No description available.

Die Berechnung von Tensorintegralen ist eines der komplizierteren Probleme bei der Berechnung von Einschleifen-Feynmandiagrammen. In dieser Arbeit wird die Computerprogrammbibliothek PJFry entwickelt, mit der Tensorintegrale mit bis zu fünf äusseren Beinen und unter Zugrundelegung beliebiger Kinematik numerisch ausgewertet werden können. Im Programm PJFry sind Algorithmen implementiert, mit denen bei der Reduktion von Pentagon-Tensoren inverse Potenzen der Gramdeterminanten vermieden werden können. Gramdeterminanten der Boxdiagramme werden unter Verwendung von Rekursionsrelationen mit variabler Raum-Zeit-Dimension in einem Satz neuer Basisintegrale isoliert. Die neuen Basisintegrale werden ebenfalls durch Rekursionsrelationen mit variabler Raum-Zeit-Dimension oder durch Entwicklung in kleinen Gramdeterminanten ausgewertet. Die Konvergenz letzterer wird durch Padé-Extrapolation erheblich beschleunigt. Ein Cache-System erlaubt die mehrfache Verwendung von numerischen Bausteinen und erhöht zusätzlich die Effizienz des Programmpakets. Ausser ausführlichen Tests von Struktur und Genauigkeit der Algorithmen wird eine nichtriviale Beispielanwendung ausgearbeitet und mit dem Programm NGluon verglichen: die Berechnung von fünf-Gluon-Helizitätsamplituden. Schließlich werden die virtuellen Einschleifenkorrekturen zur Myonpaarproduktion mit Emission energiereicher ("harter") Photonen berechnet. Die Methode wird erläutert, wie auch Renormierung und Behandlung der Polstruktur in dimensionaler Regularisierung. Numerische Vorhersagen für differentielle Wirkungsquerschnitte werden berechnet, unter Zugrundelegung der kinematischen Situationen, wie sie bei den Detektoren KLOE (DAFNE, Frascati) und BaBar (SLAC) typisch sind. / In this thesis we discuss the problem of evaluation of tensor integrals appearing in a typical one-loop Feynman diagram calculation. We present a computer library for the numerical evaluation of tensor integrals with up to 5 legs and arbitrary kinematics. The code implements algorithms based on the formalism which avoids the appearance of inverse Gram determinants in the reduction of pentagon diagrams. The Gram determinants of box integrals are isolated in the set of new basis integrals by using dimensional recurrence relations. These integrals are then evaluated by dimensional recurrence or expansion in small Gram determinant, which is improved by Padé extrapolation. A cache system allows reuse of identical building blocks and increases the efficiency. After describing the cross checks and accuracy tests, we show a sample application to the evaluation of five gluon helicity amplitudes, which is compared with the output of the program NGluon. In the last part the program is applied to the calculation of the one-loop virtual corrections to the muon pair production with hard photon emission. The computation method is explained, followed by a discussion of renormalization and pole structure. Finally, we present numerical results for differential cross sections with kinematics of the KLOE and BaBar detectors.

Hadronic collider experiments have played a major role in particle physics phenomenology over the last few decades. Data recorded at the Tevatron at Fermilab is still of interest, and its successor, the Large Hadron Collider (LHC) at CERN, has recently announced the discovery of a particle consistent with the Standard Model Higgs boson. Hadronic colliders look set to guide the field for the next fifteen years or more, with the discovery of more particles anticipated. The discovery and detailed study of new particles relies crucially on the availability of high-precision theoretical predictions for both the signal and background processes. This requires observables to be calculated to next-to-leading order (NLO) in perturbative quantum chromodynamics (QCD). Many hadroproduction processes of interest contain multiple particles in the final state. Until recently, this caused a bottleneck in NLO QCD calculations, due to the difficulty in calculating one-loop corrections to processes involving three or more final state particles. Spectacular developments in on-shell methods over the last six years have made these calculations feasible, allowing highly accurate predictions for final state observables at the Tevatron and LHC. A particular realisation of on-shell methods, generalised unitarity, is used to compute the NLO QCD cross-sections and distributions for two processes: the hadroproduction of W⁺ W^-jj, and the hadroproduction of W⁺ W^-jj. The NLO corrections to both processes serve to reduce the scale dependence of the results significantly, while having a moderate effect on the central scale choice cross-sections, and leaving the shapes of the kinematic distributions mostly unchanged. Additionally, the gluon fusion contribution to the next-to-next-to-leading order (NNLO) QCD corrections to W⁺ W^-j productions are studied. These contributions are found to be highly depen- dent on the kinematic cuts used. For cuts used in Higgs searches, the gluon fusion effect can be as large as the NLO scale uncertainty, and should not be neglected. All of the higher-order QCD corrections increase the accuracy and reliability of the theoretical predictions at hadronic colliders.

Cette thèse a pour objet l'étude de divers sujets liés à la physique du LHC et à ses prédictions. Nous nous sommes dans un premier temps intéressés à la recherche au LHC d'un boson de Higgs léger ($M_H\simeq 120$ GeV) et boosté ($p_{t,H}>200$ GeV) dans le canal $pp\rightarrow WH$ et $pp\rightarrow ZH$ avec $H\rightarrow b\bar b$. Nous avons montré comment, à partir d'une analyse de la sous-structure des jets en deux étapes respectivement appelées ``mass-drop'' et ``filtering'', il est possible de réduire de manière significative les divers backgrounds (mass-drop) et d'améliorer la résolution en masse lors de la reconstruction du Higgs (filtering). Cela nous a permis de rendre prometteur ce canal de recherche au LHC, longtemps considéré comme trop difficile. A partir de là nous nous sommes concentrés plus particulièrement sur la procédure du ``filtering'', qui permet de supprimer autant que possible l'effet du bruit de fond diffus que constituent l'underlying-event et le pile-up, en majeur partie responsable de la dégradation de la résolution. Nous avons optimisé ses paramètres à partir d'une analyse semi-analytique, ce qui nous a conduits à l'étude de la structure des ``non-global'' logarithms qui interviennent lors du calcul de la distribution en masse du Higgs. Finalement, nous nous sommes penchés sur les processus dont la série perturbative présente une mauvaise convergence au next-to-leading (NLO) order pour certaines observables, une caractéristique que nous avions en particulier remarquée pour les processus Z+jet et W+jet à grand $p_t$ lors de notre première étude sur le Higgs. Cet aspect est important car cette mauvaise convergence induit une perte de confiance sur les prédictions résultant des calculs perturbatifs. Il devient donc nécessaire d'examiner les ordres supérieurs, ce que permet de façon approximative un nouvel outil que nous avons élaboré, appelé ``LoopSim'', qui combine divers ordres de la théorie des perturbations de manière à annuler les divergences molles et collinéaires qui apparaissent inévitablement.

In this study, two series of polymers based on benzobisthiazole were synthesized. The poly(benzobisthiazoles) (PBTs) have been synthesized by the solution polycondensation of 2,5-diamino-1,4-benzenedithiol in poly(phosphoric acid)s (PPA). The diacids used were systematically varied to find the best for the solubilization of the aromatic heterocyclic rigid-rod polymers. The role of PPA is identified and the effects of phosphorous pentoxide and water on PBT during polycondensation are discussed. Polymer properties such as the inherent viscosity, decomposition temperature are correlated to systematically varied diacids. Finally, the effect of diacid architecture on the synthesis and microstructure of PBT is studied. The results are further discussed in terms of resonance, symmetry, and solubilization of the diacids. Next, we extend the rigidity and resonance of benzobisthiazole for the application as second-order nonlinear optics. Novel nonlinear optical (NLO) polyimides containing benzobisthiazole chromophores have been synthesized. The soluble polyimides containing different ratios of carboxylic acids (COOH) were first prepared and the precursors of NLO chromophores reacted with those carboxylic acids, followed by the benzobisthiazole derived chromophores synthesized at 300 oC under vaccum. The formation of benzobisthiazole was evidenced by FTIR and UV-vis spectra in combination with the analysis of model polyimides. The excellent thermal properties of those NLO polyimides were examined by TGA and TMA. PI-1 shows thermal decomposition temperature as high as 554 oC at 10 wt % loss and a Tg of 324 oC. The amorphous morphology of those polyimides was verified by XRD traces and some ordered alignments were found, due to the rigidity of the benzobisthiazole derivatize chromophores. The electrooptic coefficient of PI-1 (r33 = 5.3 pm/V) was obtained.

O trabalho apresenta a síntese e a caracterização de novos compostos heterocíclicos benzazólicos dos tipos 2-(4’-aminofenil)-6-nitrobenzazóis fluorescentes por apresentar provável transferência de carga intramolecular no estado excitado (ICT) e iminas aromáticas basedas nos compostos 2-(4’-amino-2’- hidroxifenil)-6-nitrobenzazóis fluorescentes devido a mecanismo de transferência protônica intramolecular no estado excitado (ESIPT). Estes compostos foram caracterizados por espectroscopia de absorção na região do Infravermelho, ressonância magnética nuclear de hidrogênio (1H-RMN). Foram realizados estudos fotofísicos através das espectroscopia de absorção na região do ultravioleta-visível e de emissão de fluorescência, determinando assim, os prováveis estados eletrônicos excitados em solventes polares e apolares. / This work presents the synthesis and characterization of new fluorescent heterocyclic derivatives based on 2-(4'-aminophenyl)-6-nitrobenzazoles, as well as aromatic imines based on 2-(4'-amino-2'-hydroxyphenyl)-6-nitrobenzazoles. These molecules are photoactive due to an intramolecular proton transfer in the excited state (ESIPT) or a intramolecular charge transfer (ICT) mechanism. These compounds were characterized by infrared spectroscopy and nuclear magnetic resonance 1H-NMR. Photophysical studies were performed using the absorption spectroscopy in the ultraviolet-visible and fluorescence emission, thereby determining the excited electronic states in polar and nonpolar solvents.

O trabalho apresenta a síntese e a caracterização de novos compostos heterocíclicos benzazólicos dos tipos 2-(4’-aminofenil)-6-nitrobenzazóis fluorescentes por apresentar provável transferência de carga intramolecular no estado excitado (ICT) e iminas aromáticas basedas nos compostos 2-(4’-amino-2’- hidroxifenil)-6-nitrobenzazóis fluorescentes devido a mecanismo de transferência protônica intramolecular no estado excitado (ESIPT). Estes compostos foram caracterizados por espectroscopia de absorção na região do Infravermelho, ressonância magnética nuclear de hidrogênio (1H-RMN). Foram realizados estudos fotofísicos através das espectroscopia de absorção na região do ultravioleta-visível e de emissão de fluorescência, determinando assim, os prováveis estados eletrônicos excitados em solventes polares e apolares. / This work presents the synthesis and characterization of new fluorescent heterocyclic derivatives based on 2-(4'-aminophenyl)-6-nitrobenzazoles, as well as aromatic imines based on 2-(4'-amino-2'-hydroxyphenyl)-6-nitrobenzazoles. These molecules are photoactive due to an intramolecular proton transfer in the excited state (ESIPT) or a intramolecular charge transfer (ICT) mechanism. These compounds were characterized by infrared spectroscopy and nuclear magnetic resonance 1H-NMR. Photophysical studies were performed using the absorption spectroscopy in the ultraviolet-visible and fluorescence emission, thereby determining the excited electronic states in polar and nonpolar solvents.

O trabalho apresenta a síntese e a caracterização de novos compostos heterocíclicos benzazólicos dos tipos 2-(4’-aminofenil)-6-nitrobenzazóis fluorescentes por apresentar provável transferência de carga intramolecular no estado excitado (ICT) e iminas aromáticas basedas nos compostos 2-(4’-amino-2’- hidroxifenil)-6-nitrobenzazóis fluorescentes devido a mecanismo de transferência protônica intramolecular no estado excitado (ESIPT). Estes compostos foram caracterizados por espectroscopia de absorção na região do Infravermelho, ressonância magnética nuclear de hidrogênio (1H-RMN). Foram realizados estudos fotofísicos através das espectroscopia de absorção na região do ultravioleta-visível e de emissão de fluorescência, determinando assim, os prováveis estados eletrônicos excitados em solventes polares e apolares. / This work presents the synthesis and characterization of new fluorescent heterocyclic derivatives based on 2-(4'-aminophenyl)-6-nitrobenzazoles, as well as aromatic imines based on 2-(4'-amino-2'-hydroxyphenyl)-6-nitrobenzazoles. These molecules are photoactive due to an intramolecular proton transfer in the excited state (ESIPT) or a intramolecular charge transfer (ICT) mechanism. These compounds were characterized by infrared spectroscopy and nuclear magnetic resonance 1H-NMR. Photophysical studies were performed using the absorption spectroscopy in the ultraviolet-visible and fluorescence emission, thereby determining the excited electronic states in polar and nonpolar solvents.

Title: Molecular crystals for NLO applications - compounds of 1H-pyrazole-carboxamidine Author: Bc. Soňa Kohúteková Department: Department of Inorganic Chemistry Supervisor: prof. RNDr. Ivan Němec, Ph.D. Abstract: The aim of this diploma thesis is preparation and characterisation of novel compounds of 1H-pyrazole-carboxamidine in consideration of their potential application in the field of nonlinear optics. This thesis is focused on preparation of crystalline salts or adducts combining 1H-pyrazole-carboxamidine with selected inorganic and organic acids. Prepared materials were characterised mainly by the means of vibrational spectroscopy and X-ray diffraction analysis. Quantum-chemical calculations were used for a prediction of nonlinear optical properties as well as for interpretation of measured vibrational spectra. Four different approaches of calculations were used for an optimisation of computing time together with accuracy of the fit of calculated and measured spectra. Finally, measurements of second harmonic generation efficiency of two powder samples with non-centrosymmetric crystal structures were performed. Key words: NLO, vibrational spectroscopy, crystal structure, quantum-chemical calculations

No description available.