seção de choque total hadrônica. Estudaremos alguns espalhamentos hadrônicos no limite de baixas energias utilizando informações não-perturbativas das propriedades do sistema, tal como o fato do gluon adquirir massa dinâmica nesta região. Averiguando propriedades e modelos que procuram descrever a seção de choque total hadrônica, obteremos idéias suficientes para propor um modelo que descreva a seção de choque total hadrônica real
Abstract: We discuss some phenomenological models based on perturbative QCD, that try to describe the total hadronic cross section. We comment on peculiarities of hadronic scattering, as the increase of cross section at high energies, as well as its decrease in low energies. Some of the problems of perturbative QCD to deal with the total cross section calculation are discussed. We discuss how non-perturbative QCD properties, as the generation of a dynamical gluon mass, can be introduced in the low energy limit of the total cross section calculation. Finally we propose a phenomenological way to modify the total hadronic cross section calculation with these non-perturbative information
Mestre
Taurines, Andre Ribeiro. « Comportamento infravermelho do propagador do glúon na rede ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2003. http://hdl.handle.net/10183/4919.
Texte intégralGuimarães, Karin Silvia Franzoni Fornazier. « Estudo da produção de estranheza em colisões entre íons pesados relativísticos a & ; ». Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17122007-105539/.
Texte intégralThe main goal of this work was to measure the production of the singly strange particles, such as K0, and in Au+Au collisions at ?sNN = 62.4 GeV, inserting these results in a systematic energy scan study. The data were obtained from the STAR detector, one of the RHIC experiments. In addition, we have used the particle production in these collision to study two specific stages of the fireball evolution: the chemical and kinetic freeze-outs. These two stages were studied comparing the ratio between different particles (strange or not) and also the transverse momentum distribution with thermal models fits in order to check possible effects of equilibrated Quark Gluon Plasma (QGP) in the hadron production. The chemical freeze-out was studied comparing the ratios between particles produced in the collision with two different thermal models: one which assumes a equilibrated hadron gas (THERMUS) and another one which assumes a possible non-equilibrated system (SHM). The experimental data were well described by the THERMUS model fit in a great range of energy collisions, mainly at 62.4 GeV. The thermodynamic parameters had been studied as function of the energy in order to verify if it has a smooth or abrupt behavior. The result indicated that this behavior is very smooth with energy. We also compared these results with SHM\'s predictions and, in this comparison, the ratio presented an interesting behavior, suggesting that at low energies the fireball consists of a non-equilibrated system, such as described by SHM model, whereas the model that considers the fireball as a equilibrated hadron gas. The kinetic freeze-out was studied with the transverse momentum spectra using a hydrodynamics inspired model. The results indicate that for the most central events there is a higher expanding velocity and a lower freeze-out temperature. It was also observed that for the particle, the freeze-out temperature is higher than the one for other particles (?, K, p) indicating an earlier decoupling of these particles from the fireball. Finally, we have studied the inclusion for the SVT in the V0 reconstruction analysis, trying to optimize this detector usage in the analysis. The results show that the inclusion of this detector in the analysis can improve the efficiency and purity of the V0 reconstruction in the STAR experiment.