Orientador: Adriano A. Natale / Banca: Paulo Sérgio Rodrigues da Silva / Banca: Carlos Ourívio Escobar / Banca: Vicente Pleitez / Banca: Juan Carlos Montero Garcia / Resumo: O mecanismo de Higgs baseado na existência de um bóson escalar fundamental apresenta problemas de hierarquia e naturalidade. Neste trabalho revisitamos os aspectos mais gerais associados a modelos de Technicolor. Em particular, argumentamos que a auto-energia fermiônica deveria apresentar a forma conhecida como Irregular, a qual resolve a maioria dos problemas enfrentados por modelos que seguem esta linha. No último capítulo desta tese elaboramos um modelo, assumindo como solução a forma Irregular para a auto-energia fermiônica, onde as três gerações de férmions adquirem massa via efeitos de quebra dinâmica de simetria. / Abstracts: The Higgs mechanism, based on existence of fundamental scalars bosons suffer from the hierarchy and naturalness problems. In this work we review the main aspects of the Technicolor models. In particular, we aegue that the fermionic self-energy must behave as the Irregular form, that solve most of the Technicolor models problems. In the last Chapter of his thesis we build a model, assuming the Irregular form for the fermionic self-energy, where the three fermionic generations receive mass dynamically. / Doutor

This thesis presents two analyses of data recorded by the ATLAS detector during proton-proton collisions at the LHC. The first is the implementation of a vertex counting algorithm to measure the luminosity recorded by ATLAS during collisions at a centre-of-mass energy of √s = 8 TeV in 2012. This comprises a Monte Carlo closure test for validation of the method and its corrections, the calibration of the method using the van der Meer scans performed in 2012 and the application of the method to physics runs. It also includes tests of the internal and external consistency of the algorithm and the potential to use this algorithm to measure the luminosity of data collected during proton-proton collisions at √s = 13 TeV.The second analysis is the measurement of the inclusive and purely electroweak production of dijets in association with a Z boson, performed using the 3.2 fb−1 of data collected during collisions at a centre-of-mass energy of √s = 13 TeV in 2015. Cross-section measurements are presented for five fiducial regions, each of which has a different sensitivity to the electroweak component of the Zjj production. Data and Monte Carlo predictions are compared and found to be in reasonable agreement for most cases. The electroweak Zjj production cross-section is then extracted in a fiducial region where this contribution is enhanced. This measurement is also in good agreement with the Monte Carlo prediction. These first 13 TeV measurements will set the scene for studies of weak boson fusion, both within the Standard Model and in new phenomena searches, which will become even more important in Run 2 and the future of the LHC due to the electroweak sector not being as constrained yet, compared to the strong sector, and due to the larger enhancements as a result of a higher √s, where electroweak physics can be most easily extracted.

The potential for probing the Standard Model of elementary particle physics by measuring the interactions of W -bosons with Z0-bosons and photons (WW and WWZ triple gauge-boson couplings) using TeV-scale proton-proton collisions is described in the context of the ATLAS detector at the 14 TeV Large Hadron Collider (LHC). The ATLAS detector and LHC are currently under construction at the European Organization for Nuclear Research (CERN), with the rst data expected in 2006. New analysis techniques are presented in this thesis: (1) A new strategy for placing limits on the consistency of measured anomalous triple gauge-boson coupling parameters with the Standard Model is presented. The strategy removes the ambiguities of form factors, by reporting the limits as a function of a cuto operating on the diboson system invariant mass. (2) The `optimal observables' analysis strategy is investigated in the context of hadron colliders, and found to be not competitive, as compared to other strategies. (3) Techniques for measuring the energy dependence of anomalous couplings are presented .. . / Graduate / 0798

An important question at present in particle physics is whether the recently discovered boson with a mass of about 125 GeV is the Standard Model Higgs boson. A Standard Model Higgs boson with a mass of 125 GeV will predominantly decay to b-quark pairs. This work presents the author's contribution to the search with the ATLAS detector for a Standard Model Higgs boson produced in association with a W or Z boson and decaying to b-quark pairs. In order to search for the decay modes ZH → vvb¯b, WH → lvb¯b and ZH → l¯lb¯b, where l is either an electron or muon, events with zero, one or two electrons or muons are considered in 20:3 fb¯1 of 8 TeV LHC data. A Standard Model Higgs boson is not observed decaying to b-quark pairs, although neither is this decay mode ruled out. A Standard Model Higgs boson with a mass of between 110 GeV and 115 GeV is excluded. For mH = 125 GeV the observed (expected) upper limit on the cross- section times the branching ratio is found to be 2.16 (1.07) times the Standard Model prediction. For a Standard Model Higgs boson with a mass of 125 GeV, the best fit signal strength is μ = 1:09 +0:43-0:42 (stat) +0:44-0:37 (syst) = 1:09 +0:61-0:56. The combined results are consistent with a Standard Model Higgs boson with a mass of 125 GeV. The author's own work is presented, including estimation of systematic uncertainties on WH → lvb¯b modelling, and future ATLAS data selection methods for WH → lvb¯b searches. Overviews of underlying theoretical matters and the experimental facilities used are given.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19499号 / 理博第4159号 / 新制||理||1597(附属図書館) / 32535 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川合 光, 教授 畑 浩之, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

A computer code was written to calculate elastic scattering cross sections using the Klein-Gordon equation. The reason for writing this code is because existing codes do not include relativistic kinematics and therefore are only valid for lower energies. This code was used to analyze alpha particle and pion scattering at relativistic energies upon different target nuclei and to find a relativistic potential for a system at a given energy. The target particles in the alpha study were 12C, 40,42,44,48Ca and other alphas. The pions were incident upon 12C and 40Ca. Optical potentials of different forms were used to compare with previous analyses and the experimental data. The potentials found in this study could be useful to understand the physics underlying other processes such as inelastic and particle transfer reactions. The computer code can be used to extend elastic scattering calculations to angles where data does not exist which can then be compared to future experiments. The code could also be used to create a database of potentials for several systems to study the effects of changing charge, mass or energy of the system.

In this thesis we examine the vector boson scattering (VBS) process \(\mathrm p \mathrm p \to \mathrm e^+ \nu_\mathrm e\mu^-\bar\nu_\mu\mathrm j\mathrm j +X\) (short: \(\mathrm W^+\mathrm W^-\) scattering) at NLO accuracy in two experimental setups by performing a Monte Carlo analysis of a \(13\,\mathrm{TeV}\) LHC run. \(\mathrm W^+\mathrm W^-\) scattering shows similarities and differences compared to the scattering of other vector bosons. We present a detailed description of the types of appearing subprocesses and background processes. We give insight into our code which solves the problems we are faced within \(\mathrm W^+\mathrm W^-\) scattering. This is especially the presence of the Higgs-boson resonance in the fiducial phase-space region. Particular attention is dedicated to the permutation of resonances. The integrated signal cross section at LO \(\mathcal O(\alpha^6)\) amounts to \(2.6988(3)\,\mathrm{fb}\) and \(1.5322(2)\,\mathrm{fb}\), respectively, in the two experimental setups. The LO QCD-induced background of \(\mathcal O(\alpha_\mathrm s^2\alpha^4)\) amounts to \(6.9115(9)\,\mathrm{fb}\) and \(1.6923(3)\,\mathrm{fb}\). The EW corrections to the signal are \(-11.4\%\) and \(-6.7\%\), the QCD corrections amount to \(-5.2\%\) and \(-23.0\%\). The EW corrections to the background are \(-8.3\%\) and \(-5.3\%\), the QCD corrections amount to \(-30.3\%\) and \(-77.6\%\). Our results for the QCD corrections and the QCD-induced background include a large uncertainty from varying the renormalisation and factorisation scale, and we discuss improvements for future calculations. We show the differential cross sections with unique features of \(\mathrm W^+\mathrm W^-\) scattering compared to other VBS processes and investigate in particular the subprocess of Higgs-boson production by using a modified version of our setups. / In dieser Arbeit untersuchen wir den Vektorboson-Streuprozess (VBS-Prozess) \(\mathrm p\mathrm p \to \mathrm e^+\nu_\mathrm e\mu^-\bar\nu_\mu\mathrm j\mathrm j + X\) (kurz: \(\mathrm W^+\mathrm W^-\)-Streuung) auf nächstführender Ordnung in zwei Versuchsanordnungen, indem wir eine Monte-Carlo-Analyse des LHC-Betriebs bei \(13\,\mathrm{TeV}\) durchführen. \(\mathrm W^+\mathrm W^-\)-Streuung zeigt Gemeinsamkeiten mit der und Unterschiede zur Streuung anderer Vektorbosonen. Wir stellen eine detaillierte Beschreibung der Arten auftauchender Subprozesse und Hintergrundprozesse vor und geben Einsicht in unseren Code, der die Probleme löst, vor die wir im Rahmen der \(\mathrm W^+\mathrm W^-\)-Streuung gestellt wurden. Dies ist insbesondere die Präsenz der Higgs-Boson-Resonanz im Bezugsphasenraum. Besonderes Augenmerk wird auf die Permutation der Resonanzen gelegt. Wir präsentieren den integrierten Wirkungsquerschnitt. Der integrierte Wirkungsquerschnitt des Signals beträgt \(2{,}6988(3)\,\mathrm{fb}\) beziehungsweise \(1{,}5322(2)\,\mathrm{fb}\) auf führender Ordnung \(\mathcal O(\alpha^6)\) in den beiden experimentellen Setups. Der QCD-Hintergrund auf führender Ordnung \(\mathcal O(\alpha_\mathrm s^2\alpha^4)\) beträgt \(6{,}9115(9)\,\mathrm{fb}\) bzw. \(1{,}6923(3)\,\mathrm{fb}\). Die elektroschwachen Korrekturen zum Signal belaufen sich auf \(-11{,}4\%\) bzw. \(-6{,}7\%\), die QCD-Korrekturen auf \(-5{,}2\%\) bzw. \(-23{,}0\%\). Die elektroschwachen Korrekturen zum Hintergrund sind \(-8{,}3\%\) bzw. \(-5{,}3\%\), die QCD-Korrekturen \(-30{,}3\%\) bzw. \(-77{,}6\%\). Unsere Ergebnisse für die QCD-Korrekturen und den QCD-induzierten Hintergrund enthalten eine große Unsicherheit durch die Variation der Renormierungs- und Faktorisierungsskala und wir diskutieren Verbesserungen für zukünftige Rechnungen. Wir zeigen die differentiellen Wirkungsquerschnitte mit Eigenheiten von \(\mathrm W^+\mathrm W^-\)-Streuung verglichen mit anderen VBS-Prozessen und betrachten insbesondere den Subprozess der Higgs-Boson-Produktion, indem wir eine modifizierte Version unserer Versuchsanordnungen verwenden.

The generation of vector boson mass via the Higgs mechanism in the Standard Model has been confirmed by the 2012 discovery of a candidate Higgs boson in the H&rarr;WW, H&rarr;ZZ, and H&rarr;&gamma;&gamma; decay channels. In contrast, the Yukawa couplings hypothesized to provide the mass of fermions in the Standard Model have yet to be observed. The H&rarr;&tau;&tau; decay channel currently provides the best opportunity for observing these couplings. This thesis describes two separate but related searches for Higgs boson decays in the H→&tau;&tau; decay channel using proton-proton collisions recorded by the ATLAS detector. The first analysis is a general search for all Higgs boson production mechanisms leading to a H&rarr;&tau;&tau; decay using 4.5 fb⁻¹ of 7 TeV and 20.3 fb⁻¹ of 8 TeV proton-proton collision data. A deviation from the background-only hypothesis is observed with a significance of 4.5&sigma; for a hypothetical Higgs boson mass of m_H = 125 GeV — a strong indication of a H&rarr;&tau;&tau; signal. For the same mass point, the best fit value for the signal strength is found to be 1.43 ^&plus;0.43<sub style='position: relative; left: -2.4em;'>−0.37</sub> x the Standard Model expectation. The second analysis is a search for Higgs boson production in association with a vector boson using 20.3 fb⁻¹ of 8 TeV proton-proton collision data. Results in the Z_llH&rarr;_&tau;l&tau;h channel indicate limits of 9.14 x the Standard Model expectation for VH signal production at m_H = 125 GeV. In addition, two studies on enhancement of computing performance in the ATLAS trigger and data analysis pipeline are presented.

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