To see the other types of publications on this topic, follow the link: Higgs, Bosons de.
Dissertations / Theses on the topic 'Higgs, Bosons de'
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 'Higgs, Bosons de.'
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
Lietti, S. M. (Sérgio Morais). "Lagrangeanas efetivas e acoplamentos anômalos do bóson de Higgs /." São Paulo, 1998. http://hdl.handle.net/11449/132812.
Full textAbstract:
Orientador: Sérgio Ferraz NovaesBanca: Manuel Drees
Banca: Vicente Pleitez
Banca: Carlos Ourívio Escobar
Banca: Takeshi Kodama
Resumo: 0 Modelo Padrão é, hoje em dia, a melhor formulação teórica para a descrição das interações eletrofracas. 0 acordo entre resultados experimentais e previsões teóricas é expressivo para acoplamentos entre bósons vetoriais e férmions. Porém, possuímos poucas informações sobre o bóson de Higgs, remanescente do mecanismo de quebra de simetria eletrofraca responsável pela geração das massas dos férmions e dos bósons vetoriais. Neste trabalho procuramos explorar alternativas para os acoplamentos do bóson de Higgs aos demais bósons da teoria através do uso de lagrangeanas efetivas. Examinamos as consequências destas novas interações em diversas reações envolvendo a produção e decaimento do bóson de Higgs em colisões elétron-pósitron e hadrônicas. 0 estudo dessas reações nos permite impor vínculos sobre as constantes de acoplamento destas novas interações, os quais são comparados com os limites experimentais das constantes de acoplamento da parametrização convencional dos auto-acoplamentos entre os bósons vetoriais IVWZ e W'gama'.
Abstract: The Standard Model is the best theoretical framework which describes the elec- troweak interactions. The agreement between experimental data and theoretical predictions is spectacular for the fermion-vector boson couplings. However, we have few information concerning the electroweak symmetry breaking sector of the theory. In this Work we explore diíferent possibilities for the couplings among the Higgs boson and the vector bosons of the theory through the use of the effective lagrangian formalism. We examine the consequences of these new interactions in several re- actions involving the Higgs boson production and decay at electron-positron and hadronic collisions. We analyze these reactions in order to impose bounds on the coupling constants of these new interactions. These bounds are compared with the experimental limits on the usual parametrization of the anomalous WWZ and WW'gama'
Doutor
2
Estre, Nicolas Contardo Didier. "Caractérisation des détecteurs silicium, recherche de Vertex et étude du potentiel de découverte d'un boson de Higgs chargé léger dans l'expérience CMS." Villeurbanne : Université Claude Bernard, 2004. http://tel.ccsd.cnrs.fr/docs/00/04/82/96/PDF/tel-00009847.pdf.
Full text
3
Choudhury, Somnath. "Search for Neutral Higgs Bosons decaying to τ Pairs at the CMS experiment." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112206.
Full textAbstract:
La thèse décrit une étude de l'état final en paire de leptons τ dans le mode de désintégration semi-leptonique en muons et hadrons en utilisant des données proton-proton collisions à une énergie de centre de masse de 7 TeV avec le détecteur CMS au CERN Large Hadron Collider. La performance de l'algorithme de reconstruction et d'identification des leptons τ est étudiée en utilisant un échantillon de données de collisions proton-proton à √s = 7 TeV, ce qui correspond à une luminosité intégrée de 36 pb⁻¹. Les leptons τ qui se désintègrent en un seul hadron chargé, avec ou sans hadrons neutres sont reconstruits à l'aide de la technique dite du flot de particules pour la reconstruction des objets en utilisant un nouvel algorithme adapté aux leptons τ et appelé le Hadrons Plus Strips (HPS) qui utilise le trajectographe et le calorimètre électromagnétique de CMS. L'efficacité de l'algorithme de reconstruction est mesurée en utilisant les leptons τ produits lors de la désintégration de bosons Z. Le taux de mauvaise identification de leptons τ se désintégrant de manière hadronique pour les jets produits en association avec un boson W est également déterminé. La première mesure inclusive de production Z→ττ dans les collisions pp au le LHC est présentée dans les états finals muon+jets en utilisant un échantillon de données de 36 pb⁻¹. La section efficace mesurée est en bon accord avec les prédictions QCD à l'ordre doublement suivant l'ordre dominant (NNLO). Après avoir identifié le boson Z dans le mode de désintégration di-τ, une recherche inclusive de bosons de Higgs neutres du modèle supersymétrique standard minimal (MSSM) dans les collisions pp est réalisée à une énergie dans le centre de masse de 7 TeV. Les résultats sont basés sur un échantillon de données correspondant à une luminosité intégrée de 36 pb⁻¹ et de 4,6 fb⁻¹ enregistré par l'expérience CMS dans l'année 2010 et 2011 respectivement. La recherche utilise les désintégrations de bosons de Higgs en paire de leptons τ. Aucun excès n'est observée dans le spectre de masse invariante de paires de leptons τ. Les limites supérieures sur le produit de la section efficace de production de boson de Higgs par le rapport de branchement de la désintégration en paire de leptons τ en fonction de la masse du boson de Higgs pseudoscalaire permettent de donner des limites strictes dans l'espace des paramètres du MSSMThe thesis describes a study of the τ-pair final state in the semi-leptonic decay mode into muon and hadrons using proton-proton collisions data at a center-of-mass energy of 7 TeV using the CMS detector at the CERN Large Hadron Collider. The performance of τ-lepton reconstruction and identification algorithm is studied using a data sample of proton-proton collisions at √s = 7 TeV, corresponding to an integrated luminosity of 36 pb⁻¹. The τ leptons that decay into one charged hadron with or without the association of neutral hadrons is reconstructed using Particle-Flow object reconstruction technique with a novel τ identification algorithm called the Hadron Plus Strips (HPS) algorithm in the CMS tracker and electromagnetic calorimeter. The reconstruction efficiency of the algorithm is measured using τ leptons produced in Z-boson decays. The hadronically decaying τ lepton misidentification rate for jets produced in association with a W boson is also determined. The first measurement of inclusive Z→ττ production in pp collisions at the LHC is presented in muon+hadrons final state using a data sample of 36 pb⁻¹. The measured cross-section is in good agreement with the next-to-next-to-leading order (NNLO) QCD prediction. After establishing the Z boson in di-τ decay mode, an inclusive search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions is performed at a center-of-mass energy of 7 TeV. The results are based on a data sample corresponding to an integrated luminosity of 36 pb⁻¹ and 4.6 fb⁻¹ recorded by the CMS experiment in the year 2010 and 2011 respectively. The search uses decays of the Higgs bosons to τ pairs. No excess is observed in the τ-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross-section times the branching fraction to τ pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent bounds in the MSSM parameter space
4
Braathen, Johannes. "Automating Higgs precision calculations." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS073/document.
Full textAbstract:
L’étude des propriétés du boson de Higgs représente une excellente opportunité pour la recherche de Nouvelle Physique. En particulier, sa masse est mesurée avec une précision impressionnante, de l’ordre de 0.1%, tandis qu’elle est aussi prédite par certains modèles au-delà du Modèle Standard, notamment les modèles supersymétriques. Le but de cette thèse est de faire avancer le calcul des corrections radiatives aux masses des scalaires dans les modèles au-delà du Modèle Standard, ainsi que l’automatisation de ces calculs, afin d’établir ou d’améliorer les limites sur les couplages entre la Nouvelle Physique et le boson de Higgs. Nous calculons d’abord les corrections dominantes à deux boucles, de la forme O(alpha_s alpha_t), aux masses des scalaires neutres dans les modèles supersymétriques à jauginos de Dirac. Ensuite, nous montrons comment surmonter la Catastrophe des Bosons de Goldstone, un cas de divergences infrarouges dues aux bosons de Goldstones de masses nulles qui affecte les calculs de potentiels effectifs, d’équations « tadpoles » et d’énergies propres, en adoptant un schéma de renormalisation « on-shell » pour les masses des bosons de Goldstone. Nous illustrons la mise en œuvre numérique de notre solution dans le programme SARAH, et finalement, nous considérons le comportement aux hautes énergies de modèles non-supersymétriques avec des secteurs scalaires étendusThe Standard Model-like Higgs boson provides an excellent setting for the indirect search of New Physics, through the study of its properties. In particular its mass is now measured with an astonishing precision, of the order of 0.1%, while being predicted in some models of Beyond the Standard Model (BSM) Physics, such as supersymmetric (SUSY) models. The main purpose of this thesis is to push further the calculation of radiative corrections to Higgs boson masses in BSM models, as well as the automation of these calculations, in order to set or improve constraints on New Physics coupling to the Higgs boson. A first chapter is devoted to the computation of the leading two-loop O (alpha_s alpha_t) corrections to neutral scalar masses in SUSY models with Dirac gauginos. Then, we show to address the Goldstone Boson Catastrophe -- a case of infra-red divergences due to massless Goldstone bosons that plague the calculation of effective potentials, tadpole equations, and self-energies -- in the context of general renormalisable field theories, by adopting an on-shell renormalisation scheme for the Goldstone masses. Afterwards, we illustrate the numerical implementation of our solution to the Goldstone Boson Catastrophe in the public tool SARAH. Finally, in a last chapter, we consider the high-scale behaviour of non-supersymmetric models with extended Higgs sectors
5
Ruan, Manqi. "A precise Higgs mass measurement at the ILC and test beam data analyses with CALICE." Paris 11, 2008. http://www.theses.fr/2008PA112172.
Full textAbstract:
En utilisant les outils de Monte Carlo et les données de test en faisceau, la performance d’un détecteur au futur collisionneur linéaire international a été étudiée. La contribution de cette thèse porte sur deux parties; d’une part sur une mesure de précision de la masse du boson Higgs et de la section efficace de la production avec le processus e+e HZ où le boson Z se désintègre en paire et d’autre part sur une analyse des données de test en faisceau de la collaboration CALICE (CAlorimeter for Linear Collider Experiment). Pour un Higgs de 120GeV, nous avons obtenu une précision de 38. 4MeV sur la masse de Higgs et de 5% sur la section efficace en choisissant une énergie dans le centre de masse optimale de 230 GeV et avec une luminosité intégrée de 500 fb-1. Ces résultats sont indépendants d’un modèle de Higgs donné puisque aucune information sur la désintégration du Higgs n’a été utilisée dans l’analyse. Si on suppose que le Higgs est celui du modèle standard ou il se désintègre principalement en particules invisibles, la précision peut être améliorée de façon significative (29MeV pour la masse et 4% pour la section efficace). Pour l’analyse des données de test en faisceau, mon travail concerne deux aspects. Premièrement une vérification sur la qualité des données en temps quasi réel et deuxièmement une mesure précise sur la résolution angulaire d’une gerbe électromagnétique dans le calorimètre prototype utilisé dans le test en faisceau. Le but pour la vérification de la qualité des données est de détecter des problèmes éventuels sur l’ensemble du détecteur y compris l’électronique, le système de haute tension et d’acquisition, et de classer des différentes données pour faciliter les analyses offlines. Pour déterminer la résolution angulaire du calorimètre électromagnétique, nous avons développé un algorithme qui est basée uniquement sur le dépôt d’énergie dans différentes cellules produites par le faisceau d’électrons sans utilisant l’information du détecteur de trace devant le calorimètre. Celle-ci est importante pour pouvoir identifier le composant neutre d’un jet. Nos résultats montrent que la dépendance de la résolution angulaire en énergie du faisceau est similaire à celle de la résolution en énergie et peut être décrite par 80 mrad/√(E/GeV)Utilizing Monte Carlo tools and test-beam data, some basic detector performance properties are studied for the International Linear Collider (ILC). The contributions of this thesis are mainly twofold, first, a study of the Higgs mass and cross section measurements at the ILC (with full simulation to e+e HZ H channel and corresponding backgrounds); and second, an analysis of test-beam data of the CAlorimeter for Linear Collider Experiment (CALICE). For a 120GeV Higgs particle, setting the center-of-mass energy to 230GeV and with an integrated luminosity of 500fb-1, a precision of 38. 4MeV is obtained in a model independent analysis for the Higgs boson mass measurement, while the cross section can be measured to 5%; if we make some further assumptions about the Higgs boson’s decay, for example a Standard Model Higgs boson or a Higgs boson with a dominant invisible decay mode, the measurement results can be improved by 25% (achieving a mass measurement precision of 29MeV and a cross section measurement precision of 4%). For the CALICE test-beam data analysis, our work is mainly focused upon two aspects: data quality checks and the track-free ECAL angular resolution measurement. Data quality checks aim to detect strange signals or unexpected phenomena in the test-beam data so that one knows quickly how the overall data taking quality is. They also serve to classify all the data and give useful information for later offline data analyses. The track-free ECAL angular resolution algorithm is designed to precisely measure the direction of a photon, a very important component in determining the direction of neutral components in jets. We found that the angular resolution can be well fitted as a function of the square root of the beam energy (in a similar way as for the energy resolution) with a precision of approximately 80mrad/√(E/GeV)
6
Efron, Jonathan Zvi. "Search for the Higgs boson in the ZH -> ℓ⁺ℓ⁻bb̄ channel at CDF Run II." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189015468.
Full text
7
Vacavant, Laurent. "Etiquetage des quarks b par un détecteur de vertex à pixels dans l'expérience ATLAS auprès du LHC." Aix-Marseille 2, 1997. https://tel.archives-ouvertes.fr/tel-00011011.
Full textAbstract:
Dans ce travail, les potentialités du détecteur ATLAS pour l'identification des jets issus de quark beau sont étudiées. L'étiquetage topologique, basé sur le paramètre d'impact des traces chargées, est utilisé. Une bonne identification de ces jets sera très précieuse au LHC, en particulier durant les premières années de fonctionnement pour mettre en évidence le cas échéant un boson de Higgs d'une masse comprise entre 80 GeV/c2 et 120 GeV/c2. Pour évaluer les performances dans ce domaine, un algorithme de recherche et reconstruction des traces chargées exploitant la simulation détaillée du détecteur interne d'ATLAS a été réalisé. La recherche est initiée dans les détecteurs à pixels. L'efficacité et la qualité de reconstruction assurent une bonne discrimination entre les jets b et les autres jets. Après simulation complète et reconstruction d'événements H->bbbar, H->gg, H->uubar, H->ssbar et H->ccbar (mH = 100 GeV/c2), les réjections moyennes des jets non-b pour une efficacité d'étiqueter les jets b de 50% sont: Rg = 39+-5 Ru = 60+-9 Rs = 38+-5 Rc = 9+-1 Les résultats de l'analyse des données prises lors de tests en faisceau des premiers prototypes de matrices de détecteurs à pixels en technologie résistante aux radiations justifient les potentialités de ce type de détecteur pour la recherche de traces et la mesure précise de leur paramètre d'impact.
8
Köneke, Karsten [Verfasser], and Karl [Akademischer Betreuer] Jakobs. "Electroweak interactions, the Higgs Boson, and the search for new heavy Bosons." Freiburg : Universität, 2017. http://d-nb.info/1169571735/34.
Full text
9
Parks, Brandon Scott. "Search for the Higgs Boson in the ZH to vvbb channel at CDF run II." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1215108702.
Full text
10
Ayoub, Mohamad Kassem. "Recherche du Boson de Higgs se désintégrant en deux leptons taus dans le canal τlepτhad dans l'expérience ATLAS avec les données à 13 TeV du LHC." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS420/document.
Full textAbstract:
Dans cette thèse, je présente ma contribution à la recherche du boson de Higgs du Modèle Standard dans son canal de désintégration en deux leptons taus dans le sous-canal τlepτhad. J’ai contribué aux différentes étapes de cette analyse. Premièrement, j’ai travaillé sur le développement du framework utilisé pour produire les fichiers d’analyse qui contiennent les informations nécessaires à cette étude. J’ai également participé au développement du framework utilisé pour introduire les prédictions des bruits de fond pour ce canal, tester l’accord entre ces prédictions et les données d’ATLAS, et à la production des fichiers utilisés dans l’étude statistique finale. J’ai également travaillé sur le modèle statistique, qui prend en compte les erreurs statistiques et systématiques, pour en extraire une mesure de la force du signal pour ce canal du couplage du Higgs aux leptons. Ma contribution à l’amélioration de la reconstruction d’un tau hadronique, à l’aide des algorithmes qui identifient les traces de conversion des photons provenant de la désintégration des pions neutres, est également détailléeIn this thesis, I show my contribution to the search for the Standard Model Higgs Boson decaying into two tau leptons in the tlepthad sub-channel. I contributed to the different stages of this analysis. First, I worked on the development of the framework used to produce analysis files that contain the information necessary for this study. I also participated in the development of the framework used to introduce the predictions of the background for that channel, test the agreement between the predictionsand the ATLAS data, and on the production of files used in the final statistical analysis. I also worked on the statistical model, which takes into account the statistical and systematic errors to extract a measure of the signal strength for the Higgs coupling channel to leptons. My contribution to the improvement of reconstruction of a hadronic tau, using algorithms that identify photon conversion traces from the decay of neutral pions, is also detailed
11
Varouchas, Dimitris. "Study of the Higgs boson discovery potential, produced by the vector boson fusion with the ATLAS detector and commissioning of calorimetric transverse missing energy." Paris 11, 2009. http://www.theses.fr/2009PA112217.
Full textAbstract:
Le but de cette thèse est d'évaluer le potentiel de découverte par le détecteur ATLAS au LHC du boson de Higgs du MS. Le mode de production étudié est défini par la fusion de bosons vecteurs (VBF) suivie de la désintégration en une paire de leptons τ (H->τ). C'est l'un des canaux de découverte les plus prometteurs pour un boson de Higgs de basse masse, qui est favorisé par les mesures de précision dans le secteur électro-faible. La topologie caractéristique de VBF, qui est constituée des deux jets vers l'avant du détecteur et des produits de désintégration de boson de Higgs dans la région centrale, fournit une signature unique permettant la suppression du bruit de fond. En outre, puisque le VBF est un processus purement électro-faible, aucune activité de QCD n'est prévue et donc aucun jet central n'est attendu. Ceci permet l'application de la coupure de «central jet veto» pour encore réduire le bruit de fond. Une analyse basée sur des coupures a été utilisée, se concentrant sur l'optimisation de la coupure de «central jet veto». L'objectif principal était d'étudier le potentiel de découverte du boson de Higgs avec ATLAS,sous une luminosité intégrée de 30 fb-1 dans la gamme de masse mH=(115,140) GeV pour une énergie au centre de la masse of 14 TeV. Après l'application des coupures, un excès au-dessus de 5ƒb-1 de signal significance a été est trouvé pour la gamme de masse mH=(115,125). Pour le canal H->ττ, la résolution de l'énergie transverse manquante (ETmiss ) est importante puisqu'elle affecte directement la résolution sur la masse du boson de Higgs. Cela a été la motivation initiale pour réaliser et présenter dans cette thèse une étude de «commissioning» calorimétrique basée sur les quantités ETmiss , plus particulièrement sur la contribution du bruit de l' électronique, mesurée dans des événements cosmiques. Un comportement gaussien de bruit dans tous les calorimètres de l'argon liquide a été trouvé, tandis qu'un comportement non-gaussien dans une partie du calorimètre a tuile scintillante du a un bruit cohérent, a été observé. Pour ce dernier, un nouveau modèle de bruit a été examiné utilisant une paramétrisation de double gaussienne ayant pour résultat une description plus réalisteThe subject of this thesis is the evaluation of the discovery potential of the ATLAS detector at the LHC for the SM Higgs boson in vector boson fusion (VBF) production and a subsequent decay into a τ-lepton pair (H->ττ). This is one of the most promising discovery channels in the low mass range, which is the mass range favored from precision measurements of the electroweak interaction. The characteristic VBF topology, which consists of two jets in the forward regions of the detector and the Higgs boson decay products in the central region, provides a unique signature allowing the suppression of background. In addition, since VBF is a purely electroweak process, no QCD activity is expected and thus no central jets are expected. This allows the central jet veto cut application to further reject background processes. A cut-oriented analysis was used, focusing on the central jet veto cut optimization. The main objective was to investigate the Higgs boson ATLAS discovery potential with an integrated luminosity of 30 fb-1 in the mass range mH=(115,140) GeV, for an LHC energy at the center of mass of 14 TeV. After the application of all cuts, an excess above 5σ of signal signifcance was found for the mass range mH=(115,125). In H->ττ decay channel, transverse missing energy (ETmiss) resolution is of high importance since it affects directly the resolution of the Higgs boson mass. This was the initial motivation for performing and presenting in this thesis a calorimetric commissioning study based on ETmiss quantities, focused on the electronics noise ETmiss contribution, measured with cosmics data of the period fall 2008. A Gaussian behavior of noise in all liquid argon calorimeters was found, whereas a region of non-Gaussian tails in scintillating tile calorimeter due to a coherent noise, was high-lighted. For the latter, a new noise model was tested using a double Gaussian parameterization resulting in a more realistic description
12
Wouda, Glenn. "Phenomenology of Higgs Bosons Beyond the Standard Model." Doctoral thesis, Uppsala universitet, Högenergifysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-240617.
Full textAbstract:
After a long history of searches, a Higgs boson H was discovered by the ATLAS and the CMS experiments at the Large Hadron Collider (LHC) in 2012. Its properties fit well the ones predicted by the Standard Model (SM) of particle physics. However, the SM can not explain other established properties of Nature, such as the existence of Dark Matter. For this reason, models beyond the SM should be considered. Such models often predict the existence of several Higgs bosons and this thesis explores some of those models. In particular, the possibility to discover a charged Higgs boson, which would be a clear sign of physics beyond the SM, is studied. A commonly studied extension of the SM is the framework of two-Higgs-doublet models (2HDMs), where there are five Higgs bosons. By confronting the parameter spaces of some 2HDMs with publically available data from the LHC, the prospects for finding the 2HDM Higgs bosons is presented through the calculation of production cross sections and decay branching ratios in various channels. A new kind of 2HDM, called the Stealth Doublet Model is presented and the properties of the Higgs bosons are studied. In this model, it is shown that in particular the properties of the charged Higgs boson H± have new features not exhibited in earlier studied models. Within the parameter space compatible with the LHC results, the production cross section for H± can be sizeable enough to be experimentally observed. Finally, the discovery prospects at the LHC, for a H± in the pp → tH± process, with the decays H± → HW± and H → bb, is studied in various models beyond the Standard Model. It is shown that for the supersymmetric models, this channel is beyond the discovery reach of the LHC. In some of the other studied models, in particular the Aligned 2HDM, the situation is improved and the channel is feasible.
13
Koukoutsakis, Athanasios. "Higgs bosons and QCD jets at two loops." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3652/.
Full textAbstract:
In this thesis we present techniques for the calculation of two-loop integrals contributing to the virtual corrections to physical processes with three on-shell and one-off-shell external particles. First, we describe a set of basic tools that simplifyy the manipulation of complicated two-loop integrals. A technique for deriving helicity amplitudes with use of a set of projectors is demonstrated. Then we present an algorithm, introduced by Laporta, that helps reduce all possible two-loop integrals to a basic set of 'master integrals'. Subsequently, these master integrals are analytically evaluated by deriving and solving differential equations on the external scales of the process. Two-loop matrix elements and helicity amplitudes are calculated for the physical processes γ* → qqg and H → ggg respectively. Conventional Dimensional Regularization is used in the evaluation of Feynman diagrams. For both processes, the infrared singular behaviour is shown to agree with the one predicted by Catani.
14
Rodríguez, Vázquez Matiás. "Search for supplementary Higgs Bosons at the LHC." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS317/document.
Full textAbstract:
Malgré un succès expérimental incontestable, le Modèle standard (MS) de la physique des particules laisse de nombreuses questions fondamentales sans réponse, comme le problème de hiérarchie et l’origine de la matière noire, motivant l’étude de la « nouvelle physique ». Le Modèle Standard Supersymétrique Non-Minimal (MSSNM) est une extension très intéressante du MS répondant à ces deux problèmes. Il comprend une riche phénoménologie, en principe accessible au Grand Collisionneur de Hadrons (LHC). En particulier, son secteur de Higgs est étendu par rapport au MS, générant six scalaires. Le but de cette thèse est d’étudier le potentiel de découverte de ces bosons de Higgs supplémentaires au LHC. Après une introduction du MSSNM et de ses motivations, nous étudions d’abord les perspectives de découverte d’un scalaire, plus léger que la résonance à 125 GeV mise en évidence au CERN, en passant en revue ses possibles modes de production et de détection dans les phases à venir du LHC, et ses possibles impacts sur les couplages du boson de Higgs du MS. Ensuite, les perspectives de recherche via les cascades de Higgs, impliquant des bosons de Higgs supplémentaires légers et lourds, est présentée. Des études détaillées au moyen de méthodes Monte-Carlo ont été réalisées, et de nouvelles analyses dédiées sont présentées. Ces derniers résultats ne sont pas restreints au MSSNM, et peuvent être interprétés dans une large classe de modèlesDespite its incontestable experimental success, the Standard Model of particle physics leaves unanswered many fundamental questions like the hierarchy problem and the origin of dark matter, motivating the study of physics beyond its scope. The NMSSM is a well-motivated extension of the SM addressing these two issues. It features a rich phenomenology accessible, in principle, at the LHC. In particular, the Higgs sector of the NMSSM is extended with respect to the SM giving rise to six scalars. It is the aim of this thesis to study the discovery potential of these extra Higgs bosons at the LHC. After introducing the NMSSM and its motivation, we first study the discovery prospects for a scalar lighter than the 125 GeV resonance found at CERN, reviewing its possible production and detection at the upcoming runs of the LHC and its possible impact on couplings of the Standard Model Higgs boson. Next, prospects for searches via Higgs cascades involving extra light and heavy Higgs bosons are presented. Detailed studies by means of Monte Carlo methods are performed, and new dedicated analysis are proposed. These last results are not confined to the NMSSM and can be interpreted in a wide class of models
15
Akeroyd, Andrew Gerard. "Signals of non-minimal Higgs sectors at future colliders." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5288/.
Full textAbstract:
This thesis concerns the study of extended Higgs sectors at future colliders. Such studies are well motivated since enlarged Higgs models are a necessity in many extensions of the Standard Model (SM), although these structures may be considered purely in the context of the SM, to be called the 'non-minimal SM'. The continuous theme of the thesis is the task of distinguishing between the (many) theoretically sound non-minimal Higgs sectors at forthcoming colliders. If a Higgs boson is found it is imperative to know from which model it originates. In particular, the possible differences between the Higgs sectors of the Minimal Supersymmetric Standard Model (MSSM) and the non-minimal SM are highlighted. Considered first are the detection prospects of light charged Higgs scalars (H(^±)) at e(^+)e(^-) colliders. The discovery of a H(^±) would provide unambiguous evidence for a non- minimal Higgs sector. We show that in certain (but not all)non-minimal models a light H(^±) may exist i.e. be within the mass range accessible at LEP2 (M(_H)(_ ±) ≤ Mw). In particular the MSSM requires M(_H±) ≥ Mw, and thus detection of a at LEP2 is strong evidence against the MSSM. We discuss ways of distinguishing between the models which may contain a light H(^±) by exploiting differences in the decay channels. Attention is then given to the neutral Higgs bosons of the non-minimal SM. It is possible that these particles may possess a greatly different phenomenology to that of the mammal SM and MSSM, and we explore the feasibility of observing these differences at LEP2 and the LHC It is found that distinct, sometimes spectacular signatures are possible. The thesis next considers a more exotic Higgs representation, namely that of Higgs triplets, and compares its phenomenology at LEP2 with that of the non-minimal models covered thus far The phenomenon of Higgs bosons decoupling from the fermions(fermiophobia) arises naturally in the above triplet model, and this concept is studied in more depth in the final chapter. It is emphasized that such particles are not possible in the MSSM.
16
Lietti, Sérgio Morais [UNESP]. "Lagrangeanas efetivas e acoplamentos anômalos do bóson de Higgs." Universidade Estadual Paulista (UNESP), 1998. http://hdl.handle.net/11449/132812.
Full textAbstract:
Made available in DSpace on 2016-01-13T13:28:05Z (GMT). No. of bitstreams: 0
Previous issue date: 1998. Added 1 bitstream(s) on 2016-01-13T13:33:37Z : No. of bitstreams: 1
000087537.pdf: 1761894 bytes, checksum: 30e7908292072ce33a74fe28d9e4d5a6 (MD5)
17
Tonasse, M. D. [UNESP]. "O setor escalar em modelos com simetria de Gauge 'SU(3) IND.L' x 'U(1) IND.N' das interações eletrofracas." Universidade Estadual Paulista (UNESP), 1993. http://hdl.handle.net/11449/132862.
Full textAbstract:
Made available in DSpace on 2016-01-13T13:28:16Z (GMT). No. of bitstreams: 0
Previous issue date: 1993. Added 1 bitstream(s) on 2016-01-13T13:31:40Z : No. of bitstreams: 1
000027041.pdf: 1309141 bytes, checksum: 0e0a71d58ec7ac8f649404883fabd269 (MD5)
18
Tonasse, M. D. "O setor escalar em modelos com simetria de Gauge 'SU(3) IND.L' x 'U(1) IND.N' das interações eletrofracas /." São Paulo, 1993. http://hdl.handle.net/11449/132862.
Full text
19
Prado, Leônidas Augusto Fernandes do. "Teorias efetivas e violação de sabor leptônico em decaimentos do Higgs /." São Paulo, 2015. http://hdl.handle.net/11449/154697.
Full textAbstract:
Orientador: Ricardo D'Elia MatheusBanca: Oscar José Pinto Eboli
Banca: Rogério Rosenfeld
Resumo: Consideramos o decaimento do Higgs violando sabor leptônico h→ 'tau' 'mü' no contexto de teorias efetivas. O CMS divulgou recentemente um excesso de eventos de 2,5 'sigma' neste canal. O operador responsável por este processo, no entanto, está em muitos casos correlacionado com operadores de dipolo, que já têm fortes restrições experimentais. Exploramos então em que casos é possível de se obter um operador de violação de sabor grande o suficiente para ser visto em decaimentos do Higgs no LHC, porém ainda respeitando os limites encontrados em decaimentos radiativos de léptons. Apresentamos também dois modelos, um do tipo Higgs Composto e outro do tipo Higgs Portal, mostrando como o processo h→ 'tau' 'mü' surge em cada um deles. Caso o sinal do CMS seja confirmado, o segundo modelo será favorecido, enquanto é improvável que o primeiro consiga o explicar
Abstract: We consider the Higgs Lepton Flavor Violating decay h→ 'tau' 'mü' in the framework of effective theories, on which CMS reported a 2.5 σ excess of events. The operator that is responsible for this process, however, is in many models correlated to dipole operators that are already under stringent experimental constraints. We then explore in which cases it is possible to obtain a flavor violating operator that is big enough to be seen in Higgs decays at the LHC, while still respecting the leptonic radiative decay bounds. We also present two models, a simplified Composite Higgs model and a Higgs Portal model, showing how the process h→ 'tau' 'mü' is generated in each of them. We find that if the CMS signal is confirmed, the second model is favored, while it is unlikely that the first model will be able to explain it
Mestre
20
Prado, Leônidas Augusto Fernandes do [UNESP]. "Teorias efetivas e violação de sabor leptônico em decaimentos do Higgs." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/154697.
Full textAbstract:
Made available in DSpace on 2018-07-27T18:26:07Z (GMT). No. of bitstreams: 0
Previous issue date: 2015-06-17. Added 1 bitstream(s) on 2018-07-27T18:30:16Z : No. of bitstreams: 1
000866736.pdf: 1452961 bytes, checksum: 319c3fa13bbe5e0dc4754274971c2c02 (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Consideramos o decaimento do Higgs violando sabor leptônico h→ 'tau' 'mü' no contexto de teorias efetivas. O CMS divulgou recentemente um excesso de eventos de 2,5 'sigma' neste canal. O operador responsável por este processo, no entanto, está em muitos casos correlacionado com operadores de dipolo, que já têm fortes restrições experimentais. Exploramos então em que casos é possível de se obter um operador de violação de sabor grande o suficiente para ser visto em decaimentos do Higgs no LHC, porém ainda respeitando os limites encontrados em decaimentos radiativos de léptons. Apresentamos também dois modelos, um do tipo Higgs Composto e outro do tipo Higgs Portal, mostrando como o processo h→ 'tau' 'mü' surge em cada um deles. Caso o sinal do CMS seja confirmado, o segundo modelo será favorecido, enquanto é improvável que o primeiro consiga o explicar
We consider the Higgs Lepton Flavor Violating decay h→ 'tau' 'mü' in the framework of effective theories, on which CMS reported a 2.5 σ excess of events. The operator that is responsible for this process, however, is in many models correlated to dipole operators that are already under stringent experimental constraints. We then explore in which cases it is possible to obtain a flavor violating operator that is big enough to be seen in Higgs decays at the LHC, while still respecting the leptonic radiative decay bounds. We also present two models, a simplified Composite Higgs model and a Higgs Portal model, showing how the process h→ 'tau' 'mü' is generated in each of them. We find that if the CMS signal is confirmed, the second model is favored, while it is unlikely that the first model will be able to explain it
21
Dalchenko, Mykhailo. "Measurements of the Higgs boson mass and width in the four-lepton final state and electron reconstruction in the CMS experiment at the LHC." Palaiseau, Ecole polytechnique, 2014. https://tel.archives-ouvertes.fr/tel-01115325/document.
Full textAbstract:
Ce document de thèse traite de la mesure de la masse et de la largeur du nouveau boson découvert récemment au Large Hadron Collider (LHC), candidat pour être le boson de Higgs du modèle standard. L’analyse utlise les collisions protons-protons enregistrées par le détec- teur Compact Muon Solenoid (CMS) au LHC, correspondant à des luminosités integrées de 5. 1 fb−1 à 7 TeV d’énergie dans le centre de masse et de 19. 7 fb−1 à 8 TeV d’énergie dans le centre de masse. Les événements selectionnant le boson de Higgs via sa désintégration en ZZ, ou les bosons Z se désintègrent en paires d’électrons ou de muons, ont été exploités pour la mesure des propriétés du boson de Higgs. Une mesure précise de la masse a été effectuée et vaut 125. 6 ± 0. 4(stat) ± 0. 2 (syst) GeV. Des contraintes sur la largeur du boson de Higgs ont été établies en utilisant sa production hors-masse et sa désintégration en une paire de bosons Z, ou un des Z se désintègre en paire d’électrons ou de muons, et l’autre en une paire d’électrons, de muons ou de neutrinos. Le résultat obtenu est une limite supérieure sur la largeur du boson de Higgs à 22 MeV à 95% de niveau de confiance, ce qui correspond à 5. 4 fois la valeur attendue pour le modèle standard à la masse mesurée. Une attention particulière a été apportée à l’estimation de l’impulsion des électrons. La combinaison de l’estimation de l’impulsion par le trajectomètre et la mesure de l’énergie déposée dans le calorimètre électromagnétique, permettant une amélioration significative de la mesure de l’impulsion des électrons de bassse impulsion transverse, a été ré-optimisée et a joué un rôle essentiel dans la découverte du boson Higgs dans le canal en quatre leptons. L’échelle d’énergie ainsi que la résolution en énergie des électrons a été mesurée avec une grande précision en utilisant les bosons de Z se désintégrant en électronsThis thesis document reports measurements of the mass and width of the new boson re- cently discovered at the Large Hadron Collider (LHC), candidating to be the Standard Model Higgs boson. The analysis uses proton-proton collision data recorded by the Compact Muon Solenoid (CMS) detector at the LHC, corresponding to integrated luminosities of 5. 1 fb−1 at 7 TeV center of mass energy and 19. 7 fb−1 at 8 TeV center of mass energy. Set of events selecting Higgs boson via the H → Z Z decay channel, where both Z bosons decay to electron or muon lepton pairs, is used for the Higgs boson properties measurements. A precise measurement of its mass has been performed and gives 125. 6 ± 0. 4(stat) ± 0. 2 (syst) GeV. Constraints on the Higgs boson width were established using its off-shell production and decay to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The obtained result is an upper limit on the Higgs boson width of 22 MeV at a 95% confidence level, which is 5. 4 times the expected value in the standard model at the measured mass. Throughout the thesis, a particular attention has been put on the elec- tron momentum estimation. The combination of the momentum estimate with the tracker and the energy measurement with the electromagnetic calorimeter, allowing a significant improvement of the low transverse impulsion electrons measurement of the momentum, has been revisited and played an essential role in the Higgs boson discovery in the 4 leptons decay channel. The electron energy scale and resolution have been measured with very high precision using the Z boson decaying in electrons
22
Machado, Ana Carolina Bruno. "Resolvendo o problema dos sabores /." São Paulo : [s.n.], 2011. http://hdl.handle.net/11449/102497.
Full textAbstract:
Orientador: Vicente PleitezBanca: Alex Gomes Dias
Banca: William Antonio Ponce Gutierrez
Banca: Alberto Gago Medina
Banca: Hiroshi Nunokawa
Resumo: Neste trabalho, propomos duas extensões multi-Higgs do modelo padrão com simetrias discretas abelianas e não abelianas e com o setor escalar que possui pelo menos um dubleto de Higgs para cada férmion do MP. Mostramos que do ponto de vista fenomenológico os modelos concordão com os dados experimentais e as massas e as matrizes de mistura CKM e PMNS são corretamente obtidas, para o primeiro modelo que descreve o setor dos quarks e dos léptons e para o segundo modelo, que descreve somente o setor dos léptons a matriz de mistura PMNS e as massas são devidamente obtidas
Abstract: In this work we propose two multi-Higgs extension of the Standard Model with Abelian and non Abelian discrete symmetries and a scalar sector which has at least one Higgs doublet for each fermion of the Standard Model. From the phenomenological point of view the models are safe and the masses and the mixing matrices CKM and PMNS are properly obtained for the first model that describes the sector of quarks and leptons. The second model describes only the leptonic sector, but the mixing matrix and masses are also obtained in compliance with the experimental data
Doutor
23
Mastrolorenzo, Luca. "Search for the Higgs boson decaying into tau lepton pairs with the Matrix Element Method and tau trigger optimization in the CMS experiment at the LHC." Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01257354/document.
Full textAbstract:
J’ai effectué ma thèse en physique des particules au laboratoire Leprince-Ringuet à l’École Polytechnique. J’ai participé à l’analyse des collisions proton-proton à 8 TeV produites par le Large Hadron Collider (LHC) et collectées par le détecteur CMS. La découverte du boson de Higgs a été un événement majeur pour la physique des hautes énergies car la masse des bosons vecteurs provient de leur interaction avec le champ de Higgs. Le couplage du boson de Higgs avec les leptons n’ayant pas encore été découvert, mon travail de thèse s’est articulé autour du canal de désintégration en pair de tau, car c’est le seul qui permet de mettre ce couplage en évidence. En effet, le boson de Higgs se désintègre beaucoup plus souvent en taus qu’en muons ou électrons. Cette analyse est difficile au niveau du déclenchement. En effet, l’important bruit de fond impose d’appliquer des seuils en énergie élevés. Un critère de déclenchement utilisant l’énergie transverse manquante pour abaisser le seuil sur les leptons a été introduit à la fin de la prise de données. Cette approche permet de récupérer 41% d’événements en plus. J’ai effectué une caractérisation exhaustive de ce déclenchement, et en particulier étudié les erreurs systématiques associées au niveau de l’analyse. Ce déclenchement a permis d’améliorer de 2% la limite d’exclusion dans le canal Higgs en tau-tau semi-leptonique. Au Run 2, l’énergie des collisions a été portée à 13 TeV et la luminosité va augmenter. Pour garantir un déclenchement efficace pour la physique, le premier niveau du système de déclenchement (L1) a été remplacé en se basant sur la technologie microTCA. Ce nouveau système permet un accès à des informations plus détaillées en provenance du détecteur. J’ai développé, pour ce nouveau système, un algorithme de sélection des taus basé sur un algorithme d’agrégation dynamique exploitant au maximum la granularité du calorimètre. J’ai mesuré ses performances en terme d’efficacité et de taux de déclenchement, et pour la première fois auprès d’un collisionneur hadronique, CMS disposera en 2016 d’un déclenchement efficace sur les taus au L1 avec un taux raisonnable. J’ai présenté ce travail sous forme de poster à la conférence ICHEP 2014. Dans la dernière partie de ma thèse, je me concentre sur la recherche du boson de Higgs se désintégrant en une paire de taus, en me concentrant sur le canal semi-leptonique et en introduisant pour la première fois la méthode des éléments de matrice (MEM) qui permet d’améliorer la sensibilité par rapport aux méthodes traditionnelles. Aucune analyse utilisant la MEM avec des taus n’a jamais été publiée. L’innovation dans ce travail consiste notamment dans le traitement de la désintégration des taus. La réponse du détecteur est quant-à-elle modélisée par des fonctions de transfert. Puis, j’ai du tenir compte des limitations numériques intervenants dans l’évaluation des intégrales multidimensionnelles à la base de cette méthode. Enfin, j’ai mesuré le gain en sensibilité apporté par la méthode sur les données à 8 TeV. Les performances dans le cadre de la recherche du boson de Higgs se désintégrant en une paire de tau de cette méthode pionnière sont très prometteuses, avec un rapport S/B amélioré d’un facteur 3, et constituent une référence pour l’analyse des futures données du Run 2 du LHCI performed my thesis work in Particle Physics at the Laboratoire Leprince-Ringuet of the Ecole Polytechnique. I have participated to the analysis of the 8 TeV proton-proton collisions produced by the Large Hadron Collider (LHC) and collected by the CMS experiment. The discovery of the Higgs boson has been a major breakthrough in particle physics as the mass of the vector bosons are explained through their interactions with the Higgs field. I worked on the newly discovered Higgs boson analysis. As its direct coupling to fermions remained to be exhibited, I focused on the search for the Higgs boson decaying in tau lepton pairs. The Higgs decay into a tau pair is the only channel allowing the couplings between the Higgs boson and the leptons to be measured. This is due to the large event rate expected in the Standard Model compared to the other leptonic decay modes. The Higgs boson decaying to tau lepton analysis is particularly challenging at the trigger level because the large background imposes high thresholds. I worked on a trigger that ran at the end of the data-taking using the missing transverse energy to lower the threshold on the single lepton. This approach allows the recovery of 41% of the signal events. Events with missing transverse momentum were selected in order to control the trigger rate. My personal contribution consisted in a thorough characterization of this trigger, including the measure of the associated uncertainty. The results of this approach led to an amelioration of 2% in the exclusion limits computed in the Higgs to taus semileptonic channel. For the Run 2, the center-of-mass energy of the LHC collisions has been increased to 13 TeV and the instantaneous luminosity will reach 2E34/cm2/s. To guarantee a successful and ambitious physics program under this intense environment, the CMS Trigger and Data acquisition system has been consolidated. In particular the Level 1 (L1, hardware based first level of the CMS trigger system) benefited from the recent microTCA technology allowing the calorimeter granularity to be better exploited with more advanced algorithms. Thanks to the enhanced granularity provided by the new system, an innovative dynamic clustering technique has been developed to obtain an optimized tau selection algorithm. I took the responsibility of developing a complete new tau trigger algorithm at L1 and measuring its performance. This original approach resulted in the first hardware tau lepton trigger efficient at a hadron collider with a sustainable rate. I had the opportunity to present a poster showing my work at the ICHEP-2014 conference, in Valencia and the proceedings were published in Nuclear Physics B afterwards. During my last year of PhD I focused on the Higgs decays into di-taus analysis, initiating the very first matrix element (ME) approach in this channel, starting with the most sensitive final state: the semileptonic decay mode. The aim is to increase the sensitivity of the analysis to the SM Higgs boson, with respect to the traditional methods. No ME-based analysis using tau leptons has ever been published. The novelty of my work is the treatment of the tau decay. In addition, I have derived a parameterization of the detector response through transfer functions. Finally, the numerical aspects related of multidimensional integrals computations have been tackled. I have fully characterized the method using simulated samples before applying it to the 8 TeV data. The performance in the context of the CMS Higgs into di-taus of this pioneering method are very promising, with a S/B ratio improved by a factor 3, and constitute a baseline for the analysis of the upcoming Run 2 data of the LHC
24
Teyssier, Daniel Martin Jean-Paul. "Recherche du boson de Higgs standard et non-minimal à LEP2 dans l'expérience L3." Villeurbanne : Université Claude Bernard (Lyon 1), 2002. http://tel.ccsd.cnrs.fr/docs/00/04/50/30/PDF/tel-00001929.pdf.
Full text
25
Lindahl, Viveca. "Detection Prospects of Doubly Charged Higgs Bosons from the Higgs Triplet Model at the LHC." Thesis, Uppsala universitet, Högenergifysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-155961.
Full textAbstract:
In this thesis I explore the possibilities of detecting doubly charged Higgs bosons from the Higgs Triplet Model (HTM) at the Large Hadron Collider (LHC) at CERN. Higgs bosons are included into the Standard Model (SM) of particle physics in order to explain the origin of mass of the elementary particles. Even though the SM is considered to be a reliable starting point for any particle theory, no Higgs particles have to this day been found. There are therefore high expectations for the record-breaking energies of the LHC to lead to a Higgs discovery. The HTM produces seven different Higgs bosons, and among these we find the doubly charged ones. Because of their exotic charge, I focus on studying these Higgs particles in particular. To this purpose, I implement the full HTM theory as an alternative model option in standard particle physics Monte-Carlo software and then simulate LHC proton-proton collisions at a center of mass energy of 14 TeV. The investigated signal is defined as two like-signed leptons, four hard jets and missing energy in the final state. The main production mechanisms are pair-production and associated production with a singly charged Higgs. Since I choose to study a region of parameter space where the triplet vacuum expectation value is relatively large, the doubly charged Higgs decays into W's and the singly charged Higgs into WZ or tb. The results of the simulations show that the LHC could probe Higgs masses up to at least 300 GeV with an integrated luminosity of about 300 fb.1.
26
Xie, Si Ph D. Massachusetts Institute of Technology. "Search for the Standard Model Higgs boson decaying to two W bosons at CMS." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77499.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 255-264).
In this thesis, we search for the production of the Standard Model Higgs boson at the Large Hadron Collider, through its decay mode to two W bosons, which each in turn decay into a charged lepton and a neutrino. The Higgs boson is the only elementary particle predicted by the Standard Model of particle physics which has not yet been experimentally observed. The question of its existence has been the subject of a wide body of experimental and theoretical work for the past half-century. Using 4.9 fb-1 of integrated luminosity, this search is expected, on average, to exclude the Standard Model predicted Higgs boson production cross section for masses between 126 GeV/c 2 and 260 GeV/c 2 under the background-only hypothesis. We observe no statistically significant excesses in the data, and we exclude the Standard Model Higgs boson production for masses between 129 GeV/c 2 and 260 GeV/c 2 . This result represents a significant reduction of the mass region in which the Standard Model Higgs boson is allowed to exist.
by Si Xie.
Ph.D.
27
Courbon, Benoit. "Reconstruction des photons et recherche d’un second boson de Higgs dans le canal di-photon au sein de l’expérience CMS au LHC." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1187/document.
Full textAbstract:
Une particule compatible avec le boson de Higgs du modèle standard de la physique des particules a été découverte au grand collisionneur de hadrons (LHC) en juillet 2012 par les expériences Atlas et CMS. A ce jour, l'ensemble des mesures des couplages de ce boson de Higgs sont compatibles avec ceux prédits par le modèle standard. Toutefois le modèle standard possède des limitations et d'autres théories, telles la supersymétrie, ont été bâties afin de pallier à ces manques. Certaines de ces théories prédisent en particulier un secteur scalaire enrichi avec la présence de bosons de Higgs additionnels.D'un point de vue expérimental, le canal de désintégration du boson de Higgs en deux photons offre une signature claire et permet d'explorer le secteur de Higgs avec une grande précision. Les travaux présentés dans cette thèse ont été effectués dans le cadre de l'expérience CMS au LHC.La première partie est dédiée à l'étude de la reconstruction expérimentale des photons. Tout d'abord, une méthode de correction en énergie des photons est exposée. Puis des prospectives concernant l'évolution de la qualité de leur reconstruction avec le vieillissement du détecteur sont présentées.La deuxième partie fait l'objet de la recherche d'un second boson de Higgs de basse masse(en dessous de 110 GeV) dans le canal di-photon. Les résultats complets obtenus avec le jeu de données collecté en 2012, ayant fait l'objet d'une publication officielle, sont tout d'abord présentés. Les premiers résultats obtenus avec le jeu de données collecté en 2015 sont enfin introduitsA particle compatible with the Standard Model Higgs boson has been discovered at the Large Hadron Collider (LHC) in July 2012 by Atlas and CMS experiments. All the couplings measurements are so far compatible with those predicted by the Standard Model. However, this model is not able to address several fundamental physics issues and theories beyond the Standard Model, such as supersymmetry, have been proposed to address these questions. Some of them predict an extended Higgs sector with additional scalar or pseudoscalars at low mass.On the experimental point of view, the diphoton decay channel provides a clear signature and allows us to explore the Higgs sector with high precision.The studies presented in this thesis have been performed using the data collected by CMS at the LHC.The first part of the document is dedicated to photon reconstruction studies. First, a photon energy correction method is presented. Then, photon reconstruction performance is assessed in the context of the Phase I and Phase II detector upgrades, in high luminosity conditions.The second part of the document is dedicated to the search for an additional light Higgs boson (with a mass below 110 GeV) in the diphoton channel. First, the official results corresponding to the full 2012 dataset are exposed. Finally, results corresponding to 2015 data are presented
28
Buszello, Claus Peter. "Bestimmung der Kopplungsstruktur des Higgs-Bosons mit dem Atlas-Detektor." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=970692889.
Full text
29
Raspereza, Alexei. "Search for neutral Higgs bosons in e+e--collisions." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=972652744.
Full text
30
Eriksson, David. "Phenomenology of Charged Higgs Bosons and B-meson Decays." Doctoral thesis, Uppsala universitet, Kärn- och partikelfysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9564.
Full textAbstract:
For more than 30 years the Standard Model has been the theoretical foundation for particle physics. The theory has been verified successfully by experimental tests. Its biggest shortcoming is the non-discovery of the Higgs boson,responsible for giving the other particles masses. Despite its success there are hints that the Standard Model is not the complete theory and many extensions of it, such as supersymmetry, have been proposed. Extended theories often predict the existence of a charged Higgs boson and its detection will be a clear sign of physics beyond the Standard Model. The main focus in this thesis is on various phenomenological aspects of the charged Higgs boson. For favorable mass and couplings direct detection is shown to be possible at the Large Hadron Collider in production with an associated W boson. It is also shown how a light charged Higgs can have measurable effects on spin correlations in decays of pair-produced top quarks. The charged Higgs boson can also be seen indirectly, in for example B-meson decays, which can be used to put constraints on its mass and fermion couplings. Exclusion limits in two supersymmetric models are given together with a comparison with the discovery potentials for the LHC experiments. A tool for calculating properties, such as masses and decays, of both charged and neutral Higgs bosons in the Two-Higgs-Doublet Model is also presented. B-meson decays can also be used to test aspects of the strong interaction. Part of this thesis deals with improving and applying phenomenological models to B-meson decays. Although these models are not derived from first principles, their success shows that they capture important features of non-perturbative strong interactions.
31
Coniavitis, Elias. "Charged Higgs Bosons at the ATLAS Experiment and Beyond." Doctoral thesis, Uppsala universitet, Högenergifysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-111576.
Full textAbstract:
In the ATLAS experiment at the Large Hadron Collider (LHC) at CERN, direct searches for the elusive Higgs boson will be conducted, as well as for physics beyond the Standard Model. The charged Higgs boson (H±) is interesting both as a part of the Higgs sector, and as a clear sign of new physics. This thesis focuses on H± searches, with H± production in top-antitop pair events, and in particular the bW± bH±, H±→τhadν, W±→qq channel. Its potential was investigated as part of a larger study of the expected performance of the entire ATLAS experiment. Full simulation of the ATLAS detector and trigger was used, and all dominant systematics considered. It was shown to be the most promising H± discovery channel for mH±<mt. As hadronic τ decays are important for H± searches, their correct identification is critical. Possibilities of improving tau-jet identification in pile-up and top-antitop pair events were investigated. Redundant or even performance-reducing variables in the default likelihood identification were identified, as were new variables showing discriminatory power. This allows for increased rejection of QCD jets in these environments, and higher robustness of the method. Before any physics studies, a commissioned and well-understood detector is required. The Lorentz angle of the ATLAS Semi-Conductor Tracker (SCT) barrel was measured using 2008 cosmic-ray data. It is an important observable for the performance of several detector aspects. Potential sources of systematics were investigated and evaluated. The Lorentz angle in the SCT barrel was measured as θL = 3.93 ± 0.03(stat) ± 0.10(syst) degrees, agreeing with the model prediction. The Compact Linear Collider (CLIC) is a proposed successor to the LHC. The potential for charged and heavy neutral Higgs bosons at CLIC was investigated, in terms of both discovery and precision measurement of parameters like tanβ or the Higgs masses, up to and beyond 1 TeV, which would be challenging at the LHC
32
Bates, Ross Taylor. "Two photon decay widths of non-standard Higgs bosons." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26774.
Full textAbstract:
This thesis examines the two photon decay widths of non-standard Higgs bosons. These widths are calculated for Two-Higgs-Doublet models in general, and for the minimal broken supersymmetry model in particular. For Two-Higgs-Doublet models a large enhancement of these widths relative to the standard model is possible. This in turn leads to larger production rates for the spin-0 bosons in ep and e⁺e⁻ colliders. However, we find that for the minimal broken supersymmetry case, a severe upper bound on this possible enhancement is imposed by the supersymmetry features. We find that while the Higgs bosons of the Two-Higgs-Doublet model could possibly be produced at readily observable rates with the HERA collider, this will not be the case in the minimal supersymmetry model. Hence detection of these Higgs bosons could provide an experimental test of supersymmetry, which would rule out the minimal model.Science, Faculty of
Physics and Astronomy, Department of
Graduate
33
Osman, Nicolas Ahmed. "A Search for Neutral Supersymmetric Higgs Bosons at DO." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525230.
Full text
34
Tuchming, Boris. "Recherche de bosons de higgs supersymetriques dans l'experience aleph." Paris 11, 2000. http://www.theses.fr/2000PA112107.
Full textAbstract:
Une recherche des bosons de higgs neutres du modele standard et de son extension supersymetrique minimale (mssm) est effectuee dans les canaux a quatre jets, e +e hz q$$qb$$b et e +e ha b$$bb$$b. A cette fin, les donnees enregistrees dans le detecteur aleph aupres du lep en 1998 et 1999 pour des energies dans le centre de masse de 189 gev a 202 gev sont analysees. Les deux selections, reposent avant tout sur l'etiquetage des quarks beaux qui est realise a l'aide d'un reseau de neurones associant les informations venant de la reconstruction precise des trajectoires des particules chargees, de l'impulsion transverse des leptons, et de la cinematique des jets. Des variables topologiques et cinematiques signant la production de quatre jets sont ensuite combinees au contenu en b des evenements pour definir les selections b$$bb$$b et q$$qb$$b. En appliquant ces selections aux donnees enregistrees dans aleph, aucun exces d'evenements revelant la presence d'un signal n'est observe. Cela conduit a contraindre la masse du boson de higgs standard et l'espace des parametres possibles du mssm. Les limites suivantes a 95% de niveau de confiance sont donc etablies : m h > 107. 4 gev/c 2 dans le modele standard et m h > 91. 6 gev/c 2 dans le mssm. D'autre part, pour les valeurs de references des parametres du mssm, l'intervalle 0. 8 < tan < 1. 9 est exclu, ainsi que le scenario point fixe infra-rouge a petit tan.
35
Raspereza, Alexei. "Search for neutral higgs bosons in e+e- collisions." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2004. http://dx.doi.org/10.18452/15117.
Full textAbstract:
Diese Arbeit beschreibt die Suche nach dem Higgs Boson, welches in vielen theoretischen Modellen der Teilchenphysik vorhergesagt wird. Das Higgs Boson ist die Konsequenz der spontanen Symmetriebrechung, welche den Teilchen Masse verleiht. Zur Suche werden e+e- Annihilationen bei Schwerpunktenergien bis 209 GeV analysiert, welche vom Experiment L3 am Speicherring LEP in den Jahren 1998 bis 2000 registriert wurden. Die Suche erfolgte in allen relevanten Endzustaenden, wobei der Endzustand mit vier hadronischen Jets im Detail behandelt wird. Die Daten werden mit den Erwartungen eines Signals in verschiedenen Modellen bei Beruecksichtigung der bekannten Untergrundprozesse verglichen oder es wird modellunabhaengig nach der Erzeugung skalarer Teilchen gesucht. Die Produktion von Higgs Bosonen konnte nicht nachgewiesen werde. Die Daten wurden daher benutzt, um neue Grenzen fuer Parameter der Modelle oder der Kopplungen zu setzen. Als erstes wird die Suche nach dem Higgs Boson im Standard Modell der elektroschwachen Wechselwirkung beschrieben. Die Produktion des Higgs Bosons wird bei LEP Energien ueber die Higgs-Strahlung und der Zerfall des Higgs Bosons in ein Paar von b-Quarks vorhergesagt. Die Analysen beruhen daher wesentlich auf der Erkennung von B-Hadronen. Der HZ->qqqq Endzustand wird im Detail untersucht, und die Ergebnisse werden mit den anderen Kanaelen : HZ->qqvv, HZ->qql+l- und HZ->tau+tau- qq kombiniert. Die untere Massengrenze fuer das Higgs Boson wird zu mH > 112.0 GeV auf 95% Vertrauensniveau, bestimmt. Ausserdem werden Grenzen auf die HZZ Kopplung abgeleitet. Im minimalen supersymmetrischen Modell (MSSM) werden fuenf Higgs Bosonen vorhergesagt. Zur Higgs-Strahlung kommt die Paarproduktion von Higgs Bosonen, e+e- -> hA , hinzu. Die Ergebnisse der Suche im Standard Modell werden durch die Suche in den Endzustaenden bb tau+tau- (tau+tau- bb), bbbb und hZ->AAqq ergaenzt. Im Rahmen von drei Standard-Szenarien, benannt als "mh-max", "no mixing" und "large-mu" werden untere Grenzen auf die Higgs Boson Massen von mh > 84.5 GeV und mA > 86.3 GeV fuer tan(beta) > 0.7 abgeleitet. Weiterhin werden im "mh-max" Szenario 0.55 < tan(beta) < 2.2, im "no mixing" Szenario 0.4 < tan(beta) < 4.9, und im "large-mu" Szenario 0.7 < tan(beta) < 6.2 ausgeschlossen. Eine modellunabhaengige Suche nach dem Prozess e+e- -> hZ wird fuer den vier-Jet Endzustand durchgefuehrt. In Kombination mit den Ergebnissen von den anderen Kanaelen werden Grenzen fuer die hZZ Kopplung bestimmt. Wird die hZZ Kopplung auf den Wert im Standard Modell gesetzt und der Zerfall des Higgs Bosons zu 100% in Hadronen angenommen, ergibt sich als Grenze der Higgs Boson Masse, mh > 97 GeV. Modellunabhaengige obere Grenzen fuer die hAZ Kopplung werden aus der Suche nach der Paarerzeugung von Higgs Bosonen in den Kanaelen hA->qqqq und hA->qq tau+tau- in Abhaengigkeit von den Higgs Boson Massen abgeleitet. Die Resultate aus der Kombination aller LEP Experimente werden fuer die oben genannten Analysen vorgestellt. Die Perspektiven der Higgs Boson Suche an den TEVATRON und LHC Speicherringen werden diskutiert und die Higgs Boson Physik an kuenftigen e+e- Linearbeschleunigern behandelt. Ein Linearbeschleuniger wie TESLA waere ideal fuer Untersuchungen eines leichten Higgs Bosons. Fuer ein Higgs Boson mit einer Masse zwischen 120 und 180 GeV kann mH mit einer Praezision von 40 bis 70 MeV bestimmt werden. Im gleichen Massenbereich ist die Messung des Wirkungsquerschnitts, weitgehend modellunabhaengig, mit einem relativen Fehler von 2.6 bis 3.8% moeglich. In vier-Fermion und sechs-Fermion Endzustaenden werden topologische Wirkungsquerschnitte, definiert als Produkt des totalen Wirkungsquerschnitts fuer e+e- -> HZ mit dem Verzweigungsverhaeltnis eines Zerfallskanals, untersucht. Fuer den Messfehler werden 1.1% fuer HZ->bbqq und 13% fuer HZ->W+W-l+l- bei mH = 120 GeV abgeschaetzt. Die Gesamtheit dieser und weiterer Messungen erlaubt eine genaue Bestimmung des Higgs Boson Profils und gibt Aufschluss ueber die Struktur des Higgs Sektors in der Natur.This thesis is devoted to the search for neutral Higgs bosons predicted by various theoretical models. The Higgs boson arises as a result of spontaneous breaking of SU(2) symmetry leading to the generation of masses of fermions and weak bosons. The search is done in all experimentally related channels using the data collected at center-of-mass energies up to 209 GeV in the years 1998-2000 with the L3 detector at the Large Electron Positron collider, LEP. Here the study of the final states characterised by four jets is described in detail. For other final states the analyses are briefly reviewed and the results are reported. The data are compared with the expectation from the Standard Model background processes and with various signal hypotheses. A model independent search for neutral Higgs bosons is also performed. No evidence for the production of Higgs bosons is found. New mass limits are determined superseding previous mass limits established by L3 and other experiments. First I describe the analysis searching for the Standard Model Higgs Boson. Its production at LEP is expected mainly via the Higgs-strahlung process. In the mass range accessible at LEP the Standard Model Higgs Boson is predicted to decay dominantly into a pair of b and anti-b quarks, hence the dedicated analyses are optimised for the H->bb decay mode. The four-jet signal topology is investigated and then combined with the other search channels leading to a lower mass limit of mH > 112.0 GeV at 95% C.L.. The results of the search are also interpreted in terms of limits on the HZZ coupling. In the Minimal Supersymmetric Standard Model (MSSM) the Higgs sector is extended to five physical states. The Higgs-strahlung process is complemented by the mechanism of the Higgs boson pair production e+e- -> hA. Therefore, for the interpretation of the results in the framework of the MSSM the Standard Model analyses are combined with the hA -> bb tau+tau-, hA -> bbbb and hZ->AAqq channels. Three benchmark MSSM scenarios denoted "mh-max", "no mixing" and "large-mu" are considered. Using L3 data the lower bounds on the Higgs boson masses mh > 84.5 GeV mA > 86.3 GeV are derived at 95% C.L. for tan(beta) > 0.7. For the "mh-max", "no mixing" and "large-mu" scenarios, ranges 0.55 < tan(beta) < 2.2, 0.4 < tan(beta) < 4.9 and 0.7 < tan(beta) < 6.2, respectively, are ruled out. A model independent search for the Higgs-strahlung process with subsequent decay of h into hadrons is carried out in the four-jet channel. The results of the analysis are then combined with the other channels. A limit on the hZZ coupling as a function of the Higgs boson mass is derived. The results of L3 combined search establish a 95% C.L. lower mass limit, mh > 97 GeV, for a hadronically decaying Higgs boson assuming the cross section of the Higgs-strahlung process to be equal to the value predicted by the Standard Model and the branching fraction of the Higgs boson into hadrons equal to 100%. Analyses are developed to search exclusively for the hA -> bbbb, hA -> qqqq, hA -> bb tau+tau- and hA -> qq tau+tau- final states. Results of these analyses are translated into a 95% C.L. upper limit on the hAZ coupling as a function of Higgs boson masses. Searches for neutral Higgs bosons carried out by the L3 collaboration are combined with searches performed in other LEP experiments. The results of this combination are reported. The perspectives of Higgs boson searches at TEVATRON and LHC are briefly reviewed. The prospects of Higgs physics at a future linear e+e- collider are discussed. The potential of the TESLA detector foreseen at the TESLA linear collider for the determination of Higgs boson properties is studied. The Higgs boson masses 120, 150 and 180 GeV are considered. It is shown that a precision of 40 - 70 MeV in the measurement of the Higgs boson mass can be achieved. A model independent method to measure the e+e- -> HZ cross section is proposed. The method is based on the study of the inclusive HZ -> X e+e- and X mu+mu- channels. The relative error in the determination of the cross section varies between 2.6% and 3.8% for Higgs boson mass ranging from 120 GeV to 180 GeV. For the four-fermion and six-fermion final states arising from the Higgs-strahlung process the accuracy of the measurement of a topological cross section, defined as the product of the Higgs-strahlung cross section and the branching fraction of the specific final state, is investigated. The relative uncertainty of this measurement varies from 1.1% and 13%, depending on final state and Higgs boson mass. These and other measurements will allow to determine the profile of the Higgs boson and give insight into the structure of the Higgs sector in nature.
36
Espitalier-Noël, Grégory. "Phénoménologie des extensions supersymétriques non-minimales du Modèle Standard de la physique des particules." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20221/document.
Full textAbstract:
La découverte d'une particule similaire au boson de Higgs, dernière pièce manquante du Modèle Standard (MS) de la physique des particules élémentaires, est en voie d'être confirmée par les expériences CMS et ATLAS du Large Hadron Collider du CERN. Cependant, il n'est pour le moment pas encore établit que les caractéristiques de la particule observée correspondent aux prédictions du MS. Cela, associé à d'autres observations (Matière Noire,...), motive l'analyse des extensions supersymétriques du MS comme le NMSSM. Nous étudions dans cette thèse la solution au problème de la hiérarchie des échelles d'énergie dans le NMSSM, lié aux divergences quadratiques de la masse du boson de Higgs, ainsi que la phénoménologie du NMSSM avec une brisure de la supersymétrie par interactions de jauge en tenant compte des dernières données du LHC. Enfin, nous détaillons les développements des codes de NMSSMTools effectués au cours de cette thèse~: l'introduction de Chaînes de Markov, le calcul du Fine Tuning, le calcul des cascades de désintégrations des partenaires supersymétriques en particules du MS et l'implémentation du NMSSM généralThe discovery of a particle similar to the Higgs boson predicted by the Standard Model (SM) of particle physics has been confirmed by the experiments CMS and ATLAS of the Large Hadron Collider at the CERN. However, it is not yet clear that the properties of this particle are those predicted by the SM. This, in addition with several other observations (Dark Matter,...), is a motivation for analysing supersymmetric extensions of the SM, as the NMSSM. We study in this thesis the solution of the Hierarchy problem in the NMSSM, linked with the quadratic divergences in the Higgs sector, and also the phenomenology of the NMSSM with gauge mediation supersymmetry breaking in the light of the latest data from the LHC. Finally, we present the developments made in the codes of the package NMSSMTools, featuring Monte Carlo Markov Chain methods, Fine Tuning calculus, the calculus of supersymmetric particle's cascade decays and the implementation of the general NMSSM
37
Meineck, Christian. "Coupling measurement of the Higgs boson and search for heavy Higgs like bosons via the decay channel \hwwlnln with the ATLAS experiment." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-178250.
Full textAbstract:
Diese Arbeit pr\"asentiert zwei Analysen des Zerfallskanals \hwwlnln mit den Daten des ATLAS experiments am LHC. Die analysierten Daten wurden im Jahr 2011 bzw. 2012 bei einer Schwerpunktsenergie von $\sqrt{s} = 7 \TeV$ bzw. $8 \TeV$ aufgezeichnet und es wurde eine integrierte Luminosit\"at von $25\,\textrm{fb}^{-1}$ erreicht. Die beiden Analysen unterscheiden sich im analysierten Phasenraum, der von der Massen $m_{\rm H}$ des Higgs boson Signals
abh\"angt. Die Analyse f\"ur Massen $m_{\rm H} < 200 \GeV$ wurde \"uber die letzten Jahre optimiert, um in der Lage zu sein, eine Pr\"azisions Messung der Kopplungen einer Resonanz bei $m_{\rm H} \approx 125 \GeV$ durchzuf\"uhren. Dabei wird ein Likelihood Fit der transversalen Masse $\mT = \sqrt{ (E_{T}^{\ell \ell} + P_{T}^{\nu \nu})^2 - | \vec{P_{T}^{\ell \ell}} + \vec{P_{T}^{\nu \nu}|^2} }$ angewendet. Mit einer statistischen Signifikanz von $6.1 \sigma$ konnte ein \hwwlnln Signal bei einer Masse $m_{\rm H} = 125.36 \pm 0.41 \GeV$ beobachtet werden. Die Messung der Signalst\"arke, dem Verh\"altniss von experimentell bestimmtem Produktionswirkungsquerschnitt mal Verzweigungsverh\"altnis zur theoretischen Prognose, ergab folgenden Wert:
\begin{align*}
\mu &= 1.08\,^{+0.16}_{+0.15} \textrm{(stat.)} \,^{+0.16}_{-0.14} \textrm{(syst.)},
\end{align*}
was im Einklang mit der Standard-Modell-Vorhersage steht. Die Skalierung der Kopplungen des Higgs bosons an
Fermionen und Bosonen wurden bestimmt zu:
\begin{align*}
\kappa_{F} &= 0.92\,^{+0.30}_{-0.23}\\
\kappa_{V} &= 1.04\,^{+0.10}_{-0.11}.
\end{align*}
Zur Suche nach schweren, Higgs boson artigen Teilchen wurde die Analyse des \\ \hwwlnln Zerfallskanals f\"ur Massen $m_{\rm H} > 200 \GeV$ optimiert. Auch im hohen Massenbereich wird ein Likelihood Fit an der Verteilung der transversalen Masse \mT durchgef\"uhrt.
Es wurden obere Grenzen auf Produktionswirkungsquerschnitt mal Verzweigungsverh\"altnis f\"ur drei Szenarien bestimmt: Standard-Model-Higgs-Boson im Massenbereich $200 \leq m_{\rm H} \leq 1 \TeV$,
Higgs boson artige Resonanz mit einer Zerfallsbreite von $1 \GeV$ im Massenbereich $200 \leq m_{\rm H} \leq 2 \TeV$ und das elektroschwache Singlet Szenario im Massenbereich $200 \leq m_{\rm H} \leq 1 \TeV$, bei dem die Zerfallsbreite zus\"atzlich zur Masse variiert wird.
Es konnte in keinem getesteten Szenario ein statistisch signifikanter Daten\"uberschuss beobachtet werden und dar\"uberhinaus konnte ein Standard Modell artiges Higgs Boson bis zu einer Masse von $m_{\rm H} = 661 \GeV$ ausgeschlossen werden.Two analyses of the decay channel \hwwlnln using the data of the ATLAS experiment at LHC are presented here. The data was recorded in the years 2011 and 2012 with a center of mass energy of $\sqrt{s} = 7 \TeV$ and $8 \TeV$, respectively, with a total integrated luminosity of $25\,\textrm{fb}^{-1}$ reached. The two presented analyses differ in the analyzed phase space, which depends on the mass $m_{\rm H}$ of the analyzed Higgs boson signal. The analysis for masses $m_{\rm H} < 200 \GeV$ is optimized to perform a high precision measurement of the couplings of the resonance at $m_{\rm H} \approx 125 \GeV$. A binned likelihood fit of the transverse mass distribution $\mT = \sqrt{ (E_{T}^{\ell \ell} + P_{T}^{\nu \nu})^2 - | \vec{P_{T}^{\ell \ell}} + \vec{P_{T}^{\nu \nu}|^2} }$ is used to obtain the results. A signal originating from a Standard Model Higgs boson with a mass $m_{\rm H} = 125.36 \pm 0.41 \GeV$ has been observed at a statistical significance of $6.1 \sigma$. The signal strength, defined as the ratio of the measured production cross section times branching ratio over the theoretical prediction, is: \begin{align*} \mu &= 1.08\,^{+0.16}_{+0.15} \textrm{(stat.)} \,^{+0.16}_{-0.14} \textrm{(syst.)}, \end{align*} which is in good agreement with the data and with the Standard Model prediction. The scaling factors of the couplings of the Higgs boson to fermions and bosons have been measured as: \begin{align*} \kappa_{F} &= 0.92\,^{+0.30}_{-0.23}\\ \kappa_{V} &= 1.04\,^{+0.10}_{-0.11}, \end{align*} which is also in good agreement with the Standard Model prediction. In order to search for heavier Higgs like particles, the analysis of \hwwlnln decays is also optimized for masses $m_{\rm H} \geq 200 \GeV$. As in the analysis optimized for $m_{\rm H} < 200 \GeV$, a binned likelihood fit of the transverse mass \mT is used. Upper limits on the product of production cross section and branching ratio have been obtained for three scenarios: Standard Model Higgs boson in the mass range $200 \leq m_{\rm H} \leq 1 \TeV$, a Higgs like particle with a decay width of $1 \GeV$ in the mass range $200 \leq m_{\rm H} \leq 2 \TeV$ and the electroweak singlet scenario in the mass range $200 \leq m_{\rm H} \leq 1 \TeV$ with the decay width being an additional free parameter. No statistically significant excess of the observed data over the expectation is observed, and a heavy Standard Model Higgs boson is excluded up to a mass of $m_{\rm H} = 661 \GeV$.
38
Rauch, Daniel [Verfasser]. "Aspects of Rare Production and Decay Processes of the Higgs Boson : Aspekte von seltenen Produktions- und Zerfallsprozessen des Higgs-Bosons / Daniel Rauch." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1223095924/34.
Full text
39
Hallberg, Jesper. "Study of charged Higgs bosons using multi-jet final states with the ATLAS experiment at the LHC." Thesis, Uppsala universitet, Högenergifysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227536.
Full textAbstract:
The ATLAS experiment at the LHC is searching for evidence of charged Higgs bosons, without yet finding it. This report investigates the possibility of reconstructing charged Higgs bosons using multi-jet final states (pp -> [b]tH+ -> [b]bbbql\nu) with focus on fully hadronic H^+ -> hW decays using a simulation of 500k events with m_{H+} = 250 GeV. After optimizing TMVA (Toolkit for Multivariate Analysis) input variables for BDT (Boosted Decision Trees), the mass of H+ was recreated with an efficiency of up to 26,7% (correct combinations).
40
Relefors, Johan. "Studies of charged Higgs bosons at the Compact Linear Collider." Thesis, Uppsala universitet, Högenergifysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-155420.
Full textAbstract:
The Compact Linear Collider is an electron-positron collider being developed by CERN and collaborating universities. With a center of mass energy of 3 TeV it will be used to further explore TeV scale physics after the Large Hadron Collider. This thesis is part of the simulation studies which are currently being performed for the CLIC conceptual design report (CDR). In the framework of the Minimal Supersymmetric Standard Model (MSSM) the reconstruction of charged Higgs boson pairs at CLIC is studied using a full detector simulation. Methods for measuring the mass, decay width and branching ratios of the charged Higgs boson are presented. The mass and decay width measurements focus on fully hadronically decaying charged Higgs boson pairs and it is possible to achieve a precision of a few GeV. The branching ratio can be measured with an accuracy ofabout 2%. Studies of top-tagging in fully hadronic charged Higgs boson decays are also presented. A top-tagging efficiency per event of about 60% is achieved. Top-tagging is also tested on the process H0A0 to bbbb and it is shown that top-tagging can be used to discriminate between fully hadronically decaying charged Higgs bosons and H0A0 to bbbb with a rejection power of about 6 to 1. The study is limited by the fact that there are no simulations with hadronic background from beam-beam effects and no simulations of the Standard Model backgrounds are available at the time of writing.
41
Dunne, Patrick James. "Searches for invisibly decaying Higgs bosons with the CMS detector." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/41978.
Full textAbstract:
Searches for invisibly decaying Higgs bosons using the Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) and their interpretations are described. These searches are motivated both by a desire to characterise the newly observed Higgs boson, and by the cosmological observation of very weakly interacting matter in the universe, which is called dark matter. In order to provide context for these searches, introductions to the Standard Model (SM) of particle physics and several extensions to the SM which incorporate dark matter are given. The searches described in this thesis use data recorded in proton-proton collisions in 2012 and focus on the most sensitive mode, Vector Boson Fusion (VBF) production. The first search uses 19.5 fb 1 of data promptly reconstructed in 2012 and results in an observed (expected) limit on the invisible branching fraction of the 125 GeV Higgs boson, B (H -> inv), of 0.65 (0.49) at the 95% confidence level (CL) [1]. The second search uses 19.2 fb 1 of data collected using triggers with looser thresholds and reconstructed later, in 2013. This search resulted in an observed (expected) limit on B (H -> inv) of 0.57 (0.40) at the 95% CL [2]. Combinations of these searches with searches in other production channels are also described, the most sensitive of which results in an observed (expected) limit on B (H -> inv) of 0.36 (0.30) at 95% CL [3]. Projections of the sensitivity of these analyses in Run 2 and interpretations of their results as limits on various models of dark matter are also given [4].
42
Dumitriu, Ana Elena. "Study of the Higgs production in association with tt quarks." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0295/document.
Full textAbstract:
Le travail scientifique présenté dans cette thèse s’appuie sur des collisions proton proton, à 13 TeV dans le centre de masse, produite par le grand collisionneur de Hadron (LHC) et enregistrées entre 2015 et 2017 par le détecteur ATLAS. Après une brève introduction sur le programme de physique du LHC, le premier chapitre donne un aperçu complet du contexte et des motivations théorique. Ensuite une description complète du détecteur ATLAS et plus généralement de l’ensemble expérimental est donnée. Le troisième chapitre traite d’une des mesures des performances du calorimètre électromagnétique ATLAS, à savoir l’étude des efficacités identification électronique à l’aide de W se désintégrant en électrons et neutrinos.Dans les chapitres suivants, le coeur de cette thèse, la recherche et l’étude de la production associée de boson de Higgs avec une paire de quark top, appelée production ttH, est traitée dans le schéma du modèle Standard et au-delà. L’observation de la production ttH avec le détecteur ATLAS a été récemment annoncée en 2018 et représente une étape importante pour le domaine de la physique des hautes énergies. Afin d’élargir le spectre de cette analyse tth au-delà du SM, cet état final du canal 4L a aussi été étudié dans le cadre de la recherche de bosons de Higgs doublement chargés se désintégrant en W$^{\pm}$W$^{\pm}$, H$^{\pm \pm} \rightarrow $ W$^{\pm}$W$^{\pm}$. En conclusions, les perspectives sur les futurs résultats scientifiques dans le modèle Standard (SM) ainsi que au-delà de SM (BSM) qui pourraient être atteint en utilisant les statistiques complètes des Run1 et Run2 combinés sont donnésThe scientific work presented in this thesis is based on proton proton collision produced, at 13 TeV in the center of mass, created by the Large Hadron Collider (LHC) and recorded between 2015 and 2017 by the ATLAS detector.After a short introduction on the physics program at LHC, the first chapter gives a comprehensive overview of the theoretical context and motivation. Then a complete description of the ATLAS detector and more generally the experimental setup is given with a highlight on the different physics objects used in this research.The third chapter is dealing with a measure of the performances of the ATLAS electromagnetic calorimeter, namely the study of the electron identification efficiencies using W decaying into electrons and neutrinos events.In the following chapters, the core of this thesis work, the search and study of the associated Higgs boson production with top quark pair, so-called ttH production, within the Standard Model schema and beyond is treated. The observation for ttH production with the ATLAS detector recently announced in 2018 represents a significant milestone for the High-Energy Physics field. In order to broaden the spectrum of this ttH analysis beyond the SM, this 4L channel final states was also studied in the context of the search for doubly charged Higgs boson decaying into W±W±, H±±→W±W±.In conclusions, future prospects in Standard Model (SM) as well as Beyond SM (BSM) scientific results that could be reached using the full Run1 and Run2 combined available statistics are given
43
Santos, Alexander Lunkes dos. "Matéria escura como uma extensão Higgs-Stueckelberg do modelo padrão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/130087.
Full textAbstract:
Partículas massivas fracamente interagentes (WIMPs) são um dos mais atrativos candidatos para a matéria escura. Tais partículas são também muito promissoras em termos de detecção direta e indireta, pois elas devem possuir alguma conexão com as partículas do Modelo Padrão. Nesse contexto, extensões do Modelo Padrão podem introduzir candidatos para essas partículas de matéria escura. Propomos um modelo de extensão dupla para descrever as WIMPs, também chamadas de partículas escuras. Essa extensão é feita adicionando dois grupos de simetrias de calibre U(1) ao Modelo Padrão, um via mecanismo de Stueckelberg e o outro via mecanismo de Higgs. O mecanismo de Stueckelberg é um dos caminhos para garantir a invariância de calibre em bósons vetoriais massivos. Então, obtemos dois novos bósons de calibre, um chamado Z′ que é massivo e o outro γ′ (fóton escuro), que não possui massa e não interage com partículas do Modelo Padrão. A densidade de relíquia obtida experimentalmente pelas sondas espaciais WMAP e Planck auxilia na obtenção do valor mais provável para a massa do WIMP e, assim, podemos fixar outros parâmetros importantes para o modelo. Fazemos uma estimativa do impacto da presença de matéria escura e, principalmente, da emissão de fótons escuros no resfriamento de anãs brancas e de estrelas de nêutrons. Alguns resultados e perspectivas são apresentados.Weakly interacting massive particles (WIMPs) are one of the most attractive candidates for dark matter. Such particles also are very promising in terms of direct and indirect detection, because they must have some connection to Standard Model (SM) particles. In this context, extensions of the SM can introduce candidates for these dark matter particles. In this sense, we propose a double extension model to describe the weakly interacting massive particles (WIMPs) or sometimes called dark particles. This extension is done by adding two extra U(1) gauge groups to the Standard Model, one via Stueckelberg mechanism and the other via Higgs mechanism. The Stueckelberg mechanism is one of the ways to ensure gauge invariance . Then we get two new gauge bosons, one called Z′ which is massive and the other γ′ (dark photon), which is massless and does not interact with the Standard Model particles. The relic density experimentally obtained by the WMAP and Planck spacecrafts will help in getting the most likely value for the mass of the WIMP and we can thus set other important parameters for the model. We estimate the impact of the presence of dark matter, and especially dark photon emission, in the cooling of white dwarfs and neutron stars. Some results and perspectives are presented.
44
Thompson, David Ian. "Low energy consequences of some non-standard Higgs models." Connect to e-thesis, 2007. http://theses.gla.ac.uk/143/.
Full textAbstract:
Thesis (Ph.D.) - University of Glasgow, 2007.Ph.D. thesis submitted to the Department of Physics and Astronomy, Faculty of Physical Sciences, University of Glasgow, 2007. Includes bibliographical references. Print version also available.
45
Casolino, Mirkoantonio. "Searches for new phenomena involving top quarks and Higgs bosons with the ATLAS detector." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/402251.
Full text
46
Michaut, Marine. "Recherche de bosons de Higgs supersymétriques au Tevatron dans l'expérience D0." Paris 11, 2006. http://www.theses.fr/2006PA112208.
Full textAbstract:
Une recherche des bosons de Higgs neutres de l'extension supersymétrique minimale du modèle standard est effectuée dans les canaux à trois ou quatre jets, p antip -> Phi(-> b antib) b(antib) avec Phi = h, H ou A. Pour se faire, les données enregistrées dans le détecteur D0 auprès du Tevatron entre 2002 et 2006 pour des énergies dans le centre de masse de 1. 96 TeV sont analysées\Une attention particulière est portée sur le déclenchement (optimisation et calcul d'efficacités), ainsi que sur la méthode d'analyse. Des méthodes sont mises au point pour réaliser l'analyse en minimisant l'utilisation des simulations. L'analyse des données, effectuée avec 0. 9 fb-1, n'a pas permis de mettre en évidence un excès révélant la présence d'un signal. Cela conduit à contraindre l'espace des paramètres de l'extension supersymérique minimale du modèle standard. Les limites suivantes à 95 % de niveau de confiance sont établies : tan beta > 46-121 pour m_Phi = 100-170 GeVA search for the neutral Higgs bosons of the minimal supersymmetric extension of the standard model is performed in the three or four jets channels, p antip -> Phi(-> b antib) b(antib) witth Phi = h, H or A. For this purpose, the data collected with the D0 detector from 2002 to 2006 at hadronic collider Tevatron with a center of mass energy of 1. 96~TeV are analyzed. A complete study of the triggering is first done. The triggering conditions are optimized in order to keep the more signal fraction possible. Furthermore, a method is developped to predict the triggering efficiencies on our signal and backgrounds using only the data. Then an analysis method that allows to predict our background without the help of simulations is studied. No excess of events is observed in the data sample analyzed, corresponding to an integrated luminosity of 0. 9 fb-1, so limits are set in the minimal supersymmetric extension of the standard model. At 95 % CL, the following limits are found : tan beta > 46-121 for m_Phi = 100-170 GeV
47
Fisk, Ian Michael. "Search for neutral Higgs Bosons in electron positron interactions at 189GeV /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9961761.
Full text
48
Hoffmann, Malte [Verfasser], and Peter [Akademischer Betreuer] Schleper. "Search for the decay of a heavy Higgs boson decaying to two light Higgs bosons using a kinematic fit / Malte Hoffmann ; Betreuer: Peter Schleper." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1122482221/34.
Full text
49
Machado, Ana Carolina Bruno [UNESP]. "Resolvendo o problema dos sabores." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/102497.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:32:09Z (GMT). No. of bitstreams: 0
Previous issue date: 2011-08-19Bitstream added on 2014-06-13T20:23:06Z : No. of bitstreams: 1
machado_acb_dr_ift.pdf: 714100 bytes, checksum: 7b80564011cbcd6e5a4857316583f95b (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Neste trabalho, propomos duas extensões multi-Higgs do modelo padrão com simetrias discretas abelianas e não abelianas e com o setor escalar que possui pelo menos um dubleto de Higgs para cada férmion do MP. Mostramos que do ponto de vista fenomenológico os modelos concordão com os dados experimentais e as massas e as matrizes de mistura CKM e PMNS são corretamente obtidas, para o primeiro modelo que descreve o setor dos quarks e dos léptons e para o segundo modelo, que descreve somente o setor dos léptons a matriz de mistura PMNS e as massas são devidamente obtidas
In this work we propose two multi-Higgs extension of the Standard Model with Abelian and non Abelian discrete symmetries and a scalar sector which has at least one Higgs doublet for each fermion of the Standard Model. From the phenomenological point of view the models are safe and the masses and the mixing matrices CKM and PMNS are properly obtained for the first model that describes the sector of quarks and leptons. The second model describes only the leptonic sector, but the mixing matrix and masses are also obtained in compliance with the experimental data
50
Alves, Alexandre. "Procura de nova física em anéis de colisão hadrônicos /." São Paulo, 2004. http://hdl.handle.net/11449/132743.
Full textAbstract:
Orientador: Oscar José Pinto ÉboliBanca: Sérgio Ferraz Novaes
Banca: Rogério Rosenfeld
Banca: Alberto Franco de Sá Santoro
Banca: Orlando Luis Goulart Peres
Resumo: A procura por nova física em escala subatômica em anéis de colisão hadrônicos em dois cenários de grande interesse fenomenológico - o setor de quebra espontânea de simetria e a extensão com quebra de paridade R do MSSM - é apresentada nesta tese. Na primeira parte da tese, mostramos que extensões do Modelo Padrão ou do MSSM que incorporem um setor de quebra espontânea de simetria complexo, contendo um número arbitrário de dubletos e singletos de escalares de 'SU(2) IND. L' podem ser facilmente estudados no Large Hadron Collider (LHC) do CERN através do processo de fusão de bósons fracos com o subsequente decaimento em léptons. Cerca de 10 'fb POT. -1' a 50 'fb POT. -1' de luminosidade integrada serão necessários para se obter um sinal de 5'sigma' de significância estatística. Mostramos também que a distribuição de massa transversa dos bósons fracos pode ser usada para se distinguir o caso de um modelo contínuo de bósons de Higgs em relação ao caso do Modelo Padrão, contudo, o processo de fusão de glúons com o mesmo canal de decaimento dos bósons de Higgs pode ser mais promissor neste sentido. Na segunda parte da tese, calculamos as correções completas de Next-to-Leading-Order de SUSY-QCD à produção associada de stops/sbottoms e léptons no Tevatron e no LHC no âmbito do MSSM estendido por interações com quebra de paridade R. As correções de NLO aumentam as seções de choque totais em até 70%(50%) no Tevatron (LHC), ao mesmo tempo que reduzem a incerteza teórica relacionada à escolha das escalas de renormalização e fatorização. Desacoplando o espectro pesado de SUSY, mostramos que o alcance de procura do Tevatron e do LHC por leptoquarks escalares, que se acoplam a quarks up e down e que decaiam exclusivamente em quarks e léptons, pode ser aumentado usando-se as seções de choque de NLO. No caso do Tevatron, leptoquarks de massas até 310 GeV podem...
Abstract: We present the search for new physics at subatomic scales at hadron colliders in two important phenomenological scenarios -- the spontaneous symmetry breaking sector and the R-parity violating extension of the MSSM. In the first part of this thesis, we show that extensions of the Standard Model and the MSSM, which embody a complex spontaneous symmetry breaking sector containing an arbitrary number of 'SU(2) IND. L' escalar doublets and singlets, can be easily studied at the LHC in the weak boson fusion process with the subsequent decay to leptons. About 10 'fb POT. -1' a 50 'fb POT. -1' of integrated luminosity will be necessary in order to get a 5'sigma' level signal. We also show that the weak bosons' transverse mass distributions can be used to distinguish the continuum model from the Standard Model case, however, the gluon fusion process in the same decay channel may be more promising in this regard. In the second part of the thesis, we compute the full NLO SUSY-QCD corrections to the stop/sbottom lepton associated production at the Tevatron and at the LHC in the MSSM framework extended by R-parity breaking couplings. The NLO correc- tions increase the total cross sections up to 70%(50%) at the Tevatron(LHC) and reduce the theoretical uncertanties related to the choice of the renormalization and factorization scales. Decoupling the heavy SUSY spectrum, we show that the search reach of the Tevatron and the LHC for scalar leptoquarks, which couple to up and down quarks and decay exclusively to quarks and leptons, increases using the NLO rates. For the Tevatron, leptoquarks of masses up to 310 GeV can be excluded to 95% C.L., while for the LHC, leptoquarks of masses up to 3.1 TeV can be excluded at the same statistical level
Doutor