Die Suche nach dem Higgs-Boson des Standardmodells der Teilchenphysik stellte einen der Hauptgründe für den Bau des Large Hadron Colliders (LHC) dar, dem derzeit größten Teilchenphysik-Experiment der Welt. Die vorliegende Arbeit ist gleichfalls von dieser Suche getrieben. Der direkte Zerfall des Higgs-Bosons in Myonen wird untersucht. Dieser Kanal hat mehrere Vorteile. Zum einen ist der Endzustand, bestehend aus zwei Myonen unterschiedlicher Ladung, leicht nachzuweisen und besitzt eine klare Signatur. Weiterhin ist die Massenauflösung hervorragend, sodass eine gegebenenfalls vorhandene Resonanz gleich in ihrer grundlegenden Eigenschaft - ihrer Masse - bestimmt werden kann. Leider ist der Zerfall des Higgs-Bosons in ein Paar von Myonen sehr selten. Lediglich etwa 2 von 10000 erzeugten Higgs-Bosonen zeigen diesen Endzustand . Außerdem existiert mit dem Standardmodellprozess Z/γ∗ → μμ ein Zerfall mit einer sehr ähnlichen Signatur, jedoch um Größenordnungen höherer Eintrittswahrscheinlichkeit. Auf ein entstandenes Higgs-Boson kommen so etwa 1,5 Millionen Z-Bosonen, welche am LHC bei einer Schwerpunktsenergie von 8 TeV produziert werden. In dieser Arbeit werden zwei eng miteinander verwandte Analysen präsentiert. Zum einen handelt es sich hierbei um die Untersuchung des Datensatzes von Proton-Proton-Kollisionen bei einer Schwerpunktsenergie von 8 TeV, aufgezeichnet vom ATLAS-Detektor im Jahre 2012, auch als alleinstehende Analyse bezeichnet. Zum anderen erfolgt die Präsentation der kombinierten Analyse des kompletten Run-I Datensatzes, welcher aus Aufzeichnungen von Proton-Proton-Kollisionen der Jahre 2011 und 2012 bei Schwerpunktsenergien von 7 TeV bzw. 8 TeV besteht. In beiden Fällen wird die Verteilung der invarianten Myon-Myon-Masse nach einer schmalen Resonanzsignatur auf der kontinuierlichen Untergrundverteilung hin untersucht. Dabei dient die theoretisch erwartete Massenverteilung sowie die Massenauflösung des ATLAS-Detektors als Grundlage, um analytische Parametrisierungen der Signal- und Untergrundverteilungen zu entwickeln. Auf diese Art wird der Einfluss systematischer Unsicherheiten auf Grund von ungenauer Beschreibung der Spektren in Monte-Carlo Simulationen verringert. Verbleibende systematische Unsicherheiten auf die Signalakzeptanz werden auf eine neuartige Weise bestimmt. Zusätzlich wird ein bisher einzigartiger Ansatz verfolgt, um die systematische Unsicherheit resultierend aus der Wahl der Untergrundparametrisierung in der kombinierten Analyse verfolgt. Zum ersten Mal wird dabei die Methode des scheinbaren Signals auf einem simulierten Untergrunddatensatz auf Generator-Niveau angewendet, was eine Bestimmung des Einflusses des Untergrundmodells auf die Anzahl der ermittelten Signalereignisse mit nie dagewesener Präzision ermöglicht. In keiner der durchgeführten Analysen konnte ein signifikanter Überschuss im invarianten Massenspektrum des Myon-Myon-Systems nachgewiesen werden, sodass obere Ausschlussgrenzen auf die Signalstärke μ = σ/σ(SM) in Abhängigkeit von der Higgs-Boson-Masse gesetzt werden. Dabei sind Stärken von μ ≥ 10,13 bzw. μ ≥ 7,05 mit einem Konfidenzniveau von 95% durch die alleinstehende bzw. kombinierte Analyse ausgeschlossen, jeweils für eine Higgs-Boson-Masse von 125,5 GeV. Die erzielten Ergebnisse werden ebenfalls im Hinblick auf die kürzlich erfolgte Entdeckung des neuen Teilchens interpretiert, dessen Eigenschaften mit den Vorhersagen eines Standardmodell-Higgs-Bosons mit einer Masse von etwa 125,5 GeV kompatibel sind. Dabei werden obere Grenzen auf das Verzweigungsverhältnis von BR(H → μμ) ≤ 1,3 × 10^−3 und auf die Yukawa-Kopplung des Myons von λμ ≤ 1,6 × 10^−3 gesetzt, jeweils mit einem Konfidenzniveau von 95%. / The search for the Standard Model Higgs boson was one of the key motivations to build the world’s largest particle physics experiment to date, the Large Hadron Collider (LHC). This thesis is equally driven by this search, and it investigates the direct muonic decay of the Higgs boson. The decay into muons has several advantages: it provides a very clear final state with two muons of opposite charge, which can easily be detected. In addition, the muonic final state has an excellent mass resolution, such that an observed resonance can be pinned down in one of its key properties: its mass. Unfortunately, the decay of a Standard Model Higgs boson into a pair of muons is very rare, only two out of 10000 Higgs bosons are predicted to exhibit this decay. On top of that, the non-resonant Standard Model background arising from the Z/γ∗ → μμ process has a very similar signature, while possessing a much higher cross-section. For one produced Higgs boson, there are approximately 1.5 million Z bosons produced at the LHC for a centre-of-mass energy of 8 TeV. Two related analyses are presented in this thesis: the investigation of 20.7 fb^−1 of the proton-proton collision dataset recorded by the ATLAS detector in 2012, referred to as standalone analysis, and the combined analysis as the search in the full run-I dataset consisting of proton-proton collision data recorded in 2011 and 2012, which corresponds to an integrated luminosity of L = 24.8 fb^−1 . In each case, the dimuon invariant mass spectrum is examined for a narrow resonance on top of the continuous background distribution. The dimuon phenomenology and ATLAS detector performance serve as the foundations to develop analytical models describing the spectra. Using these analytical parametrisations for the signal and background mass distributions, the sensitivity of the analyses to systematic uncertainties due to Monte-Carlo simulation mismodeling are minimised. These residual systematic uncertainties are addressed in a unique way as signal acceptance uncertainties. In addition, a new approach to assess the systematic uncertainty associated with the choice of the background model is designed for the combined analysis. For the first time, the spurious signal technique is performed on generator-level simulated background samples, which allows for a precise determination of the background fit bias. No statistically significant excess in the dimuon invariant mass spectrum is observed in either analysis, and upper limits are set on the signal strength μ = σ/σ(SM) as a function of the Higgs boson mass. Signal strengths of μ ≥ 10.13 and μ ≥ 7.05 are excluded for a Higgs boson mass of 125.5 GeV with a confidence level of 95% by the standalone and combined analysis, respectively. In the light of the discovery of a particle consistent with the predictions for a Standard Model Higgs boson with a mass of m H = 125.5 GeV, the search results are reinterpreted for this special case, setting upper limits on the Higgs boson branching ratio of BR(H →μμ) ≤ 1.3 × 10^−3, and on the muon Yukawa coupling of λμ ≤ 1.6 × 10^−3 , both with a confidence level of 95 %.

The LHC at CERN is now undergoing a set of upgrades to increase the center of mass energy for the colliding particles to be able to explore new physical processes. The focus of this thesis lies on the so called phase II upgrade which will preliminarily be completed in 2023. After the upgrade the LHC will be able to accelerate proton beams to such a velocity thateach proton has a center of mass energy of 14 TeV. One disadvantage of the upgrade is that it will be harder for the atlas detector to isolate unique particle collisions since more and more collisions will occur simultaneously, so called pile-up. For 14 TeV there does not exist a full simulation of the atlas detector. This thesis instead uses data from Monte Carlo simulations for the particle collisions and then uses so called smearing functions to emulate the detector responses. This thesis focuses on how a mono-jet analysis looking for different wimp models of dark matter will be affected by this increase in pile-up rate. The signal models which are in focus are those which try to explain dark matter without adding new theories to the standard model or QFT, such as the effective theory D5 operator and light vector mediator models. The exclusion limits set for the D5 operators mass suppression scale at 14 TeV and 1000 fb-1are 2-3 times better than previous results at 8 TeV and 10 fb-1. For the first time limits have been set on which vector mediator mass models can be excluded at 14 TeV.

The goal of the Q-weak experiment is to make a measurement of the proton's weak charge ($Q^p_W = 1-4\sin^2\theta_W$) to an accuracy of ~4%. This would represent a ~0.3% determination of the weak mixing angle ($\sin^2\theta_W$) at low energy. The measurement may be used for a precision test of the Standard Model (SM) prediction on the running of $\sin^2\theta_W$ with energy scale. The Q-weak experiment operates at Thomas Jefferson National Accelerator Facility (Jefferson Lab). The experiment determines the proton's weak charge by measuring the parity violating asymmetry in elastic electron-proton scattering at low momentum transfer $Q^2 = 0.026 (GeV/c)^2$ and forward angles (~8 degree). The anticipated size of the asymmetry, based on the SM, is about 230 parts per billion (ppb). With the proposed accuracy, the experiment may probe new physics beyond Standard Model at the TeV scale. This thesis focuses on my contributions to the experiment, including track reconstruction for momentum transfer determination of the scattering process, and the focal plane scanner, a detector I designed and built to measure the flux profile of scattered electrons on the focal plane of the Q-weak spectrometer to assist in the extrapolation of low beam current tracking results to high beam current. Preliminary results from the commissioning and the first run period of the Q-weak experiment are reported and discussed.

No description available.

Submitted by CAIQUE MEIRA RONQUI null (cmeiraronqui@gmail.com) on 2018-04-05T02:12:52Z No. of bitstreams: 1 mestrado.pdf: 19390845 bytes, checksum: a1c62d106479845bd9047a91fbad6b1f (MD5) / Approved for entry into archive by Hellen Sayuri Sato null (hellen@ift.unesp.br) on 2018-04-05T16:59:15Z (GMT) No. of bitstreams: 1 ronqui_cm_me_ift.pdf: 19390845 bytes, checksum: a1c62d106479845bd9047a91fbad6b1f (MD5) / Made available in DSpace on 2018-04-05T16:59:15Z (GMT). No. of bitstreams: 1 ronqui_cm_me_ift.pdf: 19390845 bytes, checksum: a1c62d106479845bd9047a91fbad6b1f (MD5) Previous issue date: 2018-02-05 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Elaboramos uma revisão de como o problema da hierarquia aparece na teoria Eletrofraca, pois entendemos que esse assunto ganhou importância e merece atenção especial. Apesar disso, notamos que muitos conceitos necessários para compreender a origem do problema encontram-se espalhados em diferentes livros e artigos, dificultando o acesso à informação. Por isso, apresentamos neste trabalho esses principais conceitos de maneira consolidada. / We develop a review on how the hierarchy problem appears in the Electroweak theory. Nowadays we think that this problem is greater in importance than it was in the past, so it deserves special attention, but we noticed several concepts needed to understand the problem are scattered in different books and papers, which hinders full access to information. Therefore, we intend to present the key subjects in a single document, because we didn't find similar work in previous studies. / 2015/19572-0

Malgré les nombreux succès du Modèle Standard de la physique des particules, plusieurs éléments montrent qu'il ne s'agit que d'une théorie effective à basse énergie. En effet, la masse des neutrinos et la matière noire ne sont pas expliqués dans ce modèle, qui ne prend pas en compte non plus la gravitation dont la version quantique n'a toujours pas été établie. De plus, les divergences quadratiques des corrections à la masse du boson de Higgs dans ce modèle pose un problème de naturalité. Tous ces problèmes indiquent la nécessité de trouver une nouvelle physique, qui doit être décrite par une extension du Modèle Standard. Une des possibilités est d'ajouter une nouvelle symétrie de l'espace-temps, la Supersymétrie, reliant les bosons et le fermions. Dans son extension miminale, la Supersymétrie permet déjà de résoudre le problème de la matière noire en proposant un candidat naturel, le neutralino, et de supprimer les dangereuses corrections quadratiques à la masse du boson de Higgs.Dans cette thèse, les travaux se sont concentrés sur une extension supersymétrique non minimale du Modèle Standard, le NMSSM. Afin de confronter la théorie aux expériences, il est nécessaire de calculer précisément les différentes observables. Ces calculs étant complexes, il est naturel de les automatiser, ce qui a été réalisé à l'aide du code SloopS. Avec ce code, nous avons pu dans un premier temps nous intéresser à la désintégration du boson de Higgs en un photon et un boson Z. Ce mode de désintégration a la particularité d'être généré directement à une boucle, ce qui le rend sensible à la présence de nouvelles particules. Il a commencé à être mesuré lors du Run 1 du LHC et les données vont continuer à s'accumuler avec le Run actuel (Run 2). La possibilité d'une déviation du signal mesuré avec celui prédit par le modèle Standard, requiert donc une analyse théorique préliminaire, que nous avons effectué dans le cadre du NMSSM. Nous nous sommes ensuite intéressé aux corrections radiatives pour des processus plus généraux.Il a d'abord fallu réaliser et implémenter la renormalisation dans SloopS afin de réguler les divergences apparaissant dans ces calculs à une boucle. Puis nous avons pu utiliser le modèle renormalisé pour calculer les corrections radiatives aux masses et largeurs de désintégration des différentes particules supersymétriques et des bosons de Higgs, en comparant les résultats obtenus dans différents schémas de renormalisation. / Although the Standard Model has been very successful so far, it presents several limitations showing that it is only an effective low energy theory. For example, the neutrino masses or dark matter are not predicted in this model. Gravity is also not taken into account and we expect that it plays a quantum role at energies around the Planck mass. Moreover, radiative corrections to the Higgs boson mass suffer from quadratic divergences. All these problems underline the fact that new physics should appear, and this has to be described by an extension of the Standard Model. One well-motivated possibility is to add a new space-time symetry, called Supersymmetry, which link bosons and fermions. In its minimal extension, Supersymmetry can already solve the dark matter paradox with a natural candidate, the neutralino, and provide a cancellation of the dangerous quadratic corrections to the Higgs boson mass.In this thesis, we focussed on the Next-to-Minimal SuperSymmetric extension of the Standard Model, the NMSSM. To compare theoretical predictions with experiments, physical observables must be computed precisely. Since these calculations are long and complex, automatisation is desirable. This was done by developping SloopS, a program to compute one-loop decay width and cross-section at one-loop order in Supersymmetry. With this code, we first analysed the decay of the Higgs boson in a photon and a Z boson. This decay mode is induced at the quantum level and thus is an interesting probe of new physics. Its measurement has been started during Run 1 of the LHC and is continued now in Run 2. The possibility of deviation between the measured signal strength and the one predicted by the Standard Model motivates a careful theoretical analysis in beyond Standard Models which we realised within the NMSSM. Our goal was to compute radiative corrections for any process in this model. To cancel the ultraviolet divergences appearing in higher order computations, we had to carry out and implement the renormalisation of the NMSSM in SloopS. Finally, it was possible to use the renormalised model to compute radiatives corrections to masses and decay widths of Higgs bosons and supersymmetric particles in the NMSSM and to compare the results between different renormalisation schemes.

Les états de charmonium fournissent une source de connaissances pertinente pour déterminer les paramètres fondamentaux du Modèle Standard. Un aspect important de la compréhension et des tests de la QCD est de faire des prédictions précises du spectre des hadrons et de les tester par rapport à des données expérimentales de haute qualité. Notre cadre théorique est Lattice QCD, qui est considéré comme le seul moyen connu de traiter le lagrangien QCD complet de manière non perturbative et bien adaptée au calcul numérique. En utilisant l'action Wilson-Clover avec N_f = 2 saveurs dynamiques, nous étudierons les deux mésons charmonium eta_c et J/\psi. Nous allons également étudier certaines propriétés de leur première excitation radiale eta_c (2S) et \psi(2S). / Charmonium states provide a relevant source of knowledge for determining fundamental parameters of the Standard Model. An important aspect of understanding Quantum ChromoDynamics (QCD) is to make precise predictions of the hadron spectrum and to test them against high-quality experimental data. Our theoretical framework is Lattice QCD, which is considered to be the only known way to treat the full QCD Lagrangian non perturbatively from first principles, in a manner well suited to numerical computation. By using the Wilson-Clover action with N_f = 2 dynamical flavors, we will study the two charmonium mesons eta_c and J/\psi. We will also investigate some properties of their first radial excitations eta_c(2S) and psi(2S).

Les modèles SU(2)xSU(2)xU(1) représentent une étape intermédiaire motivée par l'unification des groupes de jauge du Modèle Standard (MS). Un groupe de jauge étendu, par rapport a celui du MS, implique l'existence de nouveaux bosons de jauge, neutres et charges. Ces bosons dénotés Z' et W' sont recherches activement au Large Hadron Collider (LHC). Sur la base d'une analyse globale récente des contraintes sur ces modèles, provenant des expériences a basse énergie et du LEP, nous effectuons une analyse numérique au Leading Order (LO) des différentes signatures au LHC. Nous montrons que les sections efficaces totales pour les leptons et les paires de quarks de troisième génération, expérimentalement facilement accessibles, fournissent individuellement qu'uneinformation partielles sur le modèle réalise dans la nature. En revanche, les corrélations de ces mêmes sections efficaces pourraient bien conduire a une identification unique. Par la suite, nous étudions la production électrofaible d'une paire de quarks top au Next-to-Leading Order dans les extensions du MS prédisant un boson Z' supplémentaire et en supposant des couplages génériqueset diagonaux dans la base des saveurs. Nous calculons les corrections virtuelles et réelles a l'ordre de O(alS*alW^2) et les implémentons dans le générateur d'événements Monte Carlo POWHEG BOX qui permet de réaliser de manière cohérente la fusion du calcul QCD NLO avec les parton showers. Nousconstatons que les corrections QCD NLO peuvent être très importantes, mais que les K-facteurs restent modestes dans la région de masse invariante centrée autour de la masse de la résonance. / General SU(2)x SU(2)x U(1) models represent a well-motivated intermediate step towards the unication of the Standard Model (SM) gauge groups. Extended gauge group sector, as compared to that of the SM, leads to additional neutral and charged gauge bosons. These so-called Z' and W' bosons are actively searched for at the Large Hadron Collider (LHC). Based on a recent global analysis of low-energy and LEP constraints of these models, we perform numerical scans of their various signals at the LHC at Leading Order accuracy. We show that total cross sections for lepton and third-generation quark pairs, while experimentally easily accessible, provide individually only partial information about the model realized in Nature. In contrast, correlations of these cross sections in the neutral and charged current channels may well lead to a unique identification. Subsequently we study the electroweak top-pair production at Next-to-leading Order (NLO) accuracy in the SM extensions with an additional Z' boson assuming general flavour-diagonal couplings. We calculate the virtual and real corrections at order O(alS*alW^2) and implement them in the POWHEG BOX framework which allows for consistent matching of NLO QCD calculations with parton showers. We find that the NLO corrections can be very important but the K-factors in the invariant mass region around the resonance mass are modest.

This thesis presents the measurement of the differential cross section of Z boson pro-duction in association with jets (Z+jets) in proton-proton collision at the center-of-massenergy of 13 TeV. The data has been recorded with the CMS detector at the LHC duringthe year 2015, corresponding to an integrated luminosity of 2.19 fb −1 .A study of theCMS muon High Level Trigger (HLT) with the data collected in 2016 is also presented.The goal of analysis is to perform a first measurement at 13 TeV of the cross sections ofZ+jets as a function of the jet multiplicity, its dependence on the transverse momentumof the Z boson, the jet kinematic variables (transverse momentum and rapidity), thescalar sum of the jet momenta, and the balance in the transverse momentum betweenthe reconstructed jet recoil and the Z boson. The results are obtained by correctingthe detector effects, and are unfolded to particle level. The measurement are com-pared to four predictions using different approximations: at the leading-order (LO),next-to-leading-order (NLO) and next-to-next-to-leading order (NNLO) accuracy. Thefirst two calculations used M AD G RAPH 5_ A MC@NLO interfaced with PYTHIA 8 for theparton showering and hadronisation, one of which includes matrix elements (MEs) atLO, another includes one-loop corrections (NLO). The third is a fixed-order calculationwith NNLO accuracy for Z+1 jet using the N -jettiness subtraction scheme (N jetti ). Thefourth uses the GENEVA program with an NNLO calculation combined with higher-order resummation.A series of studies on the HLT double muon trigger are also included. Since 2015 theLHC reached higher luminosity, more events are produced inside the CMS detector persecond, which resulted in more challenges for the trigger system. The work presentedincludes the monitoring, validation and the calibration of the muon trigger paths since2016. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Made available in DSpace on 2014-06-11T19:32:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-29Bitstream added on 2014-06-13T21:03:30Z : No. of bitstreams: 1 sanchezvega_bl_dr_ift.pdf: 617259 bytes, checksum: af2a12ec5a0dfc67abebc7c87568c022 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta tese, partículas tais como áxions, Májorons e neutrinos são consideradas em duas extensões eletrofracas do modelo padrão da física de partículas. Especificamente, os modelos considerados estão baseados nas simetrias de gauge SU(3)L ⊗ U(1)X eSU(2)L ⊗U(1)Y⊗U(1)B−L. Primeiramente, no contexto do modelo 3-3-1 com um sector escalar mínimo é realizado um estudo detalhado referente à implementção da simetria de Peccei-Quinn (PQ) para resolver o problema CP forte. Para a versão original do modelo, que possui apenas dois tripletos escalares, é mostrado que a Lagrangiana total é invariante sobre uma simetria PQ. No entanto, o áxion não é produzido porque um sub-grupo permanece sem quebrar. Embora, neste caso, o problema CP forte possa ser resolvido, a solução é amplamente desfavorecida porque três quarks não têm massa em todas as ordens da teoria de perturbação. A adição de um terceiro tripleto escalar resolve o problema dos quarks sem massa, mas o áxion que aparece é visível. Para fazer o modelo realístico teremos que modificá-lo. É mostrado que a adição de um singleto escalar junto com uma simetria de gauge discreta ZN é capaz de levar a cabo esta tarefa e proteger o áxion de efeitos da gravidade quântica. Para ter segurançaa que a simetria de gauge discreta que protege o áxion é livre de anomalias, é usada uma versão discreta do mecanismo de Green-Schwarz. A seguir, é considerado um modelo eletrofraco baseado na simetria de gauge SU(2)L ⊗U(1)Y⊗U(1)B−L, no qual temos neutrinos de mão direita com números quânticos exóticos e diferentes. Devido a esta particular caraterística, é possível termos de massa e de Yukawa para os neutrinos, com campos escalares que podem adquirir valores esperados do vácuo (VEVs) pertencendo a escalas de energia... / In this doctoral thesis axions, Majorons and neutrinos are considered into different electro weak extensions of the standar dmodel of the particle physics. Specifically, the two models considered are based on theSU(3)L ⊗U(1)X andSU(2)L⊗U(1)Y⊗ U(1)B−Lgaugesymmetries. Firstly, in the framework of a 3-3-1 model with a minimal scalar sector a detailed study concerning the implementation of the PQ symmetry in order to solve the strong CP problem is made. For the original version of the model, with only two scalar triplets, it is shown that the entire Lagrangian is invariant under a PQ-like symmetry but no axion is produced since aU(1) subgroup remains unbroken. Although in this case the strong CP problem can still be solved, the solution is largely disfavored since three quark states are left massless to all orders in perturbation theory. The addition of a third scalar triplet removes the massless quark states but the resulting axion is visible. In order to become realistic the model must be extended to account for massive quarks and invisible axion. It is shown that the addition of a scalar singlet together with aZN discrete gauge symmetry can successfully accomplish these tasks and protect the axion field against quantum gravitational effects. To make sure that the protecting discrete gauge symmetry is anomaly free, a discrete version of th eGreen-Schwarz mechanism is used. Secondly, an electroweak model based on the gauge symmetrySU(2)L ⊗U(1)Y⊗ U(1)B−L which has right-handed neutrinos with different quantum numbers is considered. Because of this particular feature it is possible to write Yukawa terms, and neutrino mass terms, with scalar fields that can develop VEVs belonging to different energy scales. A detailed study of the scalar and the Yukawa neutrino sectors is made to show that this model is compatible with... (Complete abstract click electronic access below)