Dissertationen zum Thema „Calculs à deux boucles“
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Barrios, Nahuel. „Yang-Mills and Quantum Chromodynamics correlation functions from the Curci-Ferrari model at two-loop accuracy“. Electronic Thesis or Diss., Institut polytechnique de Paris, 2022. http://www.theses.fr/2022IPPAX081.
Der volle Inhalt der QuelleQuantum Chromodynamics (QCD) is a well established gauge theory which describes the dynamics of quarks and gluons. At the analytical level, physical observables can be computed only after the gauge is fixed. The textbook procedure to do so is the Faddeev-Popov (FP) method, which introduces, as a byproduct, auxiliary non-physical fields known as ghosts. Moreover, the QCD gauge coupling becomes small at very high momenta, making of perturbation theory (PT) a suitable calculation tool within that region of momenta. The combination of the FP theory and PT has turned out to be extremely useful and has been tested experimentally in many occasions. However, in the opposite momentum range, the FP method is no longer fully valid due to the presence of Gribov copies. Consequently, in order to access QCD in the infrared, new approaches are needed.This thesis is devoted to one of such approaches: the Curci-Ferrari (CF) model in Landau gauge. It consists in a simple gluon mass extension of the FP theory. Its main motivation comes from the lattice simulations for correlation functions in the Landau gauge, which clearly indicate that the gluon acquire a mass in the deep infrared. In addition to this striking phenomenon, the lattice simulations feature a gauge coupling compatible with a perturbative analysis for the whole range of momenta, at least in the pure gauge - or Yang-Mills (YM) - sector. Thus, with the purpose of testing the model, several two- and three-point correlation functions have been perturbatively evaluated at one-loop order. In general terms, the results show a very good agreement with the lattice data. More recently, the two-point functions from the pure YM theory were evaluated at two-loop order, improving the agreement to lattice data. The goal of this thesis is to extend the two-loop calculations to other correlation functions. This is a way of further testing the perturbative use of the model as well as to clarify its limits.In the case of pure YM theory, we evaluate the ghost-antighost-gluon vertex and the three-gluon vertex in a particular kinematical configuration in four dimensions, for the SU(2) and SU(3) gauge groups. Both quantities emerge as a pure prediction of the CF model, since its two free parameters are determined by fitting the two-point functions. Broadly speaking, the predicted vertices are able to improve the agreement with their numerical counterparts in comparison with the one-loop correction. We also investigate the renormalization scheme dependence of our results, which shows consistency with the perturbative approach. As for the three-gluon vertex, the calculation allows us in particular to gain insight on the zero-crossing as well as to test an exact prediction for the leading behavior in the infrared.We end this investigation by computing the ghost, gluon and quark two-point functions in QCD, with two degenerate quark flavors. We fit them to available lattice data. Our evaluation is consistent with such data in all the cases, except for the quark mass function for light quarks. The result is particularly relevant for the quark dressing function, since the CF model is unable to reproduce the lattice data at one-loop order. This discrepancy is corrected by the two-loop evaluation, which agrees with the data both at a qualitative and quantitative level
Ikhlef, Yacine. „Résultats exacts sur les modèles de boucles en deux dimensions“. Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00268765.
Der volle Inhalt der QuelleMahmoudi, Farvah. „Chromodynamique quantique aux collisionneurs hadroniques : vers une automatisation du calcul des processus multi-particules à l'ordre d'une boucle : application à la production de deux photons et un jet“. Chambéry, 2004. http://www.theses.fr/2004CHAMS013.
Der volle Inhalt der QuelleThe future CERN collider (LHC) bas a fantastic potential of discovery, provided QCD can be quantitatively predicted. To do so, it is necessary to work at NLO approximation in order to reduce the dependence of the cross-section on the non-physical scales. To obtain results in this approximation, one has to calculate the cross-sections of the partonic subprocesses contributing to the studied reaction at the lowest order, and also the virtual corrections (loop corrections) and the real corrections. The calculation of the virtual corrections remains very complicated if the number of external particles is greater than four or if the external (internal) particles are massive. Ln this thesis, an automatic method which enables to calculate one loop diagrams with five external legs and which can be generalized to the case of massive particles is presented. Ln a first part, we describe different tools and methods necessary to such calculations. We then apply them to the calculation of the (gluon + gluon -> photon + photon + gluon) reaction, which interests the ATLAS and CMS experimentalists as the background for the Higgs boson search. We also give the explicit result for this amplitude for each helicity configuration in a compact form and a clearly gauge invariant representation. We finally present a phenomenological study of this reaction
Marx, Alain. „Deux étapes majeures pour le développement du code XTOR : parallélisation poussée et géométrie à frontière libre“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX095/document.
Der volle Inhalt der QuelleThe XTOR-2F code simulates the 3D dynamics of full bi-fluid MHD instabilities in tokamak plasmas.The first part of the thesis was dedicated to the parallelisation of XTOR-2F code. The code has been parallelised significantly despite the numerical profile of the problem solved, i.e. a discretisation with pseudo-spectral representations in all angular directions, the stiffness of the two-fluid stability problem in tokamaks, and the use of a direct LU decomposition to invert the physical pre-conditioner. The execution time of the parallelised version is an order of magnitude smaller than the sequential one for low-resolution cases, with an increasing speedup when the discretisation mesh is refined. Moreover, it allows to perform simulations with higher resolutions, previously forbidden because of memory limitations.The second part of the thesis was dedicated to the development of free boundary condition. The original fixed boundary computational domain of the code was generalised to a free-boundary one, thus approaching closely the geometry of today’s and future large experimental devices. The initial conditions are given by the CHEASE equilibrium code inside the plasma. Outside the plasma, fitting the magnetic potential at the CHEASE computation domain boundary with a set of external poloidal magnetic coils extends the solution. The boundary conditions use Green functions to construct a response matrix matching the normal and tangential components of the outside magnetic field with the inside solution. A thin resistive wall can be added to the computational domain. This new numerical setup generalises the investigation field from internal MHD instabilities towards external instabilities. The code linear behaviour is validated with two families of instabilities, n = 0 axisymmetric modes and n = 1/m = 2 external kinks. In order to validate the nonlinear behaviour, nonlinear resistive MHD simulations of tearing modes at zero beta evolving to a stationary state have been performed
Poidevin, Corentin. „Calculs et analyses théoriques d'états excités optiques et magnétiques en série carbo-mère quadrupolaire et organométallique dipolaire“. Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30250/document.
Der volle Inhalt der QuelleThe first chapter of this thesis reports on the theoretical study of linear and nonlinear optical properties of organic and organometallic experimental targets developed in the group, especially quadrupolar carbo-benzene derivatives. Standard methods for the calculation and the analysis of excited states are presented first, as well as two theoretical tools developed in this work addressing: (i) the charge transfer character in terms of "hole" and "particle" densities and (ii) the visualization of the transition dipole moment from the transition density truncated to the main mono-excitations (TTD). The first excited states of the chromophores calculated at the TD-DFT level, and at the CAS- PT2 level for a few model chromophores, are then analyzed. The one-photon UV-visible absorption spectra of carbo-benzene derivatives fit with the Gouterman model originally proposed for porphyrins, where the four first excited states involve linear combinations of mono-excitations of the same four frontier molecular orbitals. The relative intensities of the absorption bands are analyzed from the transition dipole moments calculated from the TTDs. An analogy between porphyrins and carbo-benzenes is then argued. The "hole" and "particle" densities are used to study the charge transfer character of the first excited states of palladium(II) complexes, built from electron-rich carbon ligands and electron-poor phosphorus ligands. The two-photon absorption (TPA) efficiency, a third order nonlinear optical property, is then studied. For each two-photon allowed excited state, a TPA cross-section (sTPA) has been calculated, from the contribution of all possible intermediate excited states, using the "sum-over-state" (SOS) method. Most of the carbo-benzene derivatives fit with the "three level model", with a major contribution of one intermediate state to the TPA cross-section. sTPA ˜ (µ0i2*µif2)/?E2, where ?E is the difference between the energy of the intermediate state (one-photon allowed) and half the energy of the final state (two- photon allowed). The TPA efficiency can thus be analyzed from the transition dipole moments (µ0i and µif), which can be calculated from the TTDs, and the energies of the two transitions. In the second chapter, the stability of organic di- or poly-radicals was studied in collaboration with Jean-Paul Malrieu, Georges Trinquier and Esmail Alikhani. The di- or poly-radical open-shell singlet spin state of carbo-benzenes of first, second and third generation, and of related acyclic motifs, is first studied using broken-symmetry calculations. The spin-decontamination of the MS = 0 broken-symmetry solution is then performed either (i) at constant geometry according to the procedure of Labanowski et al. or (ii) following the "recipe" of Malrieu et al., yielding the optimized geometry of the open-shell singlet spin state. The stability of the latter for oligoacetylenic systems of the carbo-mer type has been compared to the one of parent oligobenzenic systems. A structural analysis of the results is discussed in terms of "spin insulating moieties" and "spin stabilizing moieties". The former may be related to aromaticity (1,4-phenylene > 1,2-ethynylene), while the latter may be related to spin delocalization. The trialkynylmethyle radical (TAM) is suggested as a particularly efficient spin stabilizing pattern. On the basis of these results, several carbo-meric synthesis targets are suggested
Allemand, Jean Francois. „Quelques expériences entre physique, chimie, biologie :formations de boucles dans l'ADN, moteurs moléculaires etségrégation chromosomique, excitation biphotonique,spectroscopie de corrélation de fluorescence“. Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2006. http://tel.archives-ouvertes.fr/tel-00141893.
Der volle Inhalt der Quellemicromanipulations de molécules d'ADN uniques avec des pinces magnétiques
pour étudier la cinétique et thermodynamique de formation de boucles
sur l'ADN par le répresseur GalR. Nous avons également étudié les propriétés
de la translocase à ADN FtsK impliquée dans la ségrégation des chromosomes
chez E. coli. Dans une seconde partie nous avons mis en place différentes
expériences utilisant l'excitation biphotonique. Tout d'abord nous
avons construit un dispositif pour mesurer les sections efficaces d'absorption
à deux photons de molécules synthétisées au laboratoire.Nous avons ensuite
mis en place la technique de corrélation de fluctuations de fluorescence pour
mesurer des coefficients de diffusion et des constantes cinétiques.
Rouimi, Patrick. „Contribution à l'étude structurale et fonctionnelle de deux protéines du pancréas exocrine la protéine des calculs pancréatiques humains, la lipase pancréatique de porc /“. Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37609524x.
Der volle Inhalt der QuelleHilico, Laurent. „Mesures de fréquences et calculs de haute précision en physique atomique et moléculaire“. Habilitation à diriger des recherches, Université d'Evry-Val d'Essonne, 2002. http://tel.archives-ouvertes.fr/tel-00001922.
Der volle Inhalt der QuelleRouimi, Patrick. „Contribution à l'étude structurale et fonctionnelle de deux protéines du pancréas exocrine : 1. La protéine des calculs pancréatiques humains. 2. La lipase pancréatique du porc“. Aix-Marseille 2, 1987. http://www.theses.fr/1987AIX22096.
Der volle Inhalt der QuelleSimon, Aude. „Activation du méthane par deux cations métalliques de la troisième série, W+ et Ta+ : synergie entre expériences en phase gazeuse et calculs de chimie quantique“. Paris 11, 2002. http://www.theses.fr/2002PA112143.
Der volle Inhalt der QuelleThe present thesis aims at characterizing the chemistry of ligated M+ using both quantum chemistry and FT-ICR mass spectrometry. Third row transition metal cations M+ are the most reactive towards methane, and in the case of M=Ta and W, a sequence of four successive methane activation steps is observed in an FT-ICR, which is evidenced by the observation of the four intermediates MCH2+, MC2H4+, MC3H6+ and MC4H8+. These have been characterized by UV-Visible photofragmentation for M=Ta and W. In the case of M=W, the photofragmentation thresholds provide thermodynamic informations on the intermediates. In the case of M=Ta, although the photofragmentation pathways are identical, the associated thresholds are much larger than in the case of M=W. We show that this particular behavior is related to the electronic spectrum of the intermediates, thus allowing for the prediction of their structure. A mechanism is proposed for the two first steps of the sequential activation of methane by M+ (M=Ta, W). Whereas the first step is kinetically controlled by the oxidative addition of M+ into the CH bond, three alternative activation mechanisms are proposed for the following steps. The activation of the first methane molecule leads to the competitive formation of a carbene MCH2+ and hydridocarbyne HMCH+. Activation of methane by MCH2+ can either proceed through sigma/pi metathesis, or the oxidative addition can be assisted by a coordination change of the carbene ligand. A combination of experimental and theoretical results gives evidence that a sigma-bond metathesis mechanism, allowed by a M-hydride bond, is at the origin of the third and fourth activation. Finally, the first example of infrared characterization of ions in an FT-ICR is presented in the case of Fe+-hydrocarbon complexes. This study demonstrates the feasibility of the photofragmentation induced by infrared multiphoton absorption and thus opens the field of a direct characterization of mass selected intermediates by infrared
Svirina, Kseniia. „Les équations de groupe de renormalisation à deux boucles pour les théories de jauge générales et quelques aspects de la phénoménologie du Higgs dans des modèles au-delà du MS“. Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY021.
Der volle Inhalt der QuelleWe revisit the renormalisation group equations (RGE) for general renormalisable gaugetheories at one- and two-loop accuracy. We identify and correct various mistakes inthe literature for the beta functions for both dimensionless and dimensionful Lagrangianparameters. The discrepancies arise form the assumption of a diagonal wave-functionrenormalisation in the literature, which is not appropriate for models with mixing in thescalar sector, and due to inaccurate use of the dummy field method employed in the literature for the derivation of the beta functions for dimensionful parameters. We performan independent cross-check using well-tested supersymmetric RGEs which confirms ourresults. The numerical impact of the changes in the beta function for the fermion mass termsis illustrated using a toy model with a heavy vector-like fermion pair coupled to a scalargauge singlet. Unsurprisingly, the correction to the running of the fermion mass becomessizeable for large Yukawa couplings of the order of O(1). Furthermore, we demonstratethe importance of the correction to the beta functions of the scalar quartic couplings using a general type-III Two-Higgs-Doublet-Model. We also provide a detailed pedagogicdiscussion of the dummy field method and summarize all the correct expressions for thebeta functions in one place.As an independent part of the reserach, we study the BSM Higgs physics in theRandall-Sundrum (RS) model with one extra dimension, predicting a new scalar particle, the radion, the remarkable similarity of which to the Higgs boson has been noticed. The model is implemented in the FeynRules package for the derivation of theFeynman rules, which is helpful for the future study of the collider phenomenology of theRS model with MadGraph, in particular, the scalar pair production and Higgs couplingmodifications
Le, Bigot Eric-Olivier. „QED dans les ions à un et deux électrons : états très excités ou quasi-dégénérés“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00006418.
Der volle Inhalt der Quellenumériques de contributions de l'électrodynamique quantique (QED) aux
niveaux d'énergie des ions à un et deux électrons.
Nous donnons tout d'abord un aperçu des mesures de niveaux d'énergie
dans les systèmes simples formés d'un noyau et de quelques électrons
(en nous concentrant sur l'hydrogène, les ions hydrogénoïdes, l'hélium
et les ions héliumoïdes, y compris très chargés). De tels niveaux
permettent entre autres des mesures très précises de constantes
fondamentales (comme par exemple la constante de structure
fine alpha ou le Rydberg).
Nous faisons le point sur une méthode d'évaluation formelle des
niveaux d'énergie prédits par QED : la méthode "de la fonction de
Green à deux temps", et nous en donnons une présentation très
détaillée. Cette méthode permet d'obtenir de QED les énergies de
niveaux atomiques, y compris lorsque ceux-ci sont dégénérés ou
quasi-dégénérés (dans l'approximation d'électrons ne subissant que
l'attraction du noyau) --- ce qu'il n'est possible de faire qu'avec
une seule autre méthode, très récente. Nous montrons qu'il est
possible de résoudre les difficultés de principe que pose la méthode
de la fonction de Green à deux temps, grâce à une étude (restreinte au
problème considéré) du lien entre les propriétés analytiques d'une
fonction méromorphe et de son développement perturbatif. Afin de
pouvoir utiliser de façon pratique la méthode de la fonction de Green
à deux temps pour l'obtention des niveaux d'énergie prédits par QED,
nous introduisons de plus la méthode graphique "de la particule
fantôme", qui permet de calculer systématiquement un hamiltonien
effectif pour les niveaux considérés. Enfin, nous présentons un calcul
détaillé d'une contribution (la "self énergie écrantée") au
hamiltonien effectif, qui montre que la méthode de la particule
fantôme peut être appliquée de façon générale à l'évaluation des
déplacements en énergie dûs à n'importe quel diagramme de Feynman.
Enfin, nous étendons par des formules analytiques la méthode
actuellement la plus précise de calcul du déplacement le plus
important de QED (la self énergie), dans l'hydrogène et les ions
hydrogénoïdes. Cette méthode numérique permet d'obtenir le déplacement
de self énergie de niveaux de moment cinétique quelconque (elle était
auparavant restreinte à j <= 3/2). Nous montrons qu'il est ainsi
possible de calculer numériquement le déplacement de self énergie de
nombreux niveaux excités, avec une très bonne précision.
Bukhanko, Valerii. „Libération du monoxyde d'azote induite par deux photons à partir de complexes ruthénium-nitrosyle contenant des ligands de capacités push-pull différentes“. Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30137/document.
Der volle Inhalt der QuelleThe work "Two-photon induced photorelease of nitric oxide from ruthenium-nitrosyl complexes containing ligands of various push-pull capabilities" was devoted to the revealing of main factors that determine the efficiency of ruthenium-nitrosyl complexes in two-photon absorption (TPA) and the improvement of TPA cross-section through modification of the ligands nature and their structure. Starting from complexes previously obtained by the research group of Prof. I. Malfant, we have modified their structure in several directions. It was shown that substitution of monodentate ligands by 2,2'-bipyridine in ruthenium complexes with nitrosyl ligands leads to a slight increase of their TPA cross- section, however this modification decreases the quantum yield of the nitric oxide photo release. Synthetic part of the work was mainly aimed at the modification of the ligand
Kerbouai, Hamza. „Modélisation, dimensionnement et optimisation d'un capteur hybride pour la détection des deux roues motorisées dans le trafic routier“. Thesis, Belfort-Montbéliard, 2015. http://www.theses.fr/2015BELF0260/document.
Der volle Inhalt der QuelleFor several years the road safety numbers show the need to develop a technological tool that aims to know thepowered two wheelers vehicles behavior (2PW) to improve their security. From this problematic arise our researchworks that come under the project METRAMOTO (Powered two wheelers traffic measurement for road safety andrisks assessment). The main objective is modeling, sizing and optimization of an hybrid sensor consisted ofelectromagnetic loops and piezoelectric shock sensors. The idea is to use electromagnetic loops to discriminate the2PW presence from the other vehicles, combined with piezoelectric segments to detect the shocks produced by thevehicles wheels passage, all associated with a management algorithm and data processing. Today the sizing of thedetection systems based on electromagnetic loops or piezoelectric cables is done experimentally on controlled sitesusing several vehicles types. This technique requires significant test series which are costly and dangerous. Thisstudy aims to modeling the different interactions between the studied sensor and vehicles in order to its sizing.Electromagnetic and electromechanical models are developed to describe the different interactions that take placebetween electromagnetic loops on the one hand, between electromagnetic loops and vehicles on the other handand those between vehicle wheels and piezoelectric cable. On the basis of established models, a general approachis elaborated driving to sizing the hybrid sensor for any given road. We are also interested to the data processingcoming from the hybrid sensor for which we propose an approach to identifying the different vehicle categoriesincluding the 2PW. Two sensor configurations for two different roads are then proposed. They are associated atdata processing algorithms allowing the acquisition of loops and cables signals, the distinction between the differentvehicles classes, the estimation of the vehicles positions on the road and the measuring of their speed
Tran, Ngoc Tien Dung. „Transport de solutés dans un milieu à double-porosité non saturé. Modélisation par homogénéisation et applications“. Phd thesis, Grenoble 1, 2008. http://www.theses.fr/2008GRE10097.
Der volle Inhalt der QuelleThis Ph. D thesis presents the development of the solute transport models in unsaturated double-porosity medium, by using the asymptotic homogenization method. The obtained macroscopic models concern diffusion, diffusion-convection and dispersion-convection, according to the transport regime which is characterized by the non-dimensional numbers. The models consist of two coupled equations that show the local non-equilibrium of concentrations. The double-porosity transport models were numerically implemented using the code COMSOL Multiphysics (finite elements method), and compared with the solution of the same problem at the fine scale. The implementation allows solving the coupled equations in the macro- and micro-porosity domains (two-scale computations). The calculations of the dispersion tensor as a solution of the local boundary value problems, were also conducted. It was shown that the dispersivity depends on the saturation, the physical properties of the macro-porosity domain and the internal structure of the double-porosity medium. Finally, two series of experiments were performed on a physical model of double-porosity that is composed of a periodic assemblage of sintered clay spheres in Hostun sand HN38. The first experiment was a drainage experiment, which was conducted in order to validate the unsaturated flow model. The second series was a dispersion experiment in permanent unsaturated water flow condition (water content measured by gamma ray attenuation technique). A good agreement between the numerical simulations and the experimental observations allows the validation of the developed models
Tran, Ngoc Tien Dung. „Transport de solutés dans un milieu à double-porosité non saturé. Modélisation par homogénéisation et applications“. Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00327123.
Der volle Inhalt der QuelleMoreau, Grégory. „Étude phénoménologique des interactions violant la symétrie de R-parité dans les théories supersymétriques“. Phd thesis, Université Paris-Diderot - Paris VII, 2000. http://tel.archives-ouvertes.fr/tel-00000821.
Der volle Inhalt der QuelleKarr, Jean-Philippe. „Optique quantique dans les microcavités semi-conductrices. Spectroscopie de l'ion moléculaire H2+“. Habilitation à diriger des recherches, Université d'Evry-Val d'Essonne, 2008. http://tel.archives-ouvertes.fr/tel-00347825.
Der volle Inhalt der QuelleJ'aborde dans la deuxième partie mes activités théorique et expérimentale autour de la spectroscopie de l'ion H2+. Le but de l'expérience, qui a débuté en 2003 à l'université d'Evry, est de mesurer la fréquence d'une transition vibrationnelle à deux photons sans effet Doppler, et de la comparer à des prédictions théoriques précises pour en déduire une nouvelle détermination du rapport mp/me. Je décris les progrès des calculs de haute précision sur l'ion H2+ (niveaux d'énergie non relativistes, structure hyperfine), ainsi que le dispositif expérimental mis en place et les perspectives de l'expérience.
Mahmoudi, Farvah. „Chromodynamique Quantique aux collisionneurs hadroniques : Vers une automatisation du calcul des processus multi-particules à l'ordre d'une boucle. Application à la production de deux photons et d'un jet“. Phd thesis, 2004. http://tel.archives-ouvertes.fr/tel-00006725.
Der volle Inhalt der QuelleDans cette thèse est proposée une méthode automatique pour effectuer les calculs à une boucle et à cinq pattes, et qui peut être généralisée aux cas de particules massives.
Dans une première partie, nous décrirons divers outils et méthodes nécessaires à de tels calculs. Nous les appliquerons ensuite au calcul de la réaction (gluon + gluon -> photon + photon + gluon), qui intéresse les expérimentateurs des expériences ATLAS et CMS comme bruit de fond à la recherche du Higgs, notamment pour décrire correctement la queue de la distribution transverse du boson de Higgs. Sera alors présenté le résultat explicite de cette amplitude pour chaque configuration d'hélicités sous une forme compacte et une représentation clairement invariante de jauge. Nous terminerons par une étude phénoménologique de cette réaction.