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Hamada, Yuta. "Higgs potential and naturalness after the Higgs discovery." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215312.
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Gu, Jiayin, Honglei Li, Zhen Liu, Shufang Su, and Wei Su. "Learning from Higgs physics at future Higgs factories." SPRINGER, 2017. http://hdl.handle.net/10150/626569.
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Future Higgs factories can reach impressive precision on Higgs property measurements. In this paper, instead of conventional focus of Higgs precision in certain interaction bases, we explore its sensitivity to new physics models at the electron-positron colliders. In particular, we study two categories of new physics models, Standard Model (SM) with a real scalar singlet extension, and Two Higgs Double Model (2HDM) as examples of weakly-interacting models, Minimal Composite Higgs Model (MCHM) and three typical patterns of the more general operator counting for strong interacting models as examples of strong dynamics. We perform a global fit to various Higgs search channels to obtain the 95% C.L. constraints on the model parameter space. In the SM with a singlet extension, we obtain the limits on the singlet-doublet mixing angle sin theta, as well as the more general Wilson coefficients of the induced higher dimensional operators. In the 2HDM, we analyze tree level effects in tan beta vs. cos(beta-alpha) plane, as well as the one-loop contributions from the heavy Higgs bosons in the alignment limit to obtain the constraints on heavy Higgs masses for different types of 2HDM. In strong dynamics models, we obtain lower limits on the strong dynamics scale. In addition, once deviations of Higgs couplings are observed, they can be used to distinguish different models. We also compare the sensitivity of various future Higgs factories, namely Circular Electron Positron Collider (CEPC), Future Circular Collider (FCC)-ee and International Linear Collider (ILC).
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Schildt, Erik. "Higgs inflation." Thesis, Uppsala universitet, Teoretisk fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355063.
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In this project a recent model of inflation in which the Standard Model Higgs field with a nonminimal coupling to gravity takes on the role of the inflaton field is investigated. The tensor to scalar ratio, spectral index and the running of the spectral index is calculated for a tree level analysis and compared with the Planck experiment. The value of the nonminimal coupling constant $\xi$ is estimated by obtaining a relation between the amplitude of scalar perturbations and the Higgs mass, it is found that $\xi \sim 10^4$. The basic aspects of how the results are modified through quantum corrections and what the consequences of the nonminimal coupling are for the effective field theory description is discussed. It is found that a tree level analysis yields predictions which are inside the allowed regions of the cosmological parameters given by the Planck experiment. The large value of the nonminimal coupling leads to unitarity problems for this model of inflation. However quantum effects will have a significant effect and how they modify the results of the tree level analysis is what decides if Higgs inflation is a viable theory.I detta projekt undersöker vi en modell av kosmisk inflation där Higgsfältet med en ickeminimal koppling till tyngdkraften är mekanismen bakom inflation. Vi utför en klassisk analys och beräknar modellens föresägelser för ett antal kosmologiska parametrar som jämförs med Planck experimentet. Vi uppskattar värdet på den ickeminimala kopplingen $\xi$ och finner att $\xi \sim 10^4$. De grundläggande aspekterna bakom kvantanalysen samt vad effekten av den ickeminimala kopplingen har på beskrivningen i termer av en effektiv fältteori diskuteras. Vi finner att en klassisk analys ger förutsägelser som passar väl med Planckexperimentet men att den ickeminimala kopplingen leder till unitaritetsproblem för denna modell av inflation. Kvanteffekter kan dock ha en avsevärd effekt på resultat och en utförlig analys som tar dem till hänsyn krävs för att avgöra om Higgsinflation är en möjlig modell för inflation.
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Kling, Felix, and Felix Kling. "Exotic Higgs Decays." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/620861.
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Many models of physics beyond the Standard Model include an extended Higgs sector, responsible for electroweak symmetry breaking, and predict the existence of additional Higgs bosons. The Type II Two-Higgs-Doublet Model (2HDM) is a particularly well motivated scenario and a suitable framework for phenomenological studies of extended Higgs sectors. Its low energy spectrum includes two CP-even Higgses h and H, one CP-odd Higgs A, and a pair of charged Higgses H±. We study the implication of the LHC Higgs search results on the Type II 2HDM and identify regions of parameter space which are consistent with all experimental and theoretical constraints and can accommodate the observed 125 GeV Higgs signal. This includes parameter space with a distinctive mass hierarchy which permit a sizable mass splitting between the undiscovered non-Standard Model Higgs states. If this mass splitting is large enough, exotic Higgs decay channels into either a Higgs plus a Standard Model gauge boson or two lighter Higgses open up. This can significantly weaken the reach of the conventional Higgs decay channels into Standard Model particles but also provide the additional opportunity to search for exotic Higgs decay channels. We provide benchmark planes to explore exotic Higgs decay scenarios and perform detailed collider analyses to study the exotic decay channels H/A -> AZ/HZ and H± -> AW/HW. We find that these exotic decays offer complementary discovery channels to the conventional modes for both neutral and charged Higgs searches and permit exclusion and discovery in large regions of parameter space.
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Akeroyd, Andrew Gerard. "Signals of non-minimal Higgs sectors at future colliders." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5288/.
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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.
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Lowe, A. P. "Lattice gauge-Higgs theories." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378268.
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You, Tiann-Tevong. "Characterising the Higgs Boson." Thesis, King's College London (University of London), 2016. https://kclpure.kcl.ac.uk/portal/en/theses/characterising-the-higgs-boson(1ca43424-ea36-4bc6-be29-ac9e306249fe).html.
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On July 2012 the ATLAS and CMS collaborations announced the historic discovery of a Higgs boson at the CERN Large Hadron Collider. A remarkable century exploring Nature's sub- atomic constituents led to the Standard Model (SM) of particle physics with the Higgs as the last missing piece. In this thesis we review the construction of this theory and its experimental successes, focusing on the Higgs sector responsible for electroweak symmetry breaking and providing mass to matter and force particles. The de ning signature of a Higgs particle is that of a scalar coupling proportionally to mass. We show how early data suggests indirectly that the observed particle has spin zero, and propose a method for directly measuring the spin using an invariant mass distribution of the Higgs produced in association with a vector boson. We also perform a global analysis of its couplings before and after the discovery, testing the expected mass-proportionality and constraining models in which the Higgs may be composite or even another scalar entirely, such as a pseudo-dilaton. In the absence of any signi cant deviations from the properties of the SM Higgs boson, the SM is then treated as an e ective eld theory (EFT) assuming new physics beyond the SM (BSM) is decoupled at higher energies. The leading lepton-number-conserving operators arise at the dimension-6 level, parametrised by their Wilson coecients. These are constrained by their e ects in Higgs physics, triple-gauge coupling measurements, and electroweak precision tests. The coecients may also be calculated in a speci c BSM theory by integrating out heavy particles. We illustrate this in the case of stops and sbottoms in the minimally supersymmetric SM, using the covariant derivative expansion method and generalising the universal one-loop e ective Lagrangian in the process. Finally the potential for discovering BSM physics at future colliders is investigated. We conclude with a summary and outlook on prospects for the future.
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Blaavand, Jakob Lindblad. "The Dirac-Higgs bundle." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:6e081810-f042-4b3e-9f7c-9eee3c930c35.
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The Dirac-Higgs bundle is a vector bundle with a natural connection on the moduli space of stable Higgs bundles on a compact Riemann surface. It is a vector bundle of null-spaces of a Dirac-operator coupled to stable Higgs bundles. In this thesis, we study various aspects of this bundle and its natural connection. The Dirac-Higgs bundle is hyperholomorphic on the smooth hyperkähler moduli space of stable Higgs bundles. This property is a generalisation of the four-dimensional anti- self-duality equations to hyperkähler manifolds. One use of the Dirac-Higgs bundle is the construction of a Nahm transform for Higgs bundles. This transform produces hyperholo- morphic bundles on the moduli space of rank one Higgs bundles. The Higgs bundle moduli space is non-compact and we study the asymptotics of the connection in the Nahm transform of a Higgs bundle. We show that elements of the null- spaces concentrate at a finite number of points on the Riemann surface. This asymptotical behaviour naturally defines a frame for the Nahm transform, which is conjectured to be asymptotically unitary. By considering only the holomorphic structure, the Nahm transform of a Higgs bundle extends to a holomorphic bundle on the natural compactification of the rank one Higgs bundle moduli space. We discuss various aspects of this extended holomorphic bundle. Most importantly, it is a sheaf extension in which the constituent sheaves and the extension class have natural interpretations in terms of the original Higgs bundle. Furthermore, the extended bundle is not fixed at the divisor at infinity; explicit examples show that it depends on the type of Riemann surface, for example. The Dirac-Higgs bundle has a parabolic cousin. In the parabolic case the rank depends on the number of marked points and the total multiplicity of the zero weights in the parabolic structure. The moduli space of stable rank two parabolic Higgs bundles on the Riemann sphere with four marked points has complex dimension two. Furthermore, there is a combination of parabolic weights such that the Dirac-Higgs bundle is a line bundle with an instanton connection. We study the topology of this line bundle and find that the instanton does not have finite energy. As in the non-parabolic case we define a Nahm transform for parabolic Higgs bundles, and in the case of genus one Riemann surfaces use it to produce doubly-periodic instantons of finite energy.
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Braathen, Johannes. "Automating Higgs precision calculations." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS073/document.
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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
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Kallarackal, Jim. "The Higgs boson resonance from a chiral Higgs-Yukawa model on the lattice." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16332.
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Das Higgs-Teilchen ist essentiell für die Erzeugung von Massen für Fermionen und Eich- bosonen der schwachen Wechselwirkung. Ziel dieser Arbeit ist es, die Masse und die Zerfallsbreite des Higgs-Teilchens einzugrenzen. Grundlage für die Berechnung physikalischer Größen ist dabei das Pfadintegral, welches mittels Monte-Carlo Simulationen bestimmt wird. Ein polynomieller Hybrid-Monte- Carlo-Algorithmus berücksichtigt dabei alle dynamischen Freiheitsgrade der Fermionen. Die chirale Natur der Fermionen werden mit Hilfe des Neuberger- Overlap-Operators beschrieben. In dieser Arbeit wird das Standardmodell auf den Higgs-Yukawa-Sektor eingegrenzt, welcher keine Eichbosonen enthält und lediglich ein degeneriertes Quark-Doublet berücksichtigt. Anhand des Higgs-Teilchen-Propagators werden die Ergebnisse aus der Git- terstörungsrechnung bis zu einer Schleife mit denen aus der Monte-Carlo- Simulation verglichen. Für die untersuchten Parameter, stimmen die Ergeb- nisse aus der Störungstheorie mit den Monte-Carlo-Daten sehr gut überein. Ein Schwerpunkt dieser Arbeit ist die Analyse der Resonanzparameter des Higgs-Teilchens. Die Resonanzmasse und die Resonanzbreite werden bei schwachen als auch bei starken quartischen Kopplungen untersucht. Das Higgs-Teilchen erscheint nicht als asymptotisch stabiles Teilchen, sondern als Resonanz. In allen Fällen liegt die Resonanzbreite unter 10% der Resonanzmasse. Die Resonanzmasse wird sodann mit der Propagatormasse verglichen. Für alle betrachteten Kopplun- gen gibt es eine hervorragende Übereinstimmung beider Größen. Zuletzt gilt es, den Einfluss einer schweren vierten Generation von Quarks auf die obere und untere Massenschranke des Higgs-Teilchens zu untersuchen. Alle numerischen Resultate involvieren eine umfassende Analyse der Volu- menabhängigkeit und erfordern zwingend eine Extrapolation ins unendliche Volumen.The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for fermions and the weak gauge bosons. The goal of this work is to set limits on the mass and the decay width of the Higgs boson. The basis to compute the physical quantities is the path integral which is here evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. A polynomial hybrid Monte Carlo algo- rithm is used to incorporate dynamical fermions. The chiral symmetry of the electroweak model is incorporated by using the Neuberger overlap operator. Here, the standard model is considered in the limit of a Higgs-Yukawa sector which does not contain the weak gauge bosons and only a degenerate doublet of top- and bottom quarks are incorporated. Results from lattice perturbation theory up to one loop of the Higgs boson propagator are compared with those obtained from Monte Carlo simulations. At all values of the investigated couplings, the perturbative results agree very well with the Monte Carlo data. A main focus of this work is the investigation of the resonance parameters of the Higgs boson. The resonance width and the resonance mass are investigated at weak and at large quartic couplings. The Higgs boson does not appear as an asymptotic stable state but as a resonance. In all considered cases the Higgs boson resonance width lies below 10% of the resonance mass. The obtained resonance mass is compared with the mass obtained from the Higgs boson propagator. The results agree perfectly at all values of the quartic coupling considered. Finally, the effect of a heavy fourth generation of fermions on the upper and lower Higgs boson mass bound is studied. All numerical results presented in this work involve extensive finite volume analysis and an extrapolation to infinite volume is inevitable.
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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.
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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).
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Le, Corre Solen. "Higgs boson phenomenology beyond the Standard Model." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1028.
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Suite à la découverte du boson de Higgs en Juin 2012 au Large Hadron Collider, l’accélérateur de particules situé à la frontière franco-suisse, l’étude du secteur scalaire des particules élémentaires a connu un regain d’intérêt. En particulier, le boson de Higgs étant une particule clef au sein du Modèle Standard des particules, les expérimentateurs étudient ses propriétés avec beaucoup de soin.Le Modèle Standard, dont le but est de décrire les interactions entre particules élémentaires, n’est cependant pas une théorie complète. En effet, en plus de quelques problèmes d’ordre théorique, certains phénomènes observés expérimentalement ne peuvent pas être expliqués par ce modèle. Les théoriciens en physique des particules cherchent donc à établir une nouvelle théorie venant le compléter et permettant d’expliquer pleinement les observations expérimentales.Cette thèse est axée sur l’étude du secteur scalaire de modèles au-delà du Modèle Standard des particules. J’ai plus particulièrement travaillé sur un modèle à deux doublets de Higgs – modèle purement effectif mais qui peut être inclus dans d’autres théories plus abouties – ainsi que sur un modèle construit comme une combinaison entre les théories déjà très proches de techicouleur et de Higgs composites, et ce dans le cas particulier d’une brisure de symétrie SU (4) ? Sp(4). J’ai étudié ce dernier modèle d’un point de vue effectif mais la théorie complète est capable depallier un certain nombre des limitations du Modèle Standard.Chacun de ces modèles inclut un secteur scalaire plus riche que celui du Modèle Standard et contient au moins une particule pouvant être assimilée au boson de Higgs découvert au LHC. J’ai réalisé l’étude phénoménologique de chacun de ces modèles et les ai confrontés à des contraintes tant théoriques qu’expérimentales – en particulier celles obtenues grâce aux études les plus récentes, portant sur le boson de Higgs et sur de potentielles particules scalaires additionnelles, réalisées par les équipes du LHC. Cela m’a permis de contraindre les paramètres libres des modèles et en particulier de restreindre les valeurs possibles pour la masse des autres particules scalaires, permettant de mieux cibler les zones où ces nouvelles particules, si elles existent, pourraient être détectées au LHC.Ces deux théories, bien que très contraintes par les données expérimentales, ne sont toujours pas exclues par les contraintes expérimentales les plus récentesFollowing the discovery of the Higgs boson in June 2012 at the Large Hadron Collider, the particle collider located beneath the France-Switzerland border, interest in the study of the scalar sector in elementary particle physics significantly increased. In particular, as the Higgs boson plays a very special role in the Standard Model of particle physics, experimentalists study its properties with great care.The goal of the Standard Model is to describe the interactions between elementary particles. However the theory is not quite complete. Indeed, in addition to some purely theoretical problems, a number of experimental observations cannot be explained by the Standard Model. Theorists are therefore looking for a more comprehensive theory able to fully explain the observations.This thesis is based on the study of the scalar sector of two different extensions of the Standard Model of particle physics. I have worked on the Two-Higgs Doublet Model – this model is purely effective but can be included in more comprehensive theories – as well as on a model based on a combination of Technicolor and Composite Higgs theories in the framework of the SU (4) ? Sp(4) symmetry breaking pattern. I studied the latter via an effective approach but the full theory is able to get rid of some of the pitfalls of the Standard Model.These two models include a scalar sector that is richer than the one found in the Standard Model and contain at least one particle which can be assimilated to the Higgs boson discovered at the LHC.I performed a phenomenological study for these two models and tested them against both theoretical and experimental constraints. In particular I used the latest studies on the 125 GeV Higgs boson and on possible additional scalars performed by the ATLAS and CMS collaborations. The application of all these constraints drastically reduced the available parameter space of the two models. In particular it narrowed the possible mass range of the additional scalars, allowing to know more accurately where to search them experimentally in order to prove or rule out their possible existence.As of today the two theories I worked on are still not excluded by the latest experimentaldata
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Lietti, S. M. (Sérgio Morais). "Lagrangeanas efetivas e acoplamentos anômalos do bóson de Higgs /." São Paulo, 1998. http://hdl.handle.net/11449/132812.
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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
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Saadi, Hassan. "Dilaton as the Higgs particle." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/60177.
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This essay focuses on exploring dilatons as an alternate model to the Higgs mechanism. An introductory analysis to the Higgs mechanism, effective potential method, and dilatons is provided. Then, three different models are explored on how to obtain a light dilaton that emerges as a pseudo Goldstone boson because of the spontaneously broken approximate scale invariance. This light dilaton is shown to have properties that are, in general, similar to the Higgs boson with minor differences that can differentiate between the two models in collider experiments.Science, Faculty of
Mathematics, Department of
Graduate
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Rayan, Steven. "Geometry of co-Higgs bundles." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543002.
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Patt, Brian Lawrence. "Higgs family symmetry and supersymmetry." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36397.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 77-79).
In this thesis we investigate building models of family symmetry that give the Higgs fields family structure. We construct several models, starting with 2 generation models then moving onto 3 generation models. These models are described sequentially in chapters 2 through 6. All of these models are supersymmetric and they did not previously exists in the literature. In these models, quark (and lepton) masses and mixings are determined the vacuum expectation values of the family sector. These vacuum expectation values (VEV) can have a hierarchal structure because they correspond to flat directions of a superpotential. At low energies these models contain just one light pair of Higgs fields. Experimentally, the most interesting feature of these models are couplings between the low energy Higgs and moduli of the family sector. These couplings should be observable at the Large Hadron Collider.
by Brian Lawrence Patt.
Ph.D.
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Guardado, Karla (Karla M. ). "Preheating in new Higgs inflation." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100337.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 37-38).
Cosmological inflation describes the phenomenon in the early universe when spacetime underwent a rapid, exponential expansion right after the Big Bang. Inflation solves the so-called "horizon problem," "flatness problem," and "monopole problem" of standard Big Bang cosmology. Furthermore, New Inflation solves the "graceful exit problem" of the original theory. In inflation, the energy density of a patch of the early universe becomes dominated by the potential energy of a scalar field in a state of false vacuum. This particular form of energy leads to a negative pressure, creating a repulsive gravitational force, driving the region into a period of exponential expansion. Soon after the end of inflation, the field oscillates, leading to the creation of particles in a process called reheating. If reheating begins with parametric resonance, the process is called preheating. New Higgs Inflation presumes that the Higgs field is the scalar field in question, involving a characteristic non-minimal "derivative" coupling. The equation of motion for the field evolves like a damped harmonic oscillator, so we expect it to oscillate near the end of inflation. We study the dynamics of the Higgs field during and after inflation and find that preheating should be efficient in this model.
by Karla Guardado.
S.B.
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Kwong, Kam-Yuen. "Quantum induction and Higgs mass." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289767.
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With our newly proposed dynamical Higgs mechanism and Quantum Induction programme, Higgs mass is predicted at M(H) ≈ 190 GeV by using our modified renormalization group equations. The same procedure also explains the top quark mass correctly.
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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.
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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.
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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.
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Charfeddine, Driss. "Etude du bruit de fond du canal H->ZZ->4l dans l'expérience ATLAS du LHC et recherche au-delà du modèle standard par le modèle à deux doublets de Higgs." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01000000.
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Le boson de Higgs, qui est responsable de la brisure de symétrie électrofaible et de l'origine de la masse des particules, est le sujet central de la physique des particules d'aujourd'hui. J'ai travaillé sur le boson de Higgs se désintégrant en quatre leptons dans l'expérience ATLAS du LHC.Dans ma thèse, j'ai étudié le bruit de fond du canal H->ZZ^*->4l. Le signal de ce canal est très propre car il a quatre leptons dans l'état final. Il est donc important de maitriser son bruit de fond afin d'extraire le signal. J'ai travaillé à la réduction d'une des principales sources de bruit de fond: Z+ee->4leptons.En fin de thèse j'ai étudié un modèle au-delà du Modèle Standard: le modèle à deux doublets de Higgs (2HDM). Dans cette étude nous supposons que le boson de Higgs légers à la masse de la nouvelle particule détectée au LHC : 125 GeV. Aucun signal n'a été trouvé pour le boson de Higgs lourd et les limites sont données dans l'espace des paramètres de 2HDM.
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Elias, Miró Joan. "Theoretical Implications of the Higgs Discovery." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/311621.
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El reciente descubrimiento de la partícula Higgs en el Large Hadron Collider (LHC) es un hito en la física de partículas. Dicho descubrimiento abre la posibilidad de explorar el Standard Model (SM) y posible nueva física más alla del SM (BSM, i.e. beyond the SM ) a través de las interacciones del Higgs con las demás partículas del SM. Es decir, el interés real no consiste en el mero hecho de explorar los aspectos puramente fenomenol´gicos del Higgs y del SM sino en entender cual es la física y principios detrás de la rotura de la fuerza electrodébil. La física del Higgs tiene lugar a la escala de energía más alta explorada hasta la fecha y es por lo tanto muy importante que la investiguemos a fondo.
En la primera parte de la tesis discuto las implicaciones que tiene el valor de la masa del Higgs para la estabilidad del vacío electrodébil. En primer lugar, presento el análisis de orden N 2LLog del potencial del Higgs del SM. Este análisis permite reducir a 1 GeV la incertidumbre en el valor crítico de la masa Higgs Mh para la estabilidad del vacío electrodébil. Aunque el parametro del acoplo cuártico del Higgs evaluado en la escala de energía de Planck es muy próximo a zero, el N 2LLog análisis muestra que la estabilidad absoluta del vacío electrodébil es incompatible con los valores centrales de las medidas experimentales de las masas del Higgs y top quark. También muestro que un escalar pesado puede inducir una corrección relativamente grande al acoplo cuártico de Higgs y por lo tanto estabilizar el vaco electrodébill. Varios ejemplos relevantes de física BSM donde el mecanismo puede estar operativo son discutidos.
En la segunda parte de la tesis discutimos como operadores de dimensión superior, que parametrizan física BSM pesada, afecta las interacciones del Higgs. Bajo ciertas asump-ciones, 8 CP-par y 3 CP-impart Wilson coefficients parametrizan el impacto principal en la física del Higgs, ya que todos los demás Wilson coefficients están constre˜nidos por experimentos previos al LHC. Calculamos las dimensiones anómalas más relevantes para la física del Higgs. Esta dimensiones anómalas describen como se mezclan los operadores de dimension superior bajo correcciones cuánticas perturbativas. Esto permite encontrar las correcciones logarítmicas principales a las predicciones de las interacciones del Higgs en varios modelos específicos como el MSSM o el modelo del Higgs compuesto. Tales correcciones pueden ser relevantes en varios casos.
Finalmente, en la última parte estudiamos el patrón sorprendente que tienen las dimen¬siones anómalas de los operadores de dimensión seis. El patrón consiste en que la matriz de dimensiones anómalas presenta muchas entradas nulas, lo cuál no es evidente ya que aparentemente dichas entradas no esta prohibidas por ninguna simetría. Un argumento, basado en el uso de supersimetría como simetría espúrea, es presentado.The discovery of the Higgs at the Large Hadron Collider has triggered a renewed inte- rest on understanding the physical mechanism behind electroweak symmetry breaking. The Higgs boson has opened a new window to probe possible new physics Beyond de Standard Model (BSM) through the measurements of its couplings and its mass value. The Higgs physics is the current energy frontier and it is therefore very important that we explore it thoroughly. In the rst part of the thesis we discuss the implications of the Higgs mass value Mh for the stability of the electroweak (EW) vacuum. We present the next-to-next-to-leading order analysis of the Standard Model Higgs potential. This analysis allows to reduce the theoretical uncertainty in the determination of the critical value of Mh for stability of the EW vacuum to 1 GeV. While the Higgs quartic coupling at the Planck scale is remarkably close to zero, absolute stability of the EW vacuum is excluded for the central experimental values of the Higgs and top quark masses. Next, we show that a heavy scalar singlet can induce a relatively large and positive tree-level threshold correction to the Higgs quartic coupling and stabilize the EW vacuum. We provide examples, such as the see-saw and the invisible axion, where the proposed mechanism is automatically implemented. In the second part we investigate how dimension-six operators, parametrizing heavy BSM physics, a ect the Higgs couplings. Under certain well-motivated assumptions, we nd that 8 CP-even plus 3 CP-odd Wilson coe cients parametrize the main impact in Higgs physics, as all other coe cients are constrained by non-Higgs SM measurements. We calculate the most relevant anomalous dimensions for these Wilson coe cients, which describe operator mixing from the heavy BSM scale down to the EW scale. This allows us to nd the leading-log corrections to the predictions for the Higgs couplings in speci c models, such as the MSSM or composite Higgs, which we nd to be signi cant in certain cases. Finally, in the third part we study the striking structure of the dimension-six anomalous dimension matrix. We present an argument, partly based on the use of supersymmetry as a spurious symmetry, that gives an explanation to the plethora of vanishing entries in the anomalous dimension matrix that are not forbidden by symmetries otherwise.
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Lee, Jae Yong. "The little Higgs and some phenomenology /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9645.
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Bonsdorff, Juhani. "A Fourier transform for Higgs bundles." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249510.
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Quevillon, Jérémie. "Higgs Physics Beyond the Standard Model." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01070196.
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On the 4th of July 2012, the discovery of a new scalar particle with a mass of order 125 GeV was announced by the ATLAS and CMS collaborations. An important era is now opening: the precise determination of the properties of the produced particle. This is of extreme importance in order to establish that this particle is indeed the relic of the mechanism responsible for the electroweak symmetry breaking and to pin down effects of new physics if additional ingredients beyond those of the Standard Model are involved in the symmetry breaking mechanism. In this thesis we have tried to understand and characterize to which extent this new scalar field is the Standard Model Higgs Boson and set the implications of this discovery in the context of Supersymmetric theories and dark matter models.In a first part devoted to the Standard Model of particle physics, we discuss the Higgs pair production processes at the LHC and the main output of our results is that they al-low for the determination of the trilinear Higgs self-coupling which represents a first important step towards the reconstruction of the Higgs potential and thus the final verifica-tion of the Higgs mechanism as the origin of electroweak symmetry breaking.The second part is about Supersymmetric theories. After a review of the topics one of our result is to set strong restrictions on Supersymmetric models after the Higgs discov-ery. We also introduce a new approach which would allow experimentalists to efficiently look for supersymmetric heavy Higgs bosons at current and next LHC runs.The third part concerns dark matter. We present results which give strong constraints on Higgs-portal models. We finally discuss alternative non-thermal dark matter scenario. Firstly, we demonstrate that there exists a tight link between the reheating temperature and the scheme of the Standard Model gauge group breaking and secondly we study the genesis of dark matter by a Z' portal.
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Williams, Peter Howard. "Hadronic Higgs production with forward jets." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3131/.
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The production of a Higgs boson with central rapidity, decaying to bb and accompanied by two jets that are forward in rapidity is presented as an important class of events at the Large Hadron Collider. Specifically, we study central Z boson production accompanied by rapidity gaps on either side as a way to gauge Higgs production via weak boson fusion at the LHC. We analyse the possible backgrounds for the bb decay mode and show that these can be substantially reduced. Special attention is paid to the evaluation of the gap survival factor, which is the major source of theoretical uncertainty in the rate of H, Z and W central production events with rapidity gaps. More generally, in relation to Higgs plus forward jet production, we consider the hadronic radiation patterns for the generic process of bb plus two forward jet production at the LHC, where the (centrally produced) bb originate either from a Higgs, a Z or from standard QCD production processes. A numerical technique for evaluating the radiation patterns for non-trivial final states is introduced and shown to agree with the standard analytic results for more simple processes. Significant differences between the radiation patterns for the Higgs signal and the background processes are observed and quantified. This suggests that hadronic radiation patterns could be used as an additional diagnostic tool in Higgs searches in this channel at the LHC. We also study the applicability of an equivalent photon/gluon approximation in describing events with a central system accompanied by two forward jets.
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Pasterski, Sabrina Gonzalez. "Measuring Higgs self-coupling at CMS." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83802.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 43).
This study evaluates the Compact Muon Solenoid (CMS) experiment's ability to characterize Higgs self-coupling through the ... channel. The effective cross-section for detecting ... events is computed by finding the fraction of simulated events that make it through selection cuts. These same cuts also are applied to simulated background samples. The result is then compared to a recent theoretical study on measuring Higgs self-coupling to check the applicability of its assumptions and the feasibility of its predictions. This study finds that the selection algorithms currently used for ... analyses at CMS produce a lower yield of signal events. Since the ... channel was predicted to be one of the most promising for characterizing the Higgs self-coupling constant, ... , the results of this study indicate that, unless the methods for reconstructing detected particles are improved, future data collected by CMS will not be sufficient to complete such an analysis.
by Sabrina Gonzalez Pasterski.
S.B.
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Schaposnik, Laura P. "Spectral data for G-Higgs bundles." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:7b483c4c-53e4-4449-88c2-7a75d98ac861.
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We develop a new geometric method of understanding principal G-Higgs bundles through their spectral data, for G a real form of a complex Lie group. In particular, we consider the case of G a split real form, as well as G = SL(2,R), U(p,p), SU(p,p), and Sp(2p,2p). Further, we give some applications of our results, and discuss open questions.
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Dias, Otávio Augusto Trivério [UNESP]. "Escalares de Higgs e decaimentos leptônicos." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/132575.
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Silva, Paulo José Ferreira Porfírio da. "Modelo de dois dubletos de higgs." Universidade Federal da Paraíba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/5756.
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Previous issue date: 2013-03-07Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this dissertation we did a complete review of the StandardModel(SM), emphasizing the weak interactions, this in order to treat an extension of theMP with addition of a doublet of scalar theory, known in the literature asModel with Two Higgs doublets (2HDM). We will treat this model from the point of view of both aspects: when two doublets develop the expected value of the vacuum(vev) and when only one develops doublets vev, utilize the potential of 2HDM does not violate CP. These two models are particularly important because they are quite simple and can solve some problems that are open in Physics, one of the most important is the dark matter (DM). Furthermore, we will use the formalism of oblique parameters, radiative corrections involving first order, to parameterize the effects of New Physics (NP). We will present the phenomenology to obtain 2HDMI and regions that are in agreement with the experimental data.
Nesta dissertação fizemos uma revisão completa doModelo Padrão (MP), dando ênfase as interações fracas, isto com o intuito de tratarmos de uma extensão do MP com adição de um dubleto de escalar a teoria, conhecida na literatura como Modelo com Dois Dubletos de Higgs(2HDM)1. Iremos tratar deste modelo sob o ponto de vista de dois aspectos: quando os dois dubletos desenvolvem valor esperado do vácuo(vev) e quando apenas um dos dubletos desenvolve vev, utilizamos o potencial do 2HDM que não viola CP. Particularmente, esses dois modelos são importantes porque eles são bastante simples e podemresolver alguns problemas que estão emaberto na Física, um dosmais importantes é amatéria escura(ME). Além disso, iremos utilizar o formalismo de parâmetros oblíquos, que envolve correções radiativas de primeira ordem, para parametrizar os efeitos da Nova Física(NF). Apresentaremos a fenomenologia para o 2HDMI e obteremos as regiões que estão de acordo com os dados experimentais.
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Dias, Otávio Augusto Trivério. "Escalares de Higgs e decaimentos leptônicos /." São Paulo, 2004. http://hdl.handle.net/11449/132575.
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Orientador: Vicente PleitezBanca: Mauro Donizeti Tonasse
Banca: Marcos Cardozo Rodriguez
Resumo: É estudado o decaimento do 'mü'- em dois diferentes modelos com simetrias de gauge 'SU(3) IND. c' X 'SU(3) IND. L' X 'U(1) IND. N'. Estes modelos coincidem com o modelo padrão a baixas energias, prevêem a existência de bósons de gauge bileptônicos e usualmente tem um setor escalar mais rico que o existente no modelo padrão. Fazendo uma redefinição da constante de Fermi, pode ser delimitada a massa do bóson de gauge dileptônico que aparece nos dois modelos e também é delimitada a massa de um escalar de Higgs
Abstract: We consider the 'mü'- leptonic decay in two different gauge models with 'SU(3) IND. c' X 'SU(3) IND. L' X 'U(1) IND. N' gauge symmetries. These models coincide with the standard model at low energies, predict the existence of bileptonic gauge bosons and its scalar sector is richer than the standard model one's. By redefining the Fermi constant, a limit for the bileptonic gauge boson may be set and, in case the new gauge boson is much heavier than the Higgs particle, a limit for the scalar may also be set
Mestre
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Branco, Lucas Castello. "Higgs bundles, Lagrangians and mirror symmetry." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:612325bd-6a7f-4d74-a85c-426b73ff7a14.
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Let Σ be a compact Riemann surface of genus g ≥ 2. This thesis is dedicated to the study of certain loci of the Higgs bundle moduli space. After recalling basic facts in the first chapter about G-Higgs bundles for a reductive group G, we begin the first part of the work, which deals with Higgs bundles for the real forms G0 = SU* (2m), SO* (4m), and Sp(m, m) of G = SL(2m, C), SO(4m, C) and Sp(4m, C), respectively. The second part of the thesis deals with the Gaiotto Lagrangian. Motivated by mirror symmetry, we give a detailed description of the fibres of the G-Hitchin fibration containing generic G0-Higgs bundles, for the real groups G0 = SU* (2m), SO* (4m) and Sp(m, m). The spectral curves associated to these fibres are examples of ribbons, i.e., non-reduced projective C-schemes of dimension one, whose reduced scheme are non-singular. Our description of these fibres is done in two different ways, each giving different and interesting insights about the fibre in question. One of the formulations is given in term of objects on the reduced curve, while the other in terms of the non-reduced spectral curve. A link is also provided between the two approaches. We use this description to give a proposal for the support of the dual BBB-brane inside the moduli space M(LG) of Higgs bundles for the Langlands dual group LG of G. In the second part of the thesis we discuss the Gaiotto Lagrangian, which is a Lagrangian subvariety of the moduli spaces of G-Higgs bundles, where G is a reductive group over C. This Lagrangian is obtained from a symplectic representation of G and we discuss some of its general properties. In Chapter 7 we focus our attention to the Gaiotto Lagrangian for the standard representation of the symplectic group. This is an irreducible component of the nilpotent cone for the symplectic Hitchin fibration. We describe this component by using the usual Morse function on the Higgs bundle moduli space, which is the norm squared of the Higgs field restricted to the Lagrangian in question. Lastly, we discuss natural questions and applications of the ideas developed in this thesis. In particular, we say a few words about the hyperholomorphic bundle, how to generalize the Gaiotto Lagrangian to vector bundles which admit many sections and give an analogue of the Gaiotto Lagrangian for the orthogonal group.
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El, Faham Hesham. "Phenomenological Studies on Composite Higgs Models." Thesis, Uppsala universitet, Högenergifysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-359903.
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Composite Higgs Models (CHMs) are formulated in terms of strongly coupled theories. They often predict fermionic top partners with a mass around the TeV scale. Going beyond minimality enriches the spectrum of the theory with additional hypothetical scalars that significantly change the phenomenology. In this thesis, we explore an SO(6)/SO(5) CHM with an additional pseudo-scalar custodial singlet. The latter has anomalous couplings to the Standard Model vector bosons. We study the phenomenology of the singlet, including bounds from the available ATLAS and CMS searches in the relevant channels with di-boson and fermionic final states. We used HiggsBounds tool to test the model theoretical predictions against the current exclusion limits. The study is performed at the 8 and 13 TeV experiments at the LHC. We present a model parameter space from which the bounds on the (most sensitive) signal cross sections of the hypothetical singlet can be easily extracted.
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Öhman, Henrik. "Analysis of early data from the ATLAS experiment towards H+ searches." Thesis, Uppsala universitet, Högenergifysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-159414.
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In the ATLAS experiment software plays a central role in data taking, reconstruction, and analysis. This thesis presents a set of analysis algorithms written for the ATLAS software framework Athena, towards H+ searches in the τ+jets channel. Data recorded by the ATLAS experiment for 900 GeV proton-proton collisions from 2009 and 7 TeV proton-proton collisions from 2010 are analyzed with these algorithms and compared to Monte Carlo. A search for top quarks is performed on 36 pb-1 of data, and the results are found to agree well with Monte Carlo.
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Spearman, William R. "Measurement of the mass and natural width of the Higgs boson in the H to ZZ to 4l decay channel with the ATLAS detector." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13070058.
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This thesis presents a measurement of the mass, natural width, and signal strength, defined as the yield normalized to the Standard Model prediction, of the Higgs boson in the \(H \rightarrow ZZ^{(*)} \rightarrow 4l\) decay channel using an approach which utilizes event-by-event detector response information. The measurement is performed on p-p collision data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The data corresponds to an integrated luminosity of \(25 fb^{-1}\) with center-of-mass energies of 7 TeV and 8 TeV. The measured mass of the Higgs boson is \(m_H = 124.57_{-0.43}^{+0.48} GeV\). The signal strength was estimated at \(\mu = 1.76_{-0.37}^{+0.46}\). Finally, the natural width of the Higgs was determined to be < 2.6 GeV with 95% confidence. The event-by-event approach used in this analysis involves the parameterization of the behavior of single leptons in the ATLAS detector and the convolution of a mass response with the Higgs truth distribution to derive the reconstruction level signal model.Physics
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Schwoerer, Maud. "'Etudes des états finals diphoton dans l'expérience ATLAS au LHC : mesure de section efficace différentielle, découverte d'une nouvelle résonance dans la recherche du boson de Higgs et étude de ses propriétés'." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00978539.
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Cette thèse sera centrée sur les analyses des événements diphotons dans le détecteur ATLAS. L'activité évoluera au cours du temps et couvrira différents aspects: compréhension de la réponse du détecteur, participation a la prise de données, analyse physique et recherche de signaux de physique au-delà du modèle standard.
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Choudhury, Somnath. "Search for Neutral Higgs Bosons decaying to τ Pairs at the CMS experiment." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112206.
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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
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Almeida, Miquéias Melo de. "Obtenção de um limite para a largura do bóson de Higgs no experimento CMS via H→ ZZ → (4e, 4, 2e2)." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8860.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorApresenta-se neste trabalho um estudo sobre a largura de decaimento total do bóson de Higgs através do canal H→ ZZ → (4e, 4, 2e2). Segundo o Modelo Padrão da Física de Partículas Elementares, um bóson de Higgs com massa de 126 GeV deve ter uma largura de decaimento total ΓH = 4.15 MeV, muito abaixo da resoluções dos experimentos instalados no LHC. Isto impede uma medida direta sobre os eventos da ressonância. Recentemente foi proposto limitar ΓH a partir da relação entre a taxa de eventos observados na região da ressonância e na região off-shell. Utilizando o pacote de análise desenvolvido pela colaboração CMS obteve-se um limite de ΓH < 31.46(12.82) MeV em 95(68.3)% CL combinando os dados coletados pelo LHC em colisões pp em √s = 7 TeV (5.1fb-1) e em √s = 8 TeV (19.7fb -1).
We present in this work a study about the Higgs boson total width using the channel H→ ZZ → (4e, 4, 2e2. According to the Standard Model of Elementary Particle Physics, the Higgs boson with mass around 126 GeV should have a total decay width of ΓH = 4.15 MeV, very below the resolution of the experiments installed at the LHC. This fact prevents a direct measurement on the events of the Higgs resonance. Recently it was proposed limit ΓH from the relationship between the rate of events observed in the resonance and the off-shell regions. Using the package of analysis developed by CMS collaboration was obtained a limit of ΓH < 31.46(12.82)MeV in 95(68.3)% CL combining the data collected by the LHC in pp collisions at √s = 7 TeV (5.1fb-1)and at √s = 8 TeV (19.7fb -1).
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Mahboubi, Kambiz. "ATLAS level-1 jet trigger rates and study of the ATLAS discovery potential of the neutral MSSM Higgs bosons in b-jet decay channels." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961739746.
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Okpara, Anna Nwaada. "Search for charged Higgs bosons at centre of mass energies of 189-209 GeV at LEP." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963720678.
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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.
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Efron, Jonathan Zvi. "Search for the Higgs Boson in the ZH → ℓ+ℓ-bb̄ Channel at CDF Run II." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1189015468.
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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.
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Montull, Garcia Marc. "Higgs Phenomenology and The Hamiltonian Truncation Method." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399334.
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Aquesta tesi està basada en les publicacions fetes com a estudiant de doctorat a l’IFAE en els períodes 2012-2013 i 2015. Aquests estudis inclouen dos temes diferents, fenomenologia del Higgs al LHCk en el marc de models de Higgs Compost i Supersimetria, i la millora del Mètode de Truncació del Hamiltonià Renormalitzat (MTHR).
La primera part de la tesis va ser motivada pel problema de la Naturalitat del Model Estàndard (SM), que es va fer manifest amb el descobriment l’any 2012 d’una partícula escalar amb una massa de 125 GeV i una senyal pels acoblaments compatible amb el Higgs del SM. L’objectiu d’aquests projectes era valorar l’impacte de la massa i senyal dels acoblaments mesurats en les dues extensions del SM més motivades per solventar el problema de la Naturalitat; aquests són models de Higgs Compost i models Supersimetrics. Aquesta part de la tesis està organitzada de la següent forma:
En el Capítol 1 fem una breu introducció al Model Estàndard, les seves limitacions i motivem la necessitat d’anar a física més enllà del Model Estàndard (BSM). També incloem breus introduccions al trencament espontani de simetria (SSB) i al CCWZ, degut a la seva importància per entendre el SM i pel seu rol central en l’estudi de física més enllà del model estandard.
En el Capítol 2 estudiem les implicacions del descobriment del Higgs per diversos models de Higgs compost. Això ho fem utilitzant les senyals dels acoblaments mesurades pels experiments just després del seu descobriment al 2012, que ens permeten reduir de forma significativa el espai de paràmetres d’aquests models.
En el Capítol 3 ens centrem en l’estudi dels acoblaments del Higgs en models de Higgs compostos basats en el cose SO(5)/SO(4). En aquest apartat mostrem que els acoblaments del Higgs a gluons i fotons és poc sensible a resonàncies fermiòniques lleugeres si assumim que la simetria CP es conserva. També, trobem a primer ordre en els “mixings”, l’acoblament del Higgs a tops i gluons, i veiem que quan els normalitzem al Model Estàndard són iguals.
En el Capítol 4, estudiem la relació entre els acoblaments del Higgs i la seva massa en models Supersimetrics, i trobem que la massa del Higgs de 125 GeV i la senyal dels acoblaments mesurats poden ser competitius per excloure parts del espai de paràmetres del sector de Higgs. Nosaltres ens centrem en el MSSM amb stops pesats, i possibles extensions que disminueixen el “petit” problema de les jerarquies.
La segona part d’aquesta tesi va ser motivada per dos papers que van fer Rychkov et al. on presenten un nou mètode prometedor per poder solucionar sistemes fortament acoblats. El mètode consisteix en millorar el ja conegut Mètode de Truncació Hamiltoniana que s’utilitza per resoldre numericament sistemes fortament acoblats. La millora ve de integrar analiticament els modes més energètics de la teoria, cosa que fa millorar de forma substancial el resultat numèric, i permet reduir la demanda computacional per poder resoldre el sistema. Aquesta feina la presentem en el Capítol 5, on millorem el mètode a partir de trobar les expressions generals que són necessàries per dur a terme el procediment d’integrar els modes més energètics; a la vegada també resolem algunes de les qüestions que s’havien plantejat en articles anteriors a la nostra feina.This thesis is based on the publications done as a PhD student at IFAE during the periods 2012-2013 and 2015. These include two separate topics, Higgs phenomenology at the LHC within the frameworks of Composite Higgs and Supersymmetry and the improvement of the Renormalized Hamiltonian Truncation Method (RHTM). The first part of this thesis was motivated by the Naturalness problem in the Standard Model (SM), which was triggered by the discovery in 2012 of a scalar particle with a mass of 125 GeV and signal strengths compatible with the SM Higgs. The aim of these projects was to asses the impact of the measured mass and signal strengths on two of the best motivated frameworks that tackle the Naturalness problem; Composite Higgs and Supersymmetric extensions of the SM. This part of the thesis is organised as follows. In Chapter 1 we give an overview to the SM its shortcomings and motivate the need to go beyond the Standard Model (BSM). Brief introductions to Spontaneous Symmetry Breaking (SSB) and the CCWZ are also included due to their importance in the understanding of the SM and their pivotal role in the study of BSM physics . In Chapter 2 we study the implications of the Higgs discovery for different Composite Higgs models. This is done by using the signal strengths given by the experiments right after the Higgs discovery in 2012, which allow to greatly constrain the parameter space of some of these models. Chapter 3 is focused on the study of the Higgs couplings in Composite Higgs models based on the SO(5)/SO(4) coset. We show that the Higgs couplings to gluons and photons are insensitive to light fermionic resonances assuming that they preserve CP. Also, we find that at leading order in the mixings, the Higgs couplings to tops and gluons, when normalized to the Standard Model (SM), are equal. In Chapter 4 we study the relation between the Higgs couplings and the Higgs mass in Supersymmetric models while finding that the measured 125 GeV Higgs and the signal strengths can be competitive with direct searches in excluding some parts of the parameter space in the Higgs sector. We focus on the MSSM with heavy stops, and possible extensions that alleviate the small hierarchy problem. The second part of this thesis was motivated by two papers by Rychkov et al. where they present a promising new method to solve strongly coupled systems. The method consist in improving the already known Hamiltonian Truncation Method used to numerically solve strongly coupled systems. The improvement comes from analytically integrating out the high energy modes which results in a considerable improvement to the numerical result, and allows to reduce computational power needed to solve any given system. Our work, presented in Ch. 5, improves the method by finding the general expressions needed in the procedure to integrating out the high energy modes, and solves some of the issues left open in their work.
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Correia, Fagner Cintra [UNESP]. "Física de sabores e modelos multi-Higgs." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/108884.
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000775145.pdf: 580383 bytes, checksum: 157a2bbc4fd19cf65a3520aec3276fd9 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O modelo331 mínimo consiste em uma extensão ao Modelo Padrão amparada em SU'(3) IND.L' ? U'(1) IND. X'. Os férmions se transformam como tripletos ou anti-tripletos de SU'(3) IND. L' com componentes envolvendo quarks exóticos e partículas conhecidas da fenomenologia atual. Nosso objetivo aqui é explorar qualidades adicionais e limitar novos parâmetros do 331 a partir de processos que violem sabor, como a mistura de mésons neutros
The minimal 331 model has been proposed as an extension of the Standard Model based on the gauge group SU'(3) IND. L' ?U'(1) IND.X'. In this model, the left-handed fermions transform as triplets (or anti-triplets) under the action ofSU'(3) IND. L', whose generations correspond to the known SM fermions and new heavy quarks. Our purpose here is to constrain the 331 parameters considering the limits of ?avour changing processes as meson mixing
FAPESP: 11/16636-6
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Seymour, Michael H. "Predictions for Higgs and electroweak Boson production." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260459.
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Gothen, Peter Beier. "The topology of Higgs bundle moduli spaces." Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308587.
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Grant, Jackie. "Sphalerons in two Higgs doublet electroweak models." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341066.
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Cabi, Serkan. "Cosmology of hidden sector with Higgs portal." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52778.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 67-75).
In this thesis, we are investigating cosmological implications of hidden sector models which involve scalar fields that do not interact with the Standard Model gauge interactions, but couple directly to the Higgs field. We particularly focus on their relic particle density as a candidate for dark matter. For the case of hidden sector without a gauge field we have improved the accuracy of the bounds on the coupling constant and give bounds on the Lagrangian parameters. Models with Abelian and non-Abelian gauge fields are also studied with relic density bounds, BBN and galactic dynamics constraints. Several discussions on phase transitions and alternative dark matter candidates are included.
by Serkan Cabi.
Ph.D.
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Kling, Felix, Jose Miguel No, and Shufang Su. "Anatomy of exotic Higgs decays in 2HDM." SPRINGER, 2016. http://hdl.handle.net/10150/622345.
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Large mass splittings between new scalars in two-Higgs-doublet models (2HDM) open a key avenue to search for these new states via exotic heavy Higgs decays. We discuss in detail the different search channels for these new scalars at the LHC in the presence of a sizable mass splitting, i.e. a hierarchical 2HDM scenario, taking into account the theoretical and experimental constraints. We provide benchmark planes to exploit the complementarity among these searches, analyzing their potential to probe the hierarchical 2HDM parameter space during LHC Run 2.