To see the other types of publications on this topic, follow the link: Quantum chromodynamics QCD.
Dissertations / Theses on the topic 'Quantum chromodynamics QCD'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Quantum chromodynamics QCD.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Dowrick, Nigel. "Non-peturbative QCD." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236231.
Full text
2
Ashley, Jonathan D. "Investigations in non-perturbative QCD." Title page, abstract and table of contents only, 2004. http://hdl.handle.net/2440/37959.
Full textAbstract:
In this thesis we review two methods for studying the non-pertubative region of QCD: the effective field theory, chiral perturbation theory (χPT), and the cloudy bag model, a successful chiral quark model of hadron structure. We use information from both of these sources to construct a simple extrapolation formula in the pion mass, mπ, for the nucleon electromagnetic form factors, which combines the correct non-analytic chiral behaviour predicted by (χPT), with the correct large mπ behaviour. This formula is applied to recent quenched lattice QCD results to extrapolate to the physical regime. Given the simple nature of the extrapolation scheme, our results compare surprisingly well with experiment. We also employ a simple chiral quark model (the hedgehog) to examine the volume and pion mass dependence of the axial coupling constant, ga, along with the hedgehog baryon mass. Our results for ga reveal large volume dependence at low pion masses.Thesis (M.Sc.)--School of Chemistry and Physics, 2004.
3
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.
Full text
4
Gray, Norman. "Dimensionally regulated on-shell renormalisation in QCD and QED." Thesis, n.p, 1991. http://oro.open.ac.uk/19423/.
Full text
5
McCallum, Paul. "Upsilon spectroscopy using lattice QCD." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363170.
Full text
6
Portelli, Antonin. "Nonpertubative quantum chromodynamics and isospin symmetry breaking." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4110.
Full textAbstract:
Depuis les années 1930, on sait que le noyau des atomes est composé de deux types de particules: les protons et les neutrons. Ces deux particules sont très similaires: d'une part le neutron est subtilement plus lourd (un pour mille) que le proton et d'autre part le proton porte une charge électrique positive tandis que le neutron est neutre. La petite différence de masse entre le neutron et le proton fourni l'énergie suffisante pour autoriser désintégration où un neutron se désintègre en un proton en émettant un électron et un anti-neutrino électronique. Aussi, le fait que le proton ne se désintègre pas assure la stabilité de l'atome d'hydrogène. De plus, on sait empiriquement que les paramètres de la désintégration déterminent la composition des noyaux d'atomes stables plus lourds que l'hydrogène. Il est donc raisonnable de penser que si la différence de masse entre le neutron et le proton était de signe opposé ou seulement légèrement différente, l'Univers visible serait surement très différent de celui que l'on connait. Il est donc essentiel de comprendre l'origine de cette différence de masse à partir des principes premiers de la physique. C'est à ce problème, et à des problèmes liés à celui-ci, qu'essaye de répondre ce travail. Dans la compréhension actuelle de la physique, les neutrons et les protons sont des particules composées de particules élémentaires appelées quark up (symbole u) et quark down (symbole d). Le proton est un état lié uud et le neutron est un état lié udd. Les quarks up et down sont deux particules similaires: elles sont toutes deux légères (de l'ordre de quelques MeV) et leurs charges électriques sont différentes
7
Campbell, N. A. "Static potentials in lattice QCD." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377123.
Full text
8
Sharan, Ujjawal. "Topology and chiral symmetry breaking in QCD." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302137.
Full text
9
Hill, Victor John. "Heavy flavour physics from lattice QCD." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252696.
Full text
10
Heatlie, Grant James. "Aspects of phenomenology from lattice QCD." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303058.
Full text
11
Turner, Miriam Frances. "Tests of QCD at the Z'0 resonance." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239763.
Full text
12
Bawa, Ahmed Cassim. "Phenomenology of QCD and electroweak processes." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/10487/.
Full textAbstract:
A phenomenological study is made of several aspects of the standard model (and beyond) in the context of collider physics. These calculations are performed in the framework of Quantum Chromodynamics (QCD) and the standard Elec-troweak theory in an attempt to understand the underlying gauge theory more fully. In chapter 2, a precision QCD and electroweak calculation is performed to predict the high transverse-momentum distribution of the intermediate vector bosons produced in pṕ collisions. Calculated cross-sections are compared with data from the CERN collider and predictions are made for the Tevatron, LHC and SSC. Theoretical uncertainties, due to scale and structure function ambiguities, are estimated. In chapter 3, the equivalent photon approximation (or EPA) is studied at high energies to determine the accuracy of the approximation. An exact calculation of the process e + q → e + q + γ is performed and compared with an approximate calculation of the process γ+q → γ+q , where the initial-state photon is produced (using the EPA) from an initial-state electron. The test is carried out for the cases where the final-state electron are tagged and untagged. At high energies, the approximation is accurate to within 10%. In chapter 4, deep inelastic Compton scattering is investigated at energies of the HERA ep collider. A study of the production rate is made to determine the feasibility of measurement at HERA and it is clear that for pT < 50 GeV/c the cross-section will be measurable. In addition, studies are made to determine the efficiency of this process as a probe of the proton structure functions. The cross-section is only weakly dependent on the structure functions. In chapter 5, the production of charged Higgs scalars is considered at hadron colliders. The fully inclusive cross-section for charged Higgs scalars is calculated and compared with the associated W boson cross-section. The generic process g+b →b+t + t, which may proceed through an intermediate charged Higgs (or W) or through QCD processes, is studied and the Higgs cross-sections are compared with the W and QCD cross-sections.
13
Chamoun, Nidal. "QCD sum rules and their applications to deep inelastic scattering." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320232.
Full text
14
Gray, Alan. "Upsilon spectroscopy and leptonic decays using fully unquenched lattice QCD." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274769.
Full text
15
Ford, I. J. "Aspects of pure quantum chromodynamics on large lattices." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382631.
Full text
16
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.
Full text
17
Sanielevici, S. (Sergiu). "Phenomenological implications of calculations in nonperturbative QCD." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74001.
Full text
18
Page, Philip R. "The ratio gA/gV in cavity QCD." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/17390.
Full textAbstract:
Bibliography: pages 96-98.BRS invariant quantum chromodynamics in a spherical cavity is developed using canonical quantization. The weak vector and axial form factors are defined, employing a classical external W- field. The Gell-Mann and Low theorem is extended to include non-diagonal matrix elements and degenerate perturbation theory. The Sucher form of the Gell-Mann and Low theorem is employed to calculate corrections of order GFg² in the weak and strong coupling constants to gA and gv for neutron beta decay. Up and down quarks are assumed massless. The gauge-independent divergences from the loop diagrams cancel each other and can be regularized dimensionally, making renormalization unnecessary. We find that the weak vector and axial current coupling constants are respectively: 9v = 1.0000 gA = 1.0883 + 0.2425 αs', where the preferred value of αs = 2.2 in the M.I.T. bag model gives gA = 1.62.
19
Tsang, Wai Yeung. "Hadronic jet production at the CERN UA2 detector : an experimental test of QCD." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254216.
Full text
20
Nail, Graeme. "Quantum chromodynamics : simulation in Monte Carlo event generators." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/quantum-chromodynamics-simulation-in-monte-carlo-event-generators(46dc6f2e-1552-4dfa-b435-9608932a3261).html.
Full textAbstract:
This thesis contains the work of two recent developments in the Herwig general purpose event genrator. Firstly, the results from an new implementation of the KrkNLO method in the Herwig event generator are presented. This method allows enables the generation of matched next-to-leading order plus parton shower events through the application of simple positive weights to showered leading order events. This simplicity is achieved by the construction Monte Carlo scheme parton distribution functions. This implementation contains the necessary components to simulation Drell-Yan production as well as Higgs production via gluon fusion. This is used to generate the first differential Higgs results using this method. The results from this implementation are shown to be comparable with predictions from the well established approaches of POWHEG and MC@NLO. The predictions from KrkNLO are found to closely resemble the original configuration for POWHEG. Secondly, a benchmark study focussing on the source of perturbative uncertainties in parton showers is presented. The study employs leading order plus parton shower simulations as a starting point in order to establish a baseline set of controllable uncertainties. The aim of which is to build an understanding of the uncertainties associated with a full simulation which includes higher-order corrections and interplay with non- perturbative models. The uncertainty estimates for a number of benchmark processes are presented. The requirement that these estimates be consistent across the two distinct parton show implementations in Herwig provided an important measure to assess the quality of these uncertainty estimates. The profile scale choice is seen to be an important consideration with the power and hfact displaying inconsistencies between the showers. The resummation profile scale is shown to deliver consistent predictions for the central value and uncertainty bands.
21
Bilson-Thompson, Sundance Osland. "Investigation of topology, instantons, and the Nahm transform in lattice QCD using highly improved operators." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phb5996.pdf.
Full text
22
Morales, P. S. (Patrícia Soares). "Limite de acoplamento forte da QCD e a interação méson-méson /." São Paulo, 2002. http://hdl.handle.net/11449/91868.
Full textAbstract:
Orientador: Gastão Inácio KreinBanca: Tobias Frederico
Banca: Sadhan Kumar Adhikari
Resumo: O mecanismo de rearranjo de tubos de fluxo predito no limite de acoplamento forte da formulação Hamiltoniana da QCD na rede foi implementado num modelo de quarks constituintes e suas consequências investigadas para o espalhamento méson-méson. O rearranjo de tubos de fluxo leva a efeitos similares aos tradicionais efeitos de troca de quarks com troca de um glúon em interações hádron-hádron. Contudo, enquanto o primeiro está relacionado ao regime de confinamento da QCD, o último está relacionado ao regime de liberdade assintótica desta teoria. Mostra-se aqui que ambos mecanismos levam a resultados qualitativamente similares quando o potencial de rearranjo pode ser escrito como a soma de interações locais quark-quark, antiquark-antiquark e quark-antiquark. Para interações gerais, não locais e de longo alcance, o rearranjo de tubos de fluxo leva a resultados qualitativa e quantitativamente diferentes dos resultados de troca de quarks com troca de um glúon. As consequências disso para a fenomenologia das interações hádron-hádron são discutidas.
Abstract: The mechanism of link rearrangement predicted in the strong coupling limit of Hamiltonian lattice QCD is implemented in a constituent quark model and its consequences for meson-meson scattering are investigated. Link rearrangement leads to effects similar to the traditional quark exchange with one gluon exchange in hadron-hadron interactions. However while the first is related to the confinement regime of QCD, the latter is related to the asymptotic freedom regime of this theory. It is shown here that both mechanisms lead to identical qualitative results when the rearrangement potential can be written as a sum of local quark-quark, antiqurk-antiquark e quark-antiquark. For general, long-range nonlocal interactions, link rearrangement leads to results qualitative and quantitatively different from those of quark exchange with one gluon exchange. The consequences of this for the phenomenology of hadron-hadron interactions are discussed.
Mestre
23
Harrison, Judd Gavin Ivo Henry. "Lattice QCD determination of weak decays of B mesons." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/286066.
Full textAbstract:
This thesis uses a variety of numerical and statistical techniques to perform high precision calculations in high energy physics using quantum field theory. It introduces the experimental motivation for the calculation of B meson form factors and includes a discussion of previous work. It then describes the modern theoretical framework describing these phenomena, outlining quantum chromodynamics and electroweak theory, and then illustrating the procedure of gauge fixing, the quantum effective action and background field gauge which is required for subsequent perturbative work. Details of the basic methodology of lattice quantum field theory are given as well as the specific formulation of the relativistic theory and nonrelativistic approximations used in this work to describe quantum chromodynamics. A comprehensive calculation of the zero recoil B to D* form factor is then presented, using state of the art lattice techniques with relativistic charm sea quarks and light sea quarks with correct physical masses, leading to a discussion of the dominant sources of uncertainty and possible resolutions of experimental tensions. Also included is preliminary work towards the full calculation of nonzero recoil matrix elements, with the aim of outlining possible future work. Finally, this thesis presents the computation of parameters correcting for radiative one loop phenomena and corrections to the kinetic coupling parameters in nonrelativistic quantum chromodynamics in order to achieve a desirable level of precision in future calculations. This is done using Monte-Carlo integration to evaluate integrals from diagrams generated using automated lattice perturbation theory in background field gauge in order to match the coefficients of the effective action between the lattice and the continuum.
24
Luffman, Pateick Edward. "Performance of track reconstruction in ZEUS central tracking & studies of QCD in electron-proton collisions at HERA." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358583.
Full text
25
Peláez, Arzúa Monica Marcela. "Infrared correlation functions in Quantum Chromodynamics." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066491/document.
Full textAbstract:
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 accordThe 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
26
Van, de Water Ruth S. "Applications of chiral perturbation theory to lattice QCD /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9730.
Full text
27
Lim, Matthew Alexander. "Quantum chromodynamics and the precision phenomenology of heavy quarks." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/285109.
Full textAbstract:
In this thesis we consider the phenomenology of the theory of strong interactions, Quantum Chromodynamics (QCD), with particular reference to the ongoing experimental program at the Large Hadron Collider in CERN. The current progress in precision measurement of Standard Model processes at the LHC experiments must be matched with corresponding precision in theoretical predictions, and to this end we present calculations at next-to-next-to-leading order in perturbation theory of observable quantities involving quarks and gluons, the strongly interacting particles of the SM. Such calculations form the most important class of corrections to observables and are vital if we are to untangle signals of New Physics from LHC data. We consider in particular the amplitudes for five parton interactions at 1- and 2-loop order and present full (in the 1-loop case) and partial (in the 2-loop case) analytic results in terms of rational functions of kinematic invariants multiplying a basis of master integrals. We address the problem of the solution of a system of integration-by-parts identities for Feynman integrals and demonstrate how some current difficulties may be overcome. We consider also the properties of the top quark, and present the NNLO, real-virtual contributions to the calculation of its decay rate. The results are presented as helicity amplitudes so that the full behaviour of the top spin is retained. These amplitudes constitute a necessary ingredient in the complete calculation of top quark pair production and decay at NNLO which will be an important theoretical input to many experimental analyses. Turning to a more phenomenological study, we consider the extraction of two important SM parameters, the top mass and the strong coupling constant, from measurements of top pair production at the ATLAS and CMS experiments. We compare with NNLO theory predictions and use a least-squares method to extract the values of the parameters simultaneously. We find best fit values of the parameters which are compatible with previous extractions performed using top data with the current world averages published by the Particle Data Group. We consider the issue of PDF choice and the circumstances in which a heavy quark can be considered a constituent of the proton. In particular, we look at the production of a Higgs boson in association with bottom quarks in four and five flavour schemes, in which the b may or may not be included in the initial state. We show that theoretical predictions in both schemes are well-motivated and appropriate in different scenarios, and moreover that results in the schemes are consistent provided a judicious choice of the renormalisation and factorisation scales is made. We suggest a typical scale choice motivated by considerations of consistency and find it to be somewhat lower than the typical hard scale of the process.
28
Oliveira, Fabiane Avena de. "Consequências macroscopicas de algumas propriedades da QCD." Universidade de São Paulo, 1995. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-28022014-111310/.
Full textAbstract:
No presente trabalho, investigamos algumas propriedades da qcd quando incorporadas aos modelos efetivos. Mostramos que muitas propriedades da materia densa quente ou fria podem ser melhor descritas a partir do modelo quiral SIGMA-OMEGA. Mostramos que, em contraste com o modelo renormalizado de walecka, as correcoes de vacuo sao cruciais para uma adequada descricao da materia nuclear densa. Estes resultados tambem sao confirmados a partir das previsoes feitas para estrelas de neutrons. Um possivel sinal da transicao de fase em colisoes de ions pesados relativisticos e tambem calculado pela observacao das taxas de decaimento do pion nos canais PI POT.-SETAMU POT. -+NU IND.MU e PI POT.-SETAVARRHO POT.-+SETAVARRHO POT.-+NU IND.VARRHO. Mostramos que as propriedades de confinamento e liberdade assintotica, incorporadas pelo modelo de sacola do mit, dao suporte para a especulacao da possivel existencia de estrelas hibridasIn this work we investigate some properties of QCD as incorporated in effective models. We show that several properties of cold or hot and dense nuclear matter can be well described in the context of the chiral - model. We show that, in contrast to the nom chiral Walecka model vacuum renormalization corrections are crucial to provide for an adequate description. This result is also confirmed in the description of neutron stars. A possible signature of chiral phase transition in RHI collisions is also pointed out in the observation of the ratio of pion decay in the two channels POT. POT. + IND. and POT. e POT. + IND. e. We also show that the properties of confinement and asymptotic freedom as incorpored by the Bag model give support to the speculation on the existence of hybrid stars.
29
Karlberg, Alexander. "At the frontier of precision QCD in the LHC era." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:73cc8cf7-da8b-4845-b015-be0313ae0493.
Full textAbstract:
This thesis discusses recent advances in precision calculations of quantum chromodynamics and their application to the Large Hadron Collider (LHC) physics program and beyond. The first half of the thesis is dedicated to the study of vector boson fusion Higgs (VBF) production; fully differential at the next-to-next-to-leading order level (NNLO), and inclusively at next-to-next-to-next-to-leading order (N3LO). Both calculations are performed in the structure function approximation, where the VBF process is treated as a double deep inelastic scattering. For the differential calculation a new subtraction method, "projection-to-Born", is introduced and applied. We study VBF production in a number of scenarios relevant for the LHC and for Future Circular Colliders (FCC). We find NNLO corrections after typical cuts of 5-6% while differential distributions show corrections of up to 10-12% for some standard observables. For the inclusive calculation we find N3LO corrections at the order of 1-2‰. The second half of the thesis presents recent results on the matching of fixed order calculations with parton showers. We first present the POsitive Weight Hardest Emission Generator (POWHEG) method for matching next-to-leading order (NLO) calculations with parton showers. We then proceed to apply it to the case of vector boson fusion ZZjj production and discuss the results for scenarios relevant for the LHC and a possible FCC. In order to present the matching of a NNLO calculation with a parton shower, we next discuss the Multi-Scale Improved NLO (MiNLO) procedure. By applying a reweighting procedure to MiNLO improved Drell-Yan production, we obtain a generator which is NNLO accurate when integrated over all radiation while providing a fully exclusive description of the final state phase space. We compare the calculation to dedicated next-to-next-to-leading logarithm resummations and find very good agreement. The generator is also found to be in good agreement with 7 and 8 TeV LHC data.
30
Shcheredin, Stanislav. "Simulations of lattice fermions with chiral symmetry in quantum chromodynamics." Doctoral thesis, [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97410907X.
Full text
31
Lesk, Victor Isaac. "Heavy-light hadron matrix elements from lattice QCD." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323943.
Full text
32
Chan, Chuan-Tsung. "Neutron electric dipole moment from QCD sum rules /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9708.
Full text
33
Alves, Ricardo Joao Gaio. "A convergent reformulation of perturbative QCD." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4259/.
Full textAbstract:
We present and explore a new formulation of perturbative QCD based not on the renormalised coupling but on the dimensional transmutation parameter of the theory and the property of asymptotic scaling. The approach yields a continued function, the iterated function being that involved in the solution of the two-loop β-function equation. In the so-called large-b limit the continued function reduces to a continued fraction and the successive approximants are diagonal Padé approximants. We investigate numerically the convergence of successive approximants using the leading-b approximation, motivated by renormalons, to model the all-orders result. We consider the Adler D-function of vacuum polarisation, the Polarised Bjorken and Gross-Llewellyn Smith sum rules, the (unpolarised) Bjorken sum rule, and the Minkowskian quantities R(_r) and the R-ratio of e(^+)e(^-) annihilation. In contrast to diagonal Fade approximants the truncated continued function method gives remarkably stable large-order approximants in cases where infra-red renormalon effects are important. We also use the new approach to determine the QCD fundamental parameters from the R(_r) and the R-ratio measurements, where we find Ā(^(3))(_MS)=516±48 MeV (which yields a(_s)(µ=m(_r))=0.360(^+0.021)(_=0.020)), and Ā(^(5))(_MS)=299(^+6)(_-7) MeV (which yields a(_s)(µ=m(_zo)=0.1218±0.0004), respectively. The evolution of the former value to the m(_zo) energy results in a(_s)(µ= m(_zo)) = 0.123 ± 0.002. These values are in line with other determinations available in the literature. We implement the Complete Renormalisation Group Improvement (CORGI) scheme throughout all the calculations. We report on how the mathematical concept of Stieltjes series can be used to assess the convergence of Padé approximants of perturbative series. We find that the combinations of UV renormalons which occur in perturbative QCD may or may not be Stieltjes series depending on the renormalisation scheme used.
34
Bennett, Edward. "Physical and computational applications of strongly-interacting dynamics beyond QCD." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa38186.
Full textAbstract:
In this thesis we investigate numerically SU(2) theories with Dirac—or Majorana—fermions in the adjoint representation. Majorana fermions have historically proven difficult to treat numerically; here, a change of basis is introduced that allows two Majorana fermions to be expressed in terms of one Dirac fermion. This also provides greater insight into the analysis of the properties of theories with Dirac fermions. Attention is focused on the SU(2) theory with a single Dirac flavour (or equivalently two Majorana flavours). Its lattice phase diagram, spectrum, and the anomalous dimension of the chiral condensate are investigated. We observe a long region of constant mass ratios and an anomalous dimension 0.9 ≲ γ∗ ≲ 0.95. The behaviour of the pion mass and the presence of a light scalar in particular point to behaviour that is not traditionally confining; instead the theory appears to lie in or near the conformal window. The topological susceptibility and instanton size distribution are also investigated, for the one-Dirac-flavour theory and additionally the pure-gauge and two-Dirac-flavour (Minimal Walking Technicolor) theories. The properties are found to not depend on number of flavours, indicating a quenching of the fermions in the topology, also consistent with (near-)conformal behaviour (as has previously been reported in studies of other observables for Minimal Walking Technicolor). The code used is described, and a high-performance computing benchmark developed from it is detailed. While the benchmark was originally developed to investigate the performance of different supercomputer architectures for the class of problems we are interested in. Due to the nature of the code on which it is based, it has an unusual flexibility in the demands it may place on machine’s performance characteristics, which may allow it to be applicable to problems outside of lattice physics. The benchmark is used to characterise a number of machines’ relative performance.
35
Anastasiou, Charalampos. "Two loop integrals and QCD scattering." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4385/.
Full textAbstract:
We present the techniques for the calculation of one- and two-loop integrals contributing to the virtual corrections to 2→2 scattering of massless particles. First, tensor integrals are related to scalar integrals with extra powers of propagators and higher dimension using the Schwinger representation. Integration By Parts and Lorentz Invariance recurrence relations reduce the number of independent scalar integrals to a set of master integrals for which their expansion in є = 2 — D/2 is calculated using a combination of Feynman parameters, the Negative Dimension Integration Method, the Differential Equations Method, and Mellin-Barnes integral representations. The two-loop matrix-elements for light-quark scattering are calculated in Conventional Dimensional Regularisation by direct evaluation of the Feynman diagrams. The ultraviolet divergences are removed by renormalising with the MS scheme. Finally, the infrared singular behavior is shown to be in agreement with the one anticipated by the application of Catani's formalism for the infrared divergences of generic QCD two-loop amplitudes.
36
Holanda, L. B. (Leandro Batista). "Um estudo sobre o fator de forma 'gkk*'pi'(q POT. 2)' usando regras de soma da QCD /." São Paulo, 2002. http://hdl.handle.net/11449/91857.
Full textAbstract:
Resumo: As Regras de Soma da QCD foram usadas para a obtenção do fator de forma no vértice 'capa'capa"AST"'pi' e das constantes de decaimento, 'F IND.'capa' e 'F IND.'capa"AST"'. O método das Regras de Soma da QCD se baseia no princípio da dualidade no qual assume-se que é possível descrever simultâneamente um hadron em dois níveis: em termos dos graus de liberdade de quarks e gluons (chamado de lado da QCD) e em termos de graus de liberdade hadronicos (chamado de lado fenomenológico). As constantes de decaimento ficaram de acordo com os resultados experimentais. Entretanto, nosso trabalho mostrou que a corrente axial, usada para descrever o kaon, não é apropriada para descrever o fator de forma.Abstract: The QCD Sum Rules had been used to evaluate the form factor in the vertex 'capa'capa"AST"'pi' and the decay constants, 'F IND.'capa' e 'F IND.'capa"AST"'. The method of QCD Sum Rules is based on the duality principle in which it is assumed that the hadrons can simultaneously be described in two levels: quarks and haadrons. The decay constants obtained are in good agreement with the experimental results. However, this work showed that the axial current, used to describe the meson k is not appropriate to study the form factor.
Orientador: Gastão Inácio Krein
Coorientador: Marina Nielsen
Banca: Miriam Enriquetta Bracco
Banca: Bruto Max Pimentel Escobar
Mestre
37
Wu, Jackson M. S. "Improvement of Wilson fermions and twisted mass lattice QCD /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9706.
Full text
38
Mason, David Alexander. "Measurement of the strange-antistrange asymmetry at NLO in QCD from NuTeV dimuon data /." view abstract or download file of text, 2006. http://wwwlib.umi.com/cr/uoregon/fullcit?p3211223.
Full textAbstract:
Thesis (Ph.D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 415-429). Also available for download via the World Wide Web; free to University of Oregon users.
39
Yedelkina, Yelyzaveta. "Vector-quarkonium production in photon-photon and photon-proton collisions up to one loop in quantum chromodynamics." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP077.
Full textAbstract:
Cette thèse se concentre sur l'une des particules les plus étudiées dans les collisionneurs à haute énergie, le quarkonium, qui est un état lié d'une paire de quarks et d'antiquarks lourds.Le partie I commence par une revue des principales caractéristiques de la théorie de l'interaction forte, appelée QCD, et discute le cadre de travail de la QCD Non-Relativiste (NRQCD) pour le calcul des sections efficaces de production et de désintégration du quarkonium, en se restreignant à l'état de Fock principal de la paire quark-antiquark, comme dans le Modèle Couleur-Singlet (CSM). Nous présentons ensuite notre méthodologie pour le calcul des corrections d'ordre sous-dominant (NLO) dans le couplage fort de la production de quarkonium vectoriel. En particulier, nous décrivons les principales étapes pour le calcul des corrections virtuelles et réelles. Pour effectuer ces calculs, nous avons développé un algorithme basé sur la soustraction en terme de dipole dits de Catani-Seymour et une implémentation numériquement efficace de la section efficace NLO avec le formalisme de la fonction d'échelle.Le partie II présente une sélection de nos résultats concernant la production de quarkonium dans diverses installations expérimentales telles que le LHC, l'HERA, le CEPC, le FCC, l'EIC et le CLIC. Nous avons étudié la production des états vectoriels du quarkonium J/psi et Upsilon dans la limite de la photoproduction des collisions lepton-hadron, où un photon quasi réel brise un proton pour produire le quarkonium avec au moins un parton dur en recul. En particulier, nous montrons que le CSM peut décrire les données H1 de HERA2. Pour cette étude, nous avons inclus une contribution induite par la QED via un photon virtuel. Celle-ci était considérée comme négligeable dans la littérature, mais devient la principale contribution pour les valeurs de l'impulsion transverse les plus grandes atteignables à l'EIC. Une autre contribution nouvelle que nous avons considérée est une production associée de J/psi et d'un autre quark charmé avec le schéma du nombre de saveurs variable. Ce processus peut être observé au futur EIC et peut être utilisé pour sonder le contenu non perturbatif du charme du proton à grande fraction d'impulsion. En outre, pour les processus de photoproduction dans les collisions lepton-hadron, nous avons étudié l'origine d'un comportement non physique des sections efficaces, qui s'est avéré être lié à une sur-soustraction des divergences colinéaires dans les fonctions de distribution des partons (PDF). La méthode de fixation d'échelle que nous avons utilisée résout ce problème au NLO dans le couplage fort, de sorte que nous avons pu fournir une analyse qualitative de la possibilité de contraindre les PDF en utilisant les futures données de photoproduction de J/psi et d'Upsilon (1S). Les sections efficaces présentées devraient être mesurables à des énergies élevées avec une très bonne précision au futur EIC et dans d'autres installations futures telles que le LHeC ou le FCC-eh. Les mesures à plus basse énergie effectuées à AMBER-COMPASS++ et à l'EICC peuvent être utiles pour sonder la région de valence.Le partie II comprend également une revue de notre étude, qui revisite le calcul NLO pour la production inclusive de J/psi via deux photons directs et un photon direct et un photon dit résolu dans la fusion de photons dans des collisions d'électron-positon. Elle inclut toutes les contributions significatives via des photons directs : la production via des photons directs d'un J/psi et d'un photon, la production associée de J/psi et d'une paire quark-antiquark charmées, et la production de J/psi et de trois gluons. Nous avons également pris en compte les contributions d'un photon direct et d'un photon dit résolu jusqu'au NLO en la constante de couplage. Nous avons fourni des prédictions phénoménologiques pour la cinématique des expériences DELPHI, CEPC, FCC-ee et CLIC, où toutes ces contributions CS ont été rassemblées pour la première foisThe thesis focuses on one of the most studied particles at high-energy colliders, the quarkonium, which is a bound state of a heavy quark-antiquark pair. Part I starts with a review of the main features of QCD, the theory of the strong interaction and discusses the Non-Relativistic QCD (NRQCD) framework for the calculation of the quarkonium-production cross sections and decay widths, restricted to the leading Fock state of the quark-antiquark pair, as in the Colour-Singlet Model (CSM). We then present our methodology for the computation of the next-to-leading order (NLO) corrections in the strong coupling to vector quarkonium production. In particular, the main steps of the calculation methodology of virtual and real corrections are described. To perform such calculations, we have developed an algorithm based on the Catani-Seymour dipole subtraction and a numerically efficient implementation of the NLO cross section with the scaling-function formalism. Part II presents a selection of our results for quarkonium production at various experimental facilities such as the LHC, HERA, the CEPC, the FCC, the EIC and the CLIC. We have studied the production of the vector quarkonium states J/psi and Upsilon in the photoproduction limit of lepton-hadron collisions, where a quasi on-shell photon breaks a proton to produce the quarkonium with at least one recoiling hard parton. In particular, we show that the CSM can describe the HERA2 H1 data. For this study we have included a QED-induced contribution via an off-shell photon which was thought to be negligible but which becomes the leading contribution at the largest transverse momenta accessible with the EIC. Another novel contribution we have considered is a J/psi and another charm quark associated production with the variable-flavour-number scheme. This process can be observed at the future EIC and can be used to probe the non-perturbative charm content of the proton at high momentum fractions. Furthermore, we have studied the origin of an unphysical behaviour of the photoproduction cross sections, which has been found to be related to an over-subtraction of collinear divergences in the parton distribution functions (PDFs). The scale-fixing method we have used solves this problem at NLO in the strong coupling, so we could provide a qualitative analysis of the possibility of constraining the PDFs using future J/psi and Upsilon (1S) photoproduction data. The cross sections we obtained show that the corresponding yields are expected to be measured at high energies with very good accuracy at the future EIC and other future facilities such as the LHeC or the FCC-eh. In addition, we have shown that the lower energy measurements at AMBER-COMPASS++ and the EicC can be useful to probe the valence region. The second part also includes a review of our study which revisits the inclusive NLO calculation for the J/psi production via direct photon and single-resolved photon in photon fusion in electron-positron collisions. Our study includes all significant direct-photon contributions: the direct-photon production of J/psi and a photon, the associated production of J/psi and a charm quark-antiquark pair, and the production of J/psi along with three gluons. We have also considered the single-resolved-photon contributions up to NLO in the coupling constant. We have provided phenomenological predictions for the kinematics of the DELPHI, the future CEPC, the FCC-ee and the CLIC experiments, where all these CS contributions have been brought together for the first time
40
Alvites, José Carlos Valencia. "Rigorous results for the particle spectrum of lattice quantum chromodynamics moldels in the strong coupling regime." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/55/55135/tde-09092016-144325/.
Full textAbstract:
In this thesis, using rigorous methods, we determine the low-lying energy-momentum spectrum of a lattice Quantum Chromodynamics model (QCD) in dimension 3 + 1, imaginary time and in the strong coupling regime. We consider a QCD model with the Wilson action, three quark avors and 4 X 4 Dirac spin matrices. Under these conditions, we reanalyze que question about the existence of baryon particles in the context of the Gell-Mann and Ne´eman Eightfold Way. Completing previous works, where the octet baryons where shown to exist, here we prove the existence of the decuplet baryons detected by showing the existence of isolated dispersion curves in the energy-momentum espectrum restricted to the subspace of the physical quantum-mechanical Hilbert H of the model, associated with states with an odd number of fermions. Besides, we obtain some smoothness properties veried by these curves, as well as analytical properties of the spectral measure for the two-baryon correlations. Also, the octet and the decuplet baryons are shown to be the only states in the odd subspace up to near the energy threshold of the meson-baryon bound state. Using the results obtained here, we can go up in the spectrum and validate some previously obtained results on the two-baryon bound state spectrum beyond the so called ladder approximation, for the complete model.Nessa tese, usando métodos rigorosos, determinamos a parte inicial do espectro de energia-momento para o modelo de Cromodinâmica Quântica (QCD) na rede, em dimensão 3 + 1, com tempo imaginário e no regime de acoplamento forte. Consideramos o modelo de QCD com a ação de Wilson, três sabores de quarks e matrizes de spin de Dirac 4 X 4. Sob estas condições, reconsideramos a questão da demonstração da existência de bárions, no contexto do Eightfold Way de Gell-Mann e Ne ´eman. Complementando trabalhos anteriores onde a existência dos octetos de bárions foi demonstrada, aqui demonstramos a existência dos decupletos de bárions. Estas partículas são detectadas através de curvas de dispersão isoladas no espectro de energia-momento do modelo, considerando-se o subespaço H0, do espaço de Hilbert (quântico) físico H, com vetores com um número ímpar de férmions. Além disso, obtemos propriedades de suavidade destas curvas, assim como propriedade analíticas da medida espectral da correlação de dois bárions. Estes bárions são demonstrados ser os únicos estados espectrais no modelo, no subespaço ímpar, até o limiar de energia próximo do estado méson-bárion. Com os resultados obtidos nesta tese, podemos subir no espectro e validar, para o modelo completo, resultados espectrais envolvendo estados ligados de dois-bárion obtidos anteriormente na chamada aproximação escada (dominante).
41
Mirjalili, Abolfazl. "Scale dependence and renormalon-inspired resummations for some QCD observables." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3825/.
Full textAbstract:
Since the advent of Quantum Field Theory (QFT) in the late 1940's, perturbation theory has become one of the most successful means of extracting phenomenologically useful information from QFT. In the ever-increasing enthusiasm for new phenomenological predictions, the mechanics of perturbation theory itself have taken a back seat. It is in this light that this thesis aims to investigate some of the more fundamental properties of perturbation theory. In the first part of this thesis, we develop the idea, suggested by C.J.Maxwell, that at any given order of Feynman diagram calculation for a QCD observable all renormalization group (RG)-predictable terms should be resummed to all-orders. This "complete" RG-improvement (CORGI) serves to separate the perturbation series into infinite subsets of terms which when summed are renormalization scheme (RS)-invariant. Crucially all ultraviolet logarithms involving the dimensionful parameter, Q, on which the observable depends are resummed, thereby building the correct Q-dependence. We extend this idea, and show for moments of leptoproduction structure functions that all dependence on the renormahzation and factorization scales disappears provided that all the ultraviolet logarithms involving the physical energy scale Q are completely resummed. The approach is closely related to Grunberg's method of Effective Charges. In the second part, we perform an all-orders resummation of the QCD Adler D-function for the vector correlator, in which the portion of perturbative coefficients containing the leading power of b, the first beta-function coefficient, is resummed to all-orders. To avoid a renormalization scale dependence when we match the resummation to the exactly known next-to-leading order (NLO), and next-NLO (NNLO) results, we employ the Complete Renormalization Group Improvement (CORGI) approach , removing all dependence on the renormalization scale. We can also obtain fixed-order CORGI results. Including suitable weight-functions we can numerically integrate these results for the D-function in the complex energy plane to obtain so-called "contour-improved" results for the ratio R and its tau decay analogue Rr. We use the difference between the all-orders and fixed-order (NNLO) results to estimate the uncertainty in αs(M2/z) extracted from Rr measurements, and find αs(M2/z) = 0.120±0.002. We also estimate the corresponding uncertainty in a{Ml) arising from hadronic corrections by considering the uncertainty in R(s), in the low-energy region, and compare with other estimates. Analogous resummations are also given for the scalar correlator. As an adjunct to these studies we show how fixed-order contour-improved results can be obtained analytically in closed form at the two-loop level in terms of the Lambert W-function and hypergeometric functions.
42
Cossu, Guido. "Deconfinement transition in QCD at finite temperature." Doctoral thesis, Scuola Normale Superiore, 2009. http://hdl.handle.net/11384/85831.
Full textAbstract:
The main subject of this thesis is the problem of confinement in QCD. Since the discovery
of quarks in high energy experiments, their absence as free particles in nature
became one of the hot topics in modern physics.
The non abelian gauge field theories developed in the 50s by Yang and Mills and
successively generalized in the Standard Model have proved successful in describing the
real world. Electroweak and short distance interactions are well explained by perturbative
expansions in gauge coupling powers. Perturbative calculations, however, cannot
account for the confinement problem which is inherently non perturbative in nature.
The non perturbative region of strongly coupled theories was out of reach for any analytical
calculation since the proposal by Wilson of a regularization on the lattice of
gauge field theories. Soon, in early works of lattice field theory it was realized that
Yang Mills theories could also account for confinement of quarks by a potential linearly
rising with distance. In finite temperature calculations it was also shown that this
linear behavior disappears as some temperature Tc , called deconfinement temperature,
above which quarks are not bounded inside hadrons.
At present time there are no widely accepted explanations from first principles of the
dynamics of confinement. Several mechanisms were proposed to describe confinement
at low temperatures by means of the topological properties of Yang Mills theories. We
shall concentrate on the so called Dual Superconductor Picture which conjectures that
confinement is related to condensation of magnetic charges in analogy with common
superconductors where condensation of electric charges “confines” magnetic monopoles.
We shall propose and test a way to prove its correctness in several gauge theories
(see chapter 3). Although no definitive conclusions can be drawn, we shall show, by
using an operator that detects the condensation of magnetic charges in the vacuum,
that the Dual Superconductor Picture is indeed a proper candidate for the description
of the confinement dynamics. The problem was deeply studied in the last years by
the Pisa group. The confinement by condensation of monopoles was demonstrated
in an U(1) abelian theory both analytically (Frölich and Marchetti) and numerically
(Pisa group). During my PhD we discovered that some of our previous data on non
abelian gauge theories were misinterpreted. In pure non abelian gauge theories, the presence of unphysical bulk transitions spoils the relation of the operator singularities
to a confinement-deconfinement transition. Conversely, similar calculations in theories
with fermions in different representations do not show any signal of bulk transitions
and results are consistent with the Dual Superconductor Picture. We are dedicating
our efforts to clarify this unwelcome behavior of the operator. I will present the first
attempts to redefine the operator in pure gauge theories to circumvent these issues.
The problem of a suitable definition of the operator on the lattice is still open and a
detailed discussion on the subject will be proposed in chapter 3.
If the confinement-deconfinement transition is related to the breaking of some symmetry
of the theory we then expect that a true phase transition takes place. Strictly
speaking, we have explicit symmetries only in the two opposite regions of zero and infinite
quark masses (respectively chiral and center symmetries). We aim at establishing
if, even at finite quark masses, the path from the low temperature region (confined) to
the high temperature region where quarks are free, encounters singularities. A positive
answer demonstrates the non trivial fact this two phases have different symmetries, otherwise
confinement is ambiguously defined. In this respect, the problem of determining
the order of the chiral transition in QCD with two degenerate quarks, a case close to
the physical one, becomes a relevant point (chapter 4). In few words, if the transition
is second order for massless quarks we then expect that it turns into a crossover for
light masses, while if the transition is first order then the non analyticity could survive
in a region of small masses (or beyond). The later possibility could explain naturally
the experimental evidence of free quark suppression in nature. In chapter 4 we shall
address the problem with Finite Size Scaling techniques (chapter 2). By isolating the
dependence on one of the two variables (temperature and bare quark mass) we shall
analyze the volume scaling of thermodynamical quantities like specific heat and chiral
condensate susceptibility. The task of unambiguously determining the order is hard to
accomplish but we shall give some evidences that, despite the common lore, the transition
could be first order, and that surely is not second order in the class predicted by
effective theories.
Summarizing the objectives of this thesis is twofold:
• address the confinement problem by probing the vacuum with a magnetically
charged operator to establish if the dual superconductor picture is a valid picture;
• address the confinement problem by studying the related issue of the order of the transition in two flavors quantum chromodynamics.
43
Morales, Patrícia Soares [UNESP]. "Limite de acoplamento forte da QCD e a interação méson-méson." Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/91868.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0
Previous issue date: 2002-03Bitstream added on 2014-06-13T19:26:30Z : No. of bitstreams: 1
morales_ps_me_ift.pdf: 900348 bytes, checksum: 11b8ab9b4c422ec3a42face91d5074e6 (MD5)O mecanismo de rearranjo de tubos de fluxo predito no limite de acoplamento forte da formulação Hamiltoniana da QCD na rede foi implementado num modelo de quarks constituintes e suas consequências investigadas para o espalhamento méson-méson. O rearranjo de tubos de fluxo leva a efeitos similares aos tradicionais efeitos de troca de quarks com troca de um glúon em interações hádron-hádron. Contudo, enquanto o primeiro está relacionado ao regime de confinamento da QCD, o último está relacionado ao regime de liberdade assintótica desta teoria. Mostra-se aqui que ambos mecanismos levam a resultados qualitativamente similares quando o potencial de rearranjo pode ser escrito como a soma de interações locais quark-quark, antiquark-antiquark e quark-antiquark. Para interações gerais, não locais e de longo alcance, o rearranjo de tubos de fluxo leva a resultados qualitativa e quantitativamente diferentes dos resultados de troca de quarks com troca de um glúon. As consequências disso para a fenomenologia das interações hádron-hádron são discutidas.
The mechanism of link rearrangement predicted in the strong coupling limit of Hamiltonian lattice QCD is implemented in a constituent quark model and its consequences for meson-meson scattering are investigated. Link rearrangement leads to effects similar to the traditional quark exchange with one gluon exchange in hadron-hadron interactions. However while the first is related to the confinement regime of QCD, the latter is related to the asymptotic freedom regime of this theory. It is shown here that both mechanisms lead to identical qualitative results when the rearrangement potential can be written as a sum of local quark-quark, antiqurk-antiquark e quark-antiquark. For general, long-range nonlocal interactions, link rearrangement leads to results qualitative and quantitatively different from those of quark exchange with one gluon exchange. The consequences of this for the phenomenology of hadron-hadron interactions are discussed.
44
Foster, Martyn Stuart. "Adjoint sources, disconnected loops and other fruit of lattice QCD." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366408.
Full text
45
Antunes, Sérgio M. "Estudo de sistemas hadrônicos no limite de acoplamento forte da QCD: simetria quiral a densidades e temperaturas finitas /." São Paulo, 2009. http://hdl.handle.net/11449/132749.
Full textAbstract:
Orientador: Gastão Inácio KreinBanca: Rudnei de Oliveira Ramos
Banca: Heron Carlos de Godói Caldas
Banca: Sérgio Szpigel
Banca: Sandra dos Santos Padula
Resumo: Desenvolvemos um formalismo para estudar a quebra dinâmica da simetria quiral na matéria hadrônica em que os quarks e gluons estão confinados no interior dos hádrons. O formalismo emprega as técnicas tradicionais da teoria quântica de muitos corpos em conjunção com a representação Fock-Tani, em que os estados ligados hadrônicos são descritos em termos de operadores de campos que satisfazem regras de comutação canônicas em um espaço de Fock estendido. Empregamos um modelo de quarks inspirado na Hamiltoniana da QCD no calibre de Coulomb que confina quarks e gluons e realiza a quebra dinâmica da simetria quiral. Resultados numéricos foram obtidos para a equação de gap para os quarks num meio hadrônico formado por nucleons a temperatura zero. Como aplicação do formalismo estimamos os efeitos da densidade bariônica sobre o potencial de interação entre mésons charmosos D com nucleons obtido com a representação Fock-Tani dentro do mesmo modelo de quarks
Abstract: We have developed a formalism to study dynamical chiral symmetry breaking in hadronic matter where quarks and gluons are confined within hadrons. The for- malism employs the traditional techniques of the quantum many body theory in conjunction with the Fock-Tani representation in which the hadronic bound States are described in terms of field operators that satisfy canonical commutation rela- tions in an extended Fock space. We have employed a quark model inspired in the QCD Hamiltonian in Coulomb gauge that confines quarks and gluons and realizes dynamical chiral symmetry breaking. Numerical results are obtained for the gap equation in a hadronic médium formed by nucleons at zero temperature. As an application of the formalism we have estimated the effects of the barionic density on the interaction potential of charmed D mesons with nucleons obtained with the Fock-Tani representation within the the same quark model
Doutor
46
Watson, Peter. "The inclusion of ghosts in Landau gauge Schwinger-Dyson studies of infrared QCD." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4197/.
Full textAbstract:
It is widely believed that Quantum Chromodynamics (QCD) is the theory that describes the strong interaction. In the infrared region of the theory, the perturbative expansion breaks down and so, other techniques must be used. One such technique is the study of the Schwinger-Dyson equations. In this thesis is presented such a study. It is shown that the ghost sector of QCD may be crucial to the understanding of the infrared behaviour. Conventionally, the Slavnov- Taylor identity is used to truncate the Schwinger-Dyson equations but it is found that for the ghost-gluon vertex, such an identity cannot be used in an appropriate manner. In order to extract information, a new technique is presented, based on the powerlaw behaviour of the two-point functions in the infrared. By demanding consistency in the full equations in Landau gauge and multiplicative renormalisability, it is found that in general, the gluon propagator dressing function cannot diverge and the ghost propagator function cannot vanish in the infrared. Further, it is shown that the powerlaw behaviour depends on a certain kinematical limit of only one function connected with the ghost-gluon vertex.
47
Jin, Zhong. "The perturbative and non-perturbative QCD effects in the azimuthal distribution of hadron jets observed in muon deep inelastic scattering /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9724.
Full text
48
Sharkey, Kieran James. "An investigation of the running coupling and meson masses in lattice QCD." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343926.
Full text
49
Gulez, Emel. "B meson semileptonic form factors using unquenched lattice QCD." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155239314.
Full text
50
Joshi, Kiran. "Precision measurements of QCD radiation in top-antitop and Z+jets final states at ATLAS." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/precision-measurements-of-qcd-radiation-in-topantitop-and-zjets-final-states-at-atlas(bc1b9137-f71f-4988-8484-3c604ea2bfff).html.
Full textAbstract:
This thesis presents precision measurements and phenomenological studies of quark and gluon radiation in top-antitop and Z+jets final states. A measurement of top-antitop production with a veto on additional jet activity is performed using 2.1 inverse femtobarn of proton-proton collision data with a centre-of-mass energy of 7 TeV, collected by the ATLAS detector. Jet veto efficiency measurements are performed in several regions of rapidity and corrected for the effects of finite detector resolution and acceptance. A total experimental uncertainty of less than 5% is achieved in all distributions. Two phenomenological studies are performed on the additional quark and gluon radiation produced in association with boosted top-antitop systems. In the first study it is shown how a measurement of the jet veto efficiency can be used to identify the colour of a TeV-scale resonance decaying to top-antitop. The second follow-up study describes how the performance of several top-tagging algorithms is affected by the colour structure of an event. Measurements of the electroweak production of dijets in association with a Z-boson and distributions sensitive to vector boson fusion are performed using 20.3 inverse femtobarn of proton-ptoron collision data collected by ATLAS at 8 TeV. Detector-corrected differential cross sections, and distributions sensitive to radiation produced in addition to the Zjj system, are measured in five fiducial regions with varying sensitivity to the electroweak component of the Zjj cross section. Data are compared to MC predictions and are in reasonable agreement in the majority of cases. The electroweak Zjj cross section is extracted and found to be in good agreement with theory predictions. Limits are also placed on anomalous triple gauge couplings. The commissioning of an event filter isolated muon trigger is also presented. The trigger became one of the primary muon triggers used during the 2012 data taking.