Made available in DSpace on 2016-01-13T13:27:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-06. Added 1 bitstream(s) on 2016-01-13T13:31:35Z : No. of bitstreams: 1 000677106.pdf: 2599098 bytes, checksum: d9013a92ac254365852ffbd2bc1b8ced (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / In this thesis, we are dedicated to study the time evolution generated by the hamiltonian of a classical Yang-Mills-Higgs theory with gauge symmetry SU(2) on a spatial lattice. In particular, we study energy transfer and equilibration processes among the gauge and Higgs sectors, calculate the maximal Liapunov exponents regarding to random initial conditions in the regime of weak coupling, where one expects them to be related to the high-temperature static plasmon damping rate, and investigate their energy and Higgs self-coupling parameter dependence. We further examine finite-time and finite-size errors, value the impact of the Higgs fields on the instabilty of constant non-abelian magnetic fields and comment on the implications of our obtained results for the thermalization properties of gauge fields at finite temperature in the presence of matter.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Alguns aspectos não perturbativos das teorias de Yang-Mills puras em quatro dimensões Euclideanas, quantizadas no calibre de Landau, são estudados analiticamente. Por pura entendemos a teoria na ausência de matéria (férmions). Em particular, ivestigamos a geração dinâmica de massa para os gluons devido a presença de condensados de dimensão dois. Este estudo é feito utilizando a técnica de operadores locais compostos no caso da ação de Yang-Mills, bem como, no caso da ação de Gribov-Zwanziger. Além deste estudo, uma investigação sobre as ambigüidades de Gribov nos calibres lineares covariantes é apresentada. No caso da ação de Yang-Mills, fizemos uma análise detalhada da técnica de opera-dores locais compostos quando introduzidos, simultaneamente, os operadores A&#956;aA&#956;a e fabcc*bcc. Através da teoria da renormalização algébrica, provamos a renormalizabilidade do modelo a todas as ordens em teoria de perturbações. Com o auxílio das equações do grupo de renormalização uma ação quântica efetiva é construída para os condensados <A&#956;aA&#956;a> e <fabcc*bcc>. Esta construção é feita utilizando a regularização dimensional em conjunto com o esquema de renormalização MS. Mostramos que um valor não trivial para estes condensados é favorecido dinamicamente, independentemente da escala escolhida. Cálculos explícitos, a um laço, são apresentados fornecendo estimativas numéricas para estes condensados e para a energia do vácuo. Através de um estudo via identidades de Ward, somos capazes de mostrar formalmente que a presença do condensado Overhauser, <fabcc*bcc>, é responsável pela quebra de transversalidade da polarização do vácuo. Contudo, o propagador do glúon permanece transverso, a todas as ordens em teorias de perturbações. Finalmente, esta análise é terminada com o cálculo explícito da correção, a um laço, à massa do glúon, devido a presença destes condensados. O resultado é que existe uma quebra na degenerescência da massa entre gluons Abelianos e não Abelianos. Esta quebra, devido a massa não Abeliana ser maior que a Abeliana, pode ser interpretada como uma evidência da dominância Abeliana no calibre de Landau. Com relação à ação de Gribov-Zwanziger sem a inclusão de condensados, começamos por efetuar cálculos explícitos. Mostramos formalmente que, a um laço, a energia do vácuo será sempre positiva, independentemente do esquema de renormalização escolhido e da escala. Apresentamos uma discussão sobre a procura de soluções da condição de horizonte no esquema MS, a um e dois laços, e as respectivas dificuldades encontradas. Em seguida, mostramos, através da teoria de renormalização algébrica, que a inclusão do operador A&#956;aA&#956;a na ação de Gribov-Zwanziger via o formalismo LCO é renormalizável a todas as ordens em teoria de perturbações. Tentativas de resolver as equações de gap são apresentadas no esquema de renormalização MS a um laço. Mostramos formalmente que, para a condição de horizonte, não existem soluções para <A&#956;aA&#956;a> < 0 e somente uma solução para <A&#956;aA&#956;a> > 0 pode existir. Contudo, no esquema MS, não fomos capazes de encontrar esta solução explicitamente. Desta forma, uma aprimoração do esquema de renormalização é feita de forma a minimizar a dependência no esquema escolhido. Nesta otimização encontramos a solução no limite MS bem como para o caso em que a dependência no esquema de renormalização é mínima. Em ambos os casos, a energia do vácuo se mostra positiva e o condensado <A&#956;aA&#956;a> > 0. Após os cálculos explícitos, uma discussão sobre as conseqüências físicas de um parâmetro de Gribov não nulo é apresentada. Finalmente, apresentamos um estudo das ambiguidades de Gribov nos calibres lineares covariantes para o caso em que &#945;<<1, onde &#945; é o parâmetro de calibre. Após identificar uma região no espaço funcional das configurações na qual não existem cópias de Gribov próximas, efetuamos a respectiva restrição da integral de caminho. Como efeito no nível árvore, o propagador do glúon transverso se torna suprimido no limite infravermelho devido a presença do horizonte de Gribov. A componente longitudinal se mostra suprimida devido a geração dinâmica de massa, associada ao condensado <A&#956;aA&#956;a>. Ainda, diferentemente do calibre de Landau, o propagador dos campos fantasmas não apresenta conexão com forças de longo alcance. Em contrapartida, uma função de Green singular no infravermelho, relacionada ao horizonte, é identificada e pode ser associada a forças de longo alcance. Por fim, todos os resultados do calibre de Landau são recuperados no limite &#945;&#8594;0.. / Some nonperturbative aspects of Euclidean Yang-Mills theories in four dimensions,quantized in the Landau gauge, are analytically studied. In particular, we investigate the dynamical mass generation for the gluons due to the presence of dimension two condensates. This study is performed in the framework of the local composite operator technique in the case of the Yang-Mills action as well as in the case of the Gribov-Zwanziger action. Further, an investigation of the Gribov ambiguities in the linear covariant gauges is presented. In the case of the Yang-Mills action, we perform a detailed analysis of the local composite operator formalism when the operators AaAa and fabccbcc are simultaneously introduced. Using the algebraic renormalization theory, we prove the renormalizability of the model trough all orders in perturbation theory. With the help of the renormalization group equations, a quantum efective action for the condensates <AaAa> and <fabccbcc> is constructed. This construction is performed by means of the dimensional regularization in the MS renormalization scheme. We show that non vanishing condensates values are dynamically favored, independently of the chosen scale. Explicit one loop computations are then presented, providing estimates for the condensates as well as for the vacuum energy. With the help of suitable Ward identities, we are able to normally show that the presence of the condensate <fabccbcc> is responsible for the breaking of the transversality of the vacuum polarization. However, the gluon propagator remains transverse, trough all orders in perturbation theory. Finally, we end this analysis with the explicit computation of the one loop correction to the efective gluon mass. The result is that, due to the condensate <fabccbcc>, the Abelian and the non Abelian sectors acquire diferent masses. Since the non Abelian mass is larger than the Abelian one, this feature can be interpreted as an evidence for the Abelian dominance principle in the Landau gauge. With respect to the Gribov-Zwanziger action, we start our analysis without taking into account the condensate. We show that, at one loop order, the vacuum energy is always positive, independently of the renormalization scheme and scale. We also present attempts to solve the one and two loops horizon condition in the MS scheme, and also the respective obstacles of it. Later, using the algebraic renormalization theory, we show, to all orders in perturbation theory, the renormalizability of the Gribov-Zwanziger action when the composite operator AaAa is included in the framework of the local composite operator technique. Attempts to solve the one loop gap equations in the MS scheme are then presented. We show that there are no solutions for <AaAa> < 0 while for <AaAai> 0 there is only one possible solution for the horizon condition. However, in the MS scheme, we were not able to find explicitly that solution. As an improvement, an optimization of the renormalization scheme is performed in the sense of minimizing the renormalization scheme dependence. In that approach the MS limit solution was found as well as the solution with minimal dependence on the renormalization scheme. In both cases, the vacuum energy shows itself to be positive while the condensate <AaAa> > 0. A discussion of the consequences of a nonvanishing Gribov parameter is then provided. Finally, we present a study of the Gribov ambiguities in the linear covariant gauges for the case &#945;<<1, where &#945; is the gauge parameter. After the identification of a region in field space where there are no close Gribov copies, we perform the respective restriction in the path integral. As a tree level efect, the transverse gluon propagator turns out to be infrared suppressed, due to the presence of the Gribov horizon. The longitudinal component shows itself to be infrared suppressed due to the dynamical mass, associated with the condensate <AaAa>. Further, diferently of the Landau gauge, the ghost propagator is not related to the appearance of long range forces. Instead, an infrared singular Green function related to the Gribov horizon is identifed. This Green function can be associated with long range forces. At the end, all Landau gauge results can be recovered taking the limit &#945;&#8594;0.

Nós utilizamos as Regras de Soma da QCD para estudar a natureza dos mésons observados recentemente Y (4260), Y (4360) e Y (4660), e que são candidatos a estados exóticos de tetraquark (c¯cq¯q) ou (c¯cs¯s) com números quânticos JPC = 1. Nós trabalhamos com o termo dominante em s, com as contribuições dos condensados de dimensão mais alta e com termos lineares da massa do quark estranho ms. Nós obtivemos uma massa mY = (4.65 ± 0.11) GeV para o estado (c¯cs¯s) que é compatível com o valor experimental do Y (4660), enquanto que para o estado (c¯cq¯q) n´os obtivemos uma massa mY = (4.49 ± 0.11) GeV, que também é consistente com o valor experimental do Y (4360). Com a estrutura de tetraquark não foi possível explicar o Y (4260). Nós também consideramos os estados moleculares Ds0 ¯D s e D0 ¯D . Para a molécula Ds0 ¯D s nós obtivemos uma massa mDs0 ¯D s = (4.42 ±0.10) GeV que é consistente, considerando a incerteza, com a massa do méson Y (4360) e para a molécula D0 ¯D obtivemos mD0 ¯D = (4.27±0.10) GeV em excelente acordo com a massa do m´eson Y (4260). / We use QCD sum rules to test the nature of the recently observed mesons Y (4260), Y (4360) and Y (4660), assumed to be exotic four-quark (c¯cq¯q) or (c¯cs¯s) states with JPC = 1. We work at leading order in s, consider the contributions of higher dimension condensates and keep terms which are linear in the strange quark mass ms. We find for the (c¯cs¯s) state a mass mY = (4.65 ± 0.10) GeV which is compatible with the experimental candidate Y (4660), while for the (c¯cq¯q) state we find a mass mY = (4.49 ± 0.11) GeV, which is still consistent with the mass of the experimental candidate Y (4360). With the tetraquark structure we are working we can not explain the Y (4260) as a tetraquark state. We also consider molecular Ds0 ¯D s and D0 ¯D states. For the Ds0 ¯D s molecular state we get mDs0 ¯D s = (4.42 ± 0.10) GeV which is consistent, considering the errors, with the mass of the meson Y (4360) and for the D0 ¯D molecular state we get mD0 ¯D = (4.27±0.10) GeV in excelent agreement with the mass of the meson Y (4260).

Nesta dissertação nós revisamos aspectos gerais de teorias de gauge, os princípios da formulação de rede da cromodinâmica quântica (QCD) e algumas propriedades de quarkônios pesados, i.e. estados ligados de um quark pesado e seu antiquark. Como um exemplo de simulações de Monte Carlo de modelos de rede, apresentamos aplicações nos casos do oscilador harmônico e teorias de gauge SU(2). Nós estudamos o efeito de incorporar o propagador de gluon de simulações na rede em um modelo de potencial para a descrição do quarkônio, no caso do botômomio e do charmônio. Nós usamos em ambos os casos uma abordagem numérica para calcular as massas dos estados de quarkônio. O espectro resultante é comparado em ambos os casos com cálculos usando o potencial de Coulomb mais linear (ou potencial Cornell). / In this dissertation we review general aspects of gauge theories, the principles of the lattice formulation of quantum chromodynamics (QCD) and some properties of heavy quarkonia, i.e. bound states of a heavy quark and its antiquark. As an illustration of Monte Carlo simulations of lattice models, we present applications in the case of the harmonic oscillator and SU(2) gauge theory. We study the effect of incorporating the gluon propagator from lattice simulations into a potential model for the description of quarkonium, in the case of bottomonium and charmonium. We use a numerical approach to evaluate masses of quarkonium states. The resulting spectrum is compared in both cases to calculations using the Coulomb plus linear (or Cornell) potential.

L'avènement du LHC marque le début d'une ère de haute précision en physique des particules. Dans cette thèse de doctorat, nous abordons avec des outils innovants deux processus clés des collisionneurs de hadrons: la production inclusive de jets, et la production du boson de Higgs par fusion de bosons vecteurs (VBF). Dans la première partie de cette thèse, nous montrons comment resommer les premiers ordres logarithmiques de rayon de jet R, et appliquons ce formalisme à une étude approfondie du spectre inclusif des jets. Nous étudions les termes dépendant de R au troisième ordre non-nul (next-to-next-to-leading-order, NNLO), et les intégrons dans notre calcul. Nous examinons les éliminations dans la dépendance d'échelle, conduisant à une nouvelle prescription pour l'évaluation des incertitudes, et vérifions l'impact d'effets non-perturbatifs. Dans la deuxième partie de cette thèse, nous étudions les corrections de chromodynamique quantique dans la production de Higgs par VBF. En utilisant l'approche des fonctions de structure, nous calculons les corrections de quatrième ordre non-nul (NNNLO) à la section efficace inclusive. Nous calculons ensuite les corrections NNLO entièrement différentielles à la production de Higgs par VBF. Nous montrons que ces contributions sont significatives après coupures VBF, se trouvant en dehors des bandes d'incertitude d'échelle NLO. / With the advent of the LHC, particle physics has entered an era where high precision is required. In this thesis, we tackle two of the key processes at hadron colliders using innovative tools: inclusive jet production and Higgs production through vector-boson fusion (VBF). In the first part of this thesis, we show how to resum leading logarithmic terms of the jet radius R, and apply this formalism to a detailed study of the inclusive jet spectrum. We study subleading R-dependent terms at next-to-next-to-leading order (NNLO), and incorporate them into our calculation. We investigate cancellations in the scale dependence, leading to new prescriptions for evaluating uncertainties, and examine the impact of non-perturbative effects. In the second part of the thesis, we study QCD corrections in VBF-induced Higgs production. Using the structure function approach, we compute the next-to-next-to-next-to-leading order (NNNLO) corrections to the inclusive cross section. We then calculate the fully differential NNLO corrections to VBF Higgs production. We show that these contributions are substantial after VBF cuts, lying outside the NLO scale uncertainty bands.

Le but de cette thèse est l'étude des fonctions de corrélation des théries Yang-Mills dans le régime infrarouge. Il est connu que, à cause de l'invariance jauge, il est nécessaire de fixer la jauge pour calculer des valeurs moyennes analytiquement. La procedure de fixation gauge standard est la procedure de Faddeev-Popov (FP). Le Lagrangien de FP permet de faire des calculs perturbatifs pour la Chromodynamique Quantique dans le régime de hautes énergies dont les résultats sont comparés avec succès avec des expériences. Cependant, dans le régime de basses énergies, il se trouve que la constante de couplage, calculée avec la procedure antérieure, diverge. En conséquence, la théorie des perturbations standard n'est plus valide. D'autre part, les simulations du réseau trouvent que la constante de couplage est finie avec une valeur modérée même dans le régime infrarouge. Ceci suggère qu'il devrait exister une manière de faire des calculs perturbatifs également dans le régime infrarouge. Cette différence dans la constante de couplage peut être due au fait que la procedure de FP n'est pas bien justifiée dans ce régime. Nous proposons de modifier le Lagrangien de FP avec un terme massif pour les gluons. Cette modification est également justifiée par le fait que le réseau trouve un propagateur du gluon qui paraît massive aux basses énergies. Nous utilisons cette version massive pour calculer à une boucle les fonctions de corrélations à deux et trois points pour une configuration cinématique générale et en dimension quelconque dans la jauge de Landau. On trouve que les comparaisons de notre calcul à une boucle avec les résultat du réseau donnent, en géneral, un très bon accord. / The aim of this thesis is to investigate the infrared behaviour of Yang-Mills correlation functions. It is known that the gauge invariance of the theory brings as a consequence the necessity of a gauge fixing procedure in order to compute expectation values analytically. The standard procedure for fixing the gauge is the Faddeev-Popov (FP) procedure which allows one to do perturbation theory in the ultraviolet regime. Perturbative calculations using the FP gauge fixed action successfully reproduce Quantum Chromodynamics observables measured by experiments in the ultraviolet regime. In the infrared regime the coupling constant of the theory computed with the above procedure diverges, and standard perturbation theory does not seem to be valid. However, lattice simulations show that the coupling constant takes finite and not very large value. This suggests that some kind of perturbative calculations should be valid even in the infrared regime. The theoretical justification for the FP procedure depends on the absence of Gribov copies and hence is not valid in the infrared regime (where such copies exist). To correct this we propose to add a mass term for the gluons in the gauge-fixed Lagrangian. The gluon mass term is also motivated by lattice simulations which observe that the gluon propagator behaves as it was massive in the infrared regime. We use this massive extension of the FP gauge fixed action to compute the one loop correction of the two- and three-point correlation functions in the Landau gauge for arbitrary kinematics and dimension. Our one-loop calculations are enough, in general, to reproduce with good accuracy the lattice data available in the literature.

This PhD dissertation presents the measurement of the cross section of jet production in association with a Z boson in proton-proton collisions at the Large Hadron Collider in CERN, with a center-of-mass energy of 8 TeV in 2012 and of 13 TeV in 2015. The data used for this analysis were collected by the Compact Muon Solenoid (CMS) detector, with an integrated luminosity of 19.6 fb-1 in 2012 and of 2.25 fb-1 in 2015. The differential cross section is measured as a function of jet multiplicity, jet transverse momentum and rapidity, and the scalar sum of jet transverse momenta. The rapidity correlations between the Z boson and jets are also measured benefiting from the large statistics of data taken in 2012. All distributions of measured observables are obtained after correcting detector effects using unfolding approach, and the results of two leptonic decaying channels of Z boson are combined. Coming along with the systematic and statistical uncertainties, the measurement is compared to different theoretical predictions at different accuracy levels. The predictions are from MADGRAPH 5, SHERPA 2 (for 8 TeV analysis only), MADGRAPH_AMC@NLO, and fixed next-to-next-to-leading order (for 13 TeV analysis only). Thanks to the unprecedented high energy and the large statistics of data, precision measurement is accomplished in a physical phase space never reached before. This measurement provides precise systematics for different theoretical models. It also quantifies the improvement with higher order of perturbative quantum chromodynamics calculations on matrix elements relative to the leading order multi-leg approach. In particular to the rapidity correlation study, new matching schemes (FxFx and MEPS@NLO) for next-to-leading order matrix elements and parton shower show significant improvements with respect to the MLM matching scheme for leading order multi-leg matrix elements and parton shower. This measurement also gives precise background estimation for the measurements of many other processes in Standard Model like top quark production and gauge boson couplings, and for new physics searches such as Supersymmetry. In this thesis, the jet energy correction and calibration for the high level trigger system of CMS are also depicted. From 2012 to 2015, the Large Hadron Collider was upgraded, not only with the center-of-mass energy of the beams enlarged, but also with the instantaneous luminosity increased. The time distance between two particle bunches in a beam is reduced. As a result, the reconstructed momenta of the jets produced in each bunch crossing are significantly contaminated by multiple interactions. A dedicated technical approach has been developed for correcting the reconstructed jet momenta. The corrections have been calibrated and configured for the data taking in 2015 and 2016. / Cette thèse présente une mesure de la section efficace de production de jets associés à un boson Z dans les collisions proton-proton du Grand Collisionneur de Hadron (LHC) situé au CERN, avec des énergies dans le centre de masse de 8 TeV et 13 TeV, respectivement pour les années 2012 et 2015. Les données utilisées pour cette analyse ont été collectées par le détecteur Compact Muon Solenoid (CMS). Elles constituent des échantillons de luminosités intégrées de 19.6 fb⁻¹ et 2.25 fb⁻¹, respectivement pour 2012 et 2015. Nous mesurons la section efficace différentielle en fonction de la multiplicité de jets, de l’impulsion transverse et de la rapidité des jets, et en fonction de la somme scalaire des impulsions transverses des jets. La corrélation entre les rapidités du boson Z et des jets est aussi mesurée et bénéficie de la large statistique prise en 2012. Toutes les distributions d’observables mesurées sont obtenues après corrections pour les effets détecteurs et les résultats des canaux de désintégration muonique et électronique du boson Z sont combinés. Tenant compte des incertitudes statistiques et systématiques, les mesures sont comparées à différentes prédictions théoriques ayant différents niveaux de précision. Les prédictions sont obtenues de MADGRAPH 5, SHERPA 2 (pour l’analyse à 8 TeV uniquement), MADGRAPH_AMC@NLO, et un modèle fixé au NNLO (pour l’analyse à 13 TeV uniquement). Par ces mesures de précisions, et en particulier celle de la corrélation de rapidités, nous avons acquis une compréhension plus approfondie de la chromodynamique quantique dans son régime perturbatif. Grâce à la plus haute énergie jamais atteinte en laboratoire, et à la grande statistique disponible, nous avons sondé avec précision des endroits de l’espace des phases jusque là inaccessibles.Dans cette thèse, les corrections et la calibration de l’énergie des jets pour le haut niveau de sélection de CMS est également présentée. Durant la période de 2012 à 2015, le LHC a été amélioré, non seulement l’énergie dans le centre de masse a augmenté, mais la luminosité instantanée a aussi été amplifiée. L’écart temporelle entre deux paquets de particules dans les faisceaux du LHC a été réduite. L’une des conséquences est que l’impulsion reconstruite pour les jets produits lors d’un croisement de faisceau à une contribution significative venant des multiples interactions ayant lieux lors du croisement des paquets. Une approche technique dédiée a été développée pour corriger l'impulsion des jets. Les corrections obtenues ont été calibrées aux données prises en 2015 et 2016. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This thesis familiarizes the reader with the process behind the construction of ππ scattering amplitudes. Several representations and transformations nec- essary to pass from one to another are introduced. Then known solutions of Roy equations are employed to extract values of subthreshold parameters αππ and βππ from recent experimental data. As a second goal three-flavour chiral perturbation theory(χPT), which is a low energy effective field theory of quan- tum chromodynamics, is used to obtain theoretical predictions for αππ and βππ by applying a technique called resummed approach. A large statistical ensemble of predictions is numerically generated. Subsequently, Bayesian statistics is uti- lized to get more information about spontaneous symmetry breaking parameters X(3), Y (3), Z(3), which are related to the leading order low energy coupling constants of three-flavour χPT. These results are then compared to several other recent determinations. Significant shifts in probability distributions compared to Descotes-Genon et al. [2004] are observed. The new results are more consistent with theoretical expectations. 1 Bibliography S. Descotes-Genon, N. H. Fuchs, L. Girlanda, and J. Stern. Resumming qcd vac- uum fluctuations in three-flavor chiral perturbation theory. The European Phys- ical Journal C,...

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