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Dissertations / Theses on the topic 'Two Higgs Model'
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1
Sundu, Hayriye. "Lepton Flavor Violation In The Two Higgs Doublet Model." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608359/index.pdf.
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The lepton flavor violating interactions are interesting in the sense that they are sensitive the physics beyond the standard model and they ensure considerable information about the restrictions of the free parameters, with the help of the possible accurate measurements. In this work, we investigate the lepton flavor
violating H+ ! W+l and the lepton flavor conserving H+ ! W+l decays in the general two Higgs doublet model and we estimate decay widths of these decays. After that, we analyze lepton
flavor violating decay !
i in the same model and calculate its branching ratio. We observe that the
experimental results of the processes under consideration can give comprehensive
information about the physics beyond the standard model and the existing free
parameters.
2
Brawn, Gary Derrick. "Symmetries and topological defects of the two Higgs doublet model." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/symmetries-and-topological-defects-of-the-two-higgs-doublet-model(a8cafde7-383a-4190-a30e-0ba89d1178de).html.
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The standard model of particle physics is the most precisely verified scientific theory in the history of mankind. However, extended theories are already in place, ready to supersede the standard model should it fail to describe any new physics that may be observed in the next generation of high energy particle accelerators. One such minimal extension is the Two Higgs Doublet Model (2HDM). However, the appearance of additional symmetries to those of the gauge symmetries in the 2HDM can have consequences for the cosmological viability of the model, with the possibility for non-trivial topological defects forming during spontaneous symmetry breaking phase transitions.In this research we perform a systematic study of six accidental Higgs Family and CP symmetries that can occur in the 2HDM potential, by introducing and utilizing our Majorana scalar-field formalism. General sufficient conditions for convexity and stability of the scalar potential are derived and analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for each of the six symmetries are presented, in terms of the parameters of the theory. We identify the topological defects associated with the spontaneous symmetry breaking of each symmetry by means of a homotopy-group analysis. We find the existence of domain walls from the breaking of Z2, CP1 and CP2 discrete symmetries, vortices in models with broken U(1)PQ and CP3 symmetries and a global monopole in the SO(3)HF-broken model. We study the associated topological defect solutions as functions of the potential parameters via gradient flow methods. We also consider the cosmological implications of the topological defects and are able to derive bounds on physical observables of the theory in order to avoid contradictions with the theoretical limits on topological defects. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)Y hypercharge symmetry is discussed. In particular, the formalism may be used to properly identify seven previously hidden symmetries that may be manifest in a U(1)Y invariant scalar potential for particular choices of the model parameters.
3
Herquet, Michel. "A two-Higgs-doublet model : from twisted theory to LHC phenomenology." Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08212008-163854/.
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At the dawn of the Large Hadron Collider era, the Brout-Englert-Higgs mechanism remains the most appealing theoretical explanation of the electroweak symmetry breaking, despite the fact that the associated fundamental scalar boson has escaped any direct detection attempt. In this thesis, we consider a particular extension of the minimal Brout-Englert-Higgs scalar sector implemented in the Standard Model of strong and electroweak interactions. This extension, which is a specific, "twisted", realisation of the generic two-Higgs-doublet model, is motivated by a relative phase in the definition of the phenomenologically successful CP and custodial symmetries. Considering extensively various theoretical, indirect and direct constraints, this model appears as a viable alternative to more conventional scenarios like supersymmetric models, and gives grounds to largely unexplored possibilities of exotic scalar signatures at present and future collider experiments.
4
O'Neil, Deva A. "Phenomenology of the basis-independent CP-violating two-Higgs doublet model /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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5
Hasan, Nujmuddin. "Matter genesis in the extended standard model." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385473.
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6
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.
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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.
7
Altenkamp, Lukas [Verfasser], and Stefan [Akademischer Betreuer] Dittmaier. "Precise predictions within the Two-Higgs-Doublet Model / Lukas Altenkamp ; Betreuer: Stefan Dittmaier." Freiburg : Albert-Ludwigs-Universität Freiburg, 2017. http://d-nb.info/1126921424/34.
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8
Zhang, Huanian, and Huanian Zhang. "Direct and Indirect Searches for New Physics beyond Standard Model." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621580.
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The search for new physics beyond the Standard Model can follow one of two tracks: direct searches for new particles at the collider or indirect probes for new physics from precision measurements. In the direct searches for third generation squarks in SUSY at the LHC, the common practice has been to assume a 100% decay branching fraction for a given search channel. In realistic MSSM scenarios, there is often more than one signicant decay mode present, which signicantly weakens the current search limits on third generation squarks at the LHC. On the other hand, the combination of multiple decay modes as well as the new open decay modes offer alternative discovery channels for third generation squarks searches. In this work, we present the third generation squarks decay and the collider signatures in a few representative mass parameter scenarios. We then analyze the reach of the stop/sbottom signal for the pair production in QCD at the 14 TeV LHC with 300 fb⁻¹ integrated luminosity and of the 100 TeV future collider with 3000 fb⁻¹ integrated luminosity in a few representative scenarios. In the scenario of Bino LSP with Wino NLSP, we investigate stop/sbottom pair production at the LHC with one stop/sbottom decaying via t̃ --> t𝑥[0 1], t𝑥[0 2]/b̃ --> b𝑥[0 1], b𝑥[0 2], and the other one decaying via t̃ --> b𝑥[± 1]/b̃ -->t𝑥[± 1]. With the gaugino subsequent decaying to gauge bosons or a Higgs boson 𝑥[0 2] --> 𝑍𝑥[0 1], h𝑥[0 1] and 𝑥[± 1]--> 𝑊±𝑥[0 1], leading to 𝑏𝑏𝑏𝑏𝑗𝑗𝓁 Ɇᴛ final states for the Higgs channel and 𝑏𝑏𝑗𝑗𝑗𝑗𝓁𝓁Ɇᴛ final states for the 𝑍 channel, we study the reach of those signals at the 14 TeV LHC with 300 fb⁻¹ integrated luminosity. Because the sbottom and stop signals in the same SUSY parameter scenario have indistinguishable final states, they are combined to obtain optimal sensitivity, which is about 150 GeV better than the individual reaches of the sbottom or stop. In the scenario of Bino LSP with Higgsino NLSP. The light stop pair production at the 14 TeV LHC, with stops decaying via t̃₁ --> t𝑥[0 2]/𝑥[0 3] and the neutralino subsequently decaying to a gauge boson or a Higgs boson 𝑥[0 2]/𝑥[0 3] --> 𝑥[0 1]h/𝑍, leads to tt̄hh Ɇᴛ, tt̄h𝑍 Ɇᴛ or tt̄𝑍𝑍 Ɇᴛ final states. The above decay channels give rise to final states containing one or more leptons, therefore our search strategy is to divide the signal regions based on the multiplicity of leptons. We find that the one lepton signal region of channel tt̄h𝑍 Ɇᴛ has the best reach sensitivity of light stop searches at the 14 TeV LHC with 300 fb⁻¹ integrated luminosity. We then combine all the signal regions for a given decay channel or combine all the decay channels for a given signal region to maximize the reach sensitivity of the stop search. For the light stop pair production at the √s = 100 TeV future machine with 3000 fb⁻¹ integrated luminosity, we find that a stop with a mass up to 6 TeV can be discovered at 5𝜎 signicance, while a mass up to 6.8 TeV can be excluded at 95% C.L. for the combined results of all three channels. In the indirect probes for new physics, we utilize the 𝑍-pole Oblique Parameters 𝑆,𝑇, 𝑈 and Higgs precision measurements complementarily in the framework of the Two Higgs Doublet Model at current and future colliders. The 𝑆, 𝑇 , 𝑈 is not that sensitive to the rotation angle 𝛽-𝛼, while the Higgs precision measurements set strong constrains on 𝛽-𝛼. Also the 𝑇 is very sensitive to the mass difference of Higgs bosons, leading to the mass of charged Higgs (H±) aligning either along with the mass of neutral Higgs 𝐻 or 𝐴. As for the Higgs precision measurements, we consider the tree level corrections to Higgs coupling constants as well as the radiative corrections to Higgs coupling constants at one loop level for the future collider. The combination of 𝑍-pole precision measurements and Higgs precision measurements complementarily set strong constraints on the parameter space of the 2HDM, especially in the future 𝑒⁺𝑒⁻ circular collider compared to the current collider due to much cleaner backgrounds and higher luminosity.
9
Turan, Ismail. "Flavor Changing Neutral Current Processes In The Framework Of The Two Higgs Doublet Model." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/717843/index.pdf.
Full textAbstract:
It is widely believed that the Standard Model (SM) can not be a fundamental
theory of the basic interactions. Originated from this fact, many new physics
models have been proposed. Among them, the two Higgs doublet model (2HDM),
the SM enlarged by adding one extra scalar doublet, is considered as the simplest extension of the SM.
In this work, within the framework of the model III version of the 2HDM,
the exclusive decay the branching ratio is calculated and discussed in various physical regions determined by model parameters. It is
observed that it is possible to reach present experimental upper limits in model Finally, the
avor changing top quark decay,
10
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.
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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.
11
Bélusca, Hermès. "Recherche de nouvelle physique au LHC à partir d'une théorie des champs effective pour le boson de Higgs." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS032/document.
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La découverte au LHC d'un boson scalaire possédant des propriétés fortement similaires à celles du boson de Higgs du Modèle Standard, indique certainement que l'acteur principal du mécanisme de la brisure de symétrie électrofaible a été trouvé. Cependant, plusieurs théories au-delà du Modèle Standard prédisent l'existence d'une particule similaire provenant d'un secteur plus riche. La mesure des propriétés du boson scalaire découvert nous permettra de savoir si celui-ci correspond ou non à la particule prédite par le Modèle Standard. Pour ce faire, nous utilisons une approche modèle-indépendante via le cadre d'une théorie des champs effective (TCE) pour le boson de Higgs, afin de paramétrer les déviations de ses couplages à la matière par rapport au Modèle Standard. Nous nous focalisons sur une théorie basée sur un Lagrangien effectif de dimension 6, qui inclut à la fois des opérateurs de Charge-Parité paire et impaire. Dans un premier temps nous tentons d'obtenir des contraintes sur une partie des coefficients effectifs de Wilson, pertinents pour la physique du boson de Higgs au LHC, en utilisant les dernières données de taux du Higgs provenant du Run-I des expériences ATLAS et CMS, ainsi que des données de précision électrofaibles du LEP, SLC et du Tevatron. Nous montrons que les données actuelles sont capables de contraindre de manière significative les opérateurs de CP paire ainsi que certains opérateurs de CP impaire du Lagrangien effectif. Dans un second temps nous étudions de possibles désintégrations exotiques du boson de Higgs, qui ne sont générées qu'en tant que conséquence des opérateurs effectifs de dimension 6 (générés par de la nouvelle physique inconnue) et non par le Modèle Standard seul. Les limites expérimentales actuelles nous permettent de placer des bornes supérieures sur ces opérateurs. Pour finir nous analysons certaines limitations de l'approche effective, par la comparaison de certains processus avec boson de Higgs à l'ordre des arbres dans la TCE, avec les prédictions pour les mêmes processus calculés à l'arbre et à une boucle, dans une classe simple d'extensions du Modèle Standard connue sous le nom de "Two-Higgs doublet models"The discovery at the LHC of a scalar boson, the properties of which are strongly similar to the ones of the Standard Model Higgs boson, certainly indicate that the main actor of the electroweak symmetry breaking mechanism was found. However, many beyond-the-Standard Model theories predict the existence of such a similar particle coming from a richer sector. Measuring the properties of the discovered scalar will tell us whether or not it is the same particle as the one predicted by the Standard Model. To this aim we use a model-independent approach through a Higgs Effective Field Theory (EFT) framework to parametrize the deviations of its couplings to matter from the Standard Model. We focus on a Higgs EFT framework based on a dimension-6 effective Lagrangian, including both CP-even and CP-odd operators. We first attempt at putting constraints on a part of the effective Wilson coefficients relevant for Higgs physics at the LHC, using the latest Higgs rates data from the Run-I of the ATLAS and CMS experiments, as well as electroweak precision data from LEP, SLC and Tevatron. We show that the current data is able to significantly constrain CP-even and some CP-odd operators of the effective Lagrangian. We then move on to the study of possible exotic Higgs decays, that can only be generated as a consequence of the effective dimension-6 operators (generated from unknown new physics) and not from within the Standard Model alone, and derive upper bounds on those operators given the present experimental limits. Finally we analyze some of the limitations of the effective approach by comparing predictions on some Higgs processes at tree-level in EFT with respect to predictions at tree and 1-loop level on the same processes computed in a simple class of Standard Model extensions known as "Two-Higgs doublet models"
12
Acar, Hilal. "The Inclusive Semileptonic Decays Of The B-meson In A Cp Softly Broken Two Higgs Doublet Model." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604766/index.pdf.
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In this work, the B->X_dell ell decays are examined in the context of a CP softly broken two Higgs doublet model. The differential branching ratio, forward-backward asymmetry, CP-violating asymmetry, CP-violating asymmetry in the forward-backward asymmetry and polarization asymmetries of the final lepton in this decay are studied. The dependencies of these physical parameters on the model parameters are analyzed by paying a special attention to the effects of neutral Higgs boson (NHB) exchanges and possible CP violating effects. It has been found that NHB effects are quite significant for the tau mode and the above-mentioned observables seems to be promising as a testing ground for new physics beyond the SM, especially for the existence of the CP-violating phase in the theory.
13
Wiegand, Peter Christoph [Verfasser], and U. [Akademischer Betreuer] Nierste. "Parametrically enhanced two-loop contributions to $b\to s \gamma$ in a Two-Higgs-Doublet Model / Peter Christoph Wiegand ; Betreuer: U. Nierste." Karlsruhe : KIT-Bibliothek, 2017. http://d-nb.info/1144367697/34.
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Galler, Peter. "Effects of heavy Higgs bosons in the hadronic production of top-quark pairs including QCD corrections." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18796.
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In dieser Disseratation wird eine mögliche Erweiterung des Standardmodells der
Elementarteilchen (SM) im Higgs-Sektor mithilfe von Topquarkpaarproduktion am
Large Hadron Collider untersucht. Insbesondere wird dabei auf das sogenannte
Zwei-Higgs-Duplettmodell eingegangen. Dieses Modell führt mehrere Spin-0
Bosonen (auch Higgsbosonen genannt) zusätzlich zum SM-Higgsboson ein. Dabei
wird in dieser Arbeit von der Annahme ausgegangen, dass diese zusätzlichen
Higgsbosonen schwer genug sind um in ein Top-Antitop-Paar zu zerfallen. Somit
können die experimentellen Signaturen dieser neuen Teilchen mit Hilfe von
Observablen der Topquarkpaarproduktion untersucht werden. Dazu wird die
resonante Erzeugung von schweren Higgsbosonen und deren Zerfall in
Topquarkpaare bis einschließlich Quantenkorrekturen in der nächst-zu-führenden
Ordnung (NLO) in der QCD-Kopplungskonstanten berechnet. Weiterhin wird die
volle Spininformation des Top-Antitop-Paares beibehalten, welche die Analyse
von spinabhängigen Observablen erlaubt. Diese können, insbesondere in Falle von
Top-Antitop-Spinkorrelationen, sehr sensitiv auf Effekte schwerer Higgsbosonen
sein. Dies zeigt sich besonders in Vergleich zu spinunabhängigen Observablen.
Die Sensitivität von spinabhängigen Observablen kann zudem noch durch
entsprechende Schnitte auf den Phasenraum von Top- und Antitopquark verstärkt
werden. In dieser Dissertation wird ein Verfahren vorgestellt, mit dessen Hilfe
sich die Spinkorrelationen identifizieren lassen, welche die größte
Sensitivität auf die Effekte schwerer Higgsbosonen aufweisen. Außerdem wird
durch die Berechnung der Beiträge zur NLO u.a. gezeigt, dass diese Beiträge
wichtig sind um aussagekräftige und robuste Observablen zu definieren. Die
Ergebnisse der NLO, die in dieser Arbeit vorgestellt werden, sind die ersten
ihrer Art für die resonante Erzeugung von schweren Higgsbosonen und deren
Zerfall in Topquarkpaare.In this dissertation a possible extension of the standard model of particle physics (SM) in the Higgs sector is investigated using top-quark pair production at the Large Hadron Collider as a probe. In particular, the so-called two-Higgs-doublet model (2HDM) is studied. The 2HDM introduces several spin-0 bosons (which are also called Higgs bosons) in addition to the SM Higgs boson. In this thesis these additional Higgs bosons are assumed to be heavy enough to decay into a top-antitop quark pair. Thus, the experimental signatures of these new particles can be studied through observables of top-quark pair production. To this end the resonant production of heavy neutral Higgs bosons and their decay into top-quark pairs in calculated up to next-to-leading order corrections in the QCD coupling constant retaining the full spin information of the top-antitop pair. This allows to analyse spin dependent observables which can be more sensitive to effects of heavy Higgs bosons than spin independent ones especially in the case of top-antitop spin correlations. The additional application of kinematical cuts on the phase space of top and antitop quarks can enhance the sensitivity further. In this thesis a method is presented that can be used to construct the spin correlation which is most sensitive to the effects of heavy Higgs bosons on top-quark pair production. Furthermore, it is shown that the next-to-leading order corrections are required to construct observables which entail robust predictions. The results for the next-to-leading order in the QCD coupling constant presented in this thesis were the first ones given for resonant heavy Higgs production and decay into top-quark pairs.
15
Bernon, Jérémy. "Caractérisation du secteur de Higgs et aspects du problème de la saveur." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY020/document.
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Le Modèle Standard (MS) de la physique des particules s’est imposé comme étant la description la plus précise des interactions fondamentales entre les particules élémentaires. La découverte d’un boson de Higgs, avec une masse de 125 GeV, en Juillet 2012 au Large Hadron Collider (LHC), en a marqué sa confirmation définitive. Cependant, de nombreux problèmes observationnels et théoriques sont au coeur du MS, la plupart liés au secteur de Higgs. Etant une particule scalaire, le boson de Higgs souffre de très grandes corrections radiatives, ce qui déstabilise l’échelle électro-faible et mène au problème de hiérarchie. L’un des buts principaux du LHC est d’explorer précisément le secteur de Higgs, afin de caractériser le mécanisme à l’origine de la brisure de la symétrie électro- faible et de tester de possibles solutions au problème de hiérarchie. Le secteur de Higgs est également responsable de la génération des masses des fermions dans le MS, par le biais des couplages de Yukawa. Ces couplages sont extrêmement non génériques et cela mène aux problèmes de la saveur au delà du MS.La première partie de cette thèse se concentre sur la caractérisation précise du secteur de Higgs. En particulier, le code public Lilith est présenté, il permet de dériver des contraintes sur des scénarios de nouvelle physique à l’aide des mesures des propriétés du boson de Higgs en collisionneurs. Une analyse des couplages du boson de Higgs dans le contexte de plusieurs scénarios est ensuite effectuée. Dans la seconde partie, la phénoménologie des modèles à deux doublets de Higgs est étudiée à la lumière des résultats de la première phase du LHC. La limite d’alignement, ainsi que la possible présence de bosons de Higgs légers, sont étudiées en détail. Finalement, dans la dernière partie de cette thèse, l’hypothèse de Violation Minimale de la Saveur est introduite comme une solution potentielle aux problèmes de la saveur au delà du MS. Appliquée au Modèle Standard Supersymétrique Minimal, l’évolution des couplages baryoniques violant la parité R sous le groupe de renormalisation est analysée en détailThe Standard Model (SM) of particle physics stands as the most successful description of the fundamental interactions between elementary particles. The discovery of a Higgs boson, at a mass of 125 GeV, in July 2012 at the Large Hadron Collider (LHC), marked its ultimate confirmation. However, various observational and theoretical problems lie in the heart of the SM, with the majority of them linked to the Higgs sector. Being a scalar, the Higgs boson is subject to very large radiative corrections and this ultimately leads to the electroweak hierarchy problem. One of the main goals of the LHC program is to precisely probe the Higgs sector, in order to characterize the mechanism at the origin of the breaking of the electroweak symmetry and test possible solutions to the hierarchy problem. The Higgs sector is also responsible for the generation of the fermion masses, as it induces the Yukawa couplings. The SM flavor sector is highly hierarchical and this leads to flavor puzzles in theories beyond the SM.The first part of this thesis is dedicated to the precise characterization of the Higgs sector. In particular, the public tool Lilith is presented, which allows to derive constraints on new physics models based on the Higgs measurements at colliders. It is then used to perform global fits of the Higgs couplings in the context of various scenarios. In the second part, the phenomenology of two-Higgs-doublet models is studied in the light of the results from the first run of the LHC. The so-called alignment limit is explored in detail, as well as the possible presence of light scalar states. Finally, in the last part of this thesis, the Minimal Flavor Violation hypothesis is introduced as a possible solution to the flavor puzzles beyond the SM. Enforcing it in the Minimal Supersymmetric Standard Model, the renormalisation group evolution of the baryonic R-parity violating couplings is then studied in detail
16
Kucher, Inna. "Search for the Higgs boson decaying to two photons and produced in association with a pair of top quarks in the CMS experiment." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS181/document.
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Dans cette thèse, la mesure des propriétés du boson de Higgs dans le canal de désintégration en deux photons avec l'expérience CMS au Grand Collisionneur de Hadrons (LHC) est présentée. L'objectif de ce travail est l’étude du mode de production associé à une paire de quark top (tṫH). Ce mode représente le seul accès direct au couplage de Yukawa du quark top, un paramètre fondamental du Modèle Standard. Le mode de production tṫH est un processus très rare. Il est de l'ordre de deux ordres de grandeur plus petits que la production principale du boson de Higgs par fusion de gluons. À 13 TeV, le mode de production ttH est environ 4 fois plus grand qu'à 8 TeV. Cette thèse reprend les études réalisées à 8 TeV, où l’échantillon de données ne suffisait pas pour établir une observation de ce mode de production. Bien que le canal en deux photons ne soit pas celui qui présente le plus grand rapport de branchement (seulement 0,2%), il est très prometteur en raison de son excellente résolution en masse (1%). De plus, sa signature est très propre dans le détecteur. Le canal de désintégration en deux photons est particulièrement intéressant puisqu'il s'agit du seul canal permettant l'étude de tous les modes de production : la fusion de gluons, la fusion de bosons vecteurs, les productions associées avec des bosons W ou Z ou avec une paire de quarks top. Le document commence par une introduction théorique du Modèle Standard et la physique du boson de Higgs au LHC, suivie d'une description du détecteur CMS. Pour obtenir une excellente résolution de masse dans le canal de désintégration en deux photons , le calorimètre électromagnétique doit être calibré. Le système de monitorage de la transparence des cristaux du calorimètre électromagnétique de CMS par le système laser joue un rôle important dans la chaîne d'étalonnage et est décrit en détail. Sur le long terme, le système de monitorage laser devra être amélioré car le niveau de rayonnement influence son électronique. Je présente mon travail sur l'amélioration possible du système de monitorage laser, ainsi que l'étude de sa précision possible. L'analyse inclusive H → ᵞᵞ a eu plusieurs itérations pour les conférences en 2016 et 2017. La stratégie pour 2017 est décrite dans ce document. Une classification des événement sert à maximiser la significance du signal et à étudier les modes spécifiques de production du boson de Higgs. Mes contributions à l'analyse H → ᵞᵞ consistent en l'identification du vertex primaire, l'identification du photon et l'étude du mode de production tṫH. Chaque contribution est décrite en détail dans des chapitres dédiés. L'analyse tṫH, H → ᵞᵞ est présentée pour deux itérations en 2016 et 2017, en mettant l'accent sur les améliorations dans l'analyse de 2017. Enfin, les résultats de l'analyse inclusive et tṫH, H → ᵞᵞ, en utilisant l'ensemble complet de données 2016 correspondant à une luminosité intégrée de 35,9 fb-1, sont présentésIn this thesis, the measurement of the Higgs boson properties in the diphoton decay channel with the CMS experiment at the Large Hadron Collider (LHC) is presented. The focus of this work is the tṫH production mode, as it is the only direct access to the top quark Yukawa coupling, a fundamental parameter of the Standard Model. tṫH is a very rare process, two orders of magnitude smaller than the dominant Higgs boson production by gluon fusion. At 13 TeV, ttH production is about 4 times larger than at 8 TeV. This thesis takes over the studies performed at 8 TeV, where the statistics was not enough for an observation of ttH. Despite a very small branching ratio (only about 0.2%), the two photons decay channel of the Higgs boson is very promising, because of its excellent mass resolution (about 1%). Moreover, its signature in the detector is very clear. The diphoton decay channel is also of particular interest as it is the only channel allowing the study of all production modes: gluon fusion, vector boson fusion, associated productions with a W or a Z bosons, or with a top quark pair.The document starts with a theoretical introduction about the Standard Model and Higgs boson physics at LHC, followed by a description of the CMS detector. To achieve an excellent mass resolution in the H → ᵞᵞ channel, the electromagnetic calorimeter has to be calibrated. The laser monitoring system plays an important role in the calibration chain and it is described in details. On the long term, the laser monitoring system will have to be upgraded as level of radiation influences its electronics. I present my work on the possible upgrade of the laser monitoring system, along with the study of its possible precision.H → ᵞᵞ inclusive analysis had several iterations for conferences in 2016 and 2017. The strategy for 2017 is described in this document. An event classification is used to maximize the signal significance and to study specific Higgs boson production modes. My contributions to the H → ᵞᵞ analysis are primary vertex identification, photon identification and the study of the tṫH production mode. Each contribution is described in details in dedicated chapters. The tṫH, H → ᵞᵞ analysis is shown for two iterations in 2016 and 2017, with the emphasis on improvements in 2017 analysis. Finally, the results of the inclusive and tṫH, H → ᵞᵞ analysis, using the full 2016 dataset corresponding to an integrated luminosity of 35.9 fb-1, are shown
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Korutlu, Beste. "Lepton Flavor Violating Radion Decays In The Randall-sundrum Scenario." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609209/index.pdf.
Full textAbstract:
The lepton flavor violating interactions are worthwhile to examine since they
are sensitive to physics beyond the Standard Model. The simplest extension of
the Standard Model promoting the lepton flavor violating interactions are the
so called two Higgs doublet model which contains an additional Higgs doublet
carrying the same quantum numbers as the first one. In this model, the lepton
flavor violating interactions are induced by new scalar Higgs bosons, scalar h^0
and pseudo scalar A^0, and Yukawa couplings, appearing as free parameters, are
determined by using the experimental data. On the other hand, the possible
extra dimensions are interesting in the sense that they ensure a solution to the
hierarchy and cosmological constant problems and also result in the enhancement
in the physical quantities of various processes. In the present work, we predict
the branching ratios of lepton flavor violating radion decays r->e^+- mu^-+, r->
e^+- tau^-+ and r->
mu^+- tau^-+ in the two Higgs doublet model, including a single extra dimension, in the framework of the Randall Sundrum scenario. We observed that the branching ratios of the processes we study are at most at the order of 10^-8 for the small values of radion mass and it decreases with the increasing values of the radion mass. Among the LFV decays we study, the r->
mu^+- tau^-+ decay would be the most suitable one to measure its branching ratio.
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Paßehr, S. [Verfasser], Wolfgang F. L. [Akademischer Betreuer] Hollik, and Nora [Akademischer Betreuer] Brambilla. "Two-Loop Corrections to the Higgs-Boson Masses in the Minimal Supersymmetric Standard Model with CP-Violation / Sebastian Paßehr. Gutachter: Nora Brambilla ; Wolfgang F. L. Hollik. Betreuer: Wolfgang F. L. Hollik." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1059221942/34.
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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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Lebedev, Oleg. "Spontaneous CP-Violation in Two Higgs Doublet Supersymmetric Models." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30640.
Full textAbstract:
An alternative approach to the problem of CP-violation
is presented. It is based on the possibility of
spontaneous CP-breakdown in models with two Higgs doublets.
General features of the phenomenon such as stability of the
vacuum and the existence of a light axion are discussed.
We investigate the feasibility of spontaneously broken
CP in the minimal supersymmetric models - the MSSM and
NMSSM. The latter is shown to be experimentally viable.
The phenomenological implications of the model such as
CP-violating effects in the kaon systems and a nonzero
neutron electric dipole moment are studied.Ph. D.
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Carvalho, Dorsch Gláuber. "The electroweak phase transition in two-Higgs-doublet models and implications for LHC searches." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/60614/.
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Köhlmann, Simon [Verfasser]. "Search for Higgs bosons in Two-Higgs-Doublet models in the h/H → WW(*) → evµv channel with the ATLAS detector / Simon Köhlmann." Wuppertal : Universitätsbibliothek Wuppertal, 2014. http://d-nb.info/1053770375/34.
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Pyarelal, Adarsh, and Adarsh Pyarelal. "Hidden Higgses and Dark Matter at Current and Future Colliders." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624536.
Full textAbstract:
Despite its indisputable successes, the Standard Model of particle physics (SM) is widely considered to be an effective low-energy approximation to an underlying theory that describes physics at higher energy scales. While there are many candidates for such a theory, nearly all of them predict the existence of additional particles beyond those of the Standard Model. In this work, we present three analyses aimed at discovering new particles at current and future particle colliders.
The first two analyses are designed to probe extended scalar sectors, which often arise in theories beyond the Standard Model (BSM). The structure of these extended scalar sectors can be described by a physically well-motivated class of models, known collectively as Two- Higgs Doublet Models (2HDMs). The scalar mass spectrum of 2HDMs is comprised of two CP-even states h and H, a CP-odd state A, and a pair of charged states H± . Traditional searches for these states at particle colliders focus on finding them via their decays to SM particles. However, there are compelling scenarios in which these heavy scalars decay through exotic modes to non-SM final states. In certain regions of parameter space, these exotic modes can even dominate the conven- tional decay modes to SM final states, and thus provide a complementary avenue for discovering new Higgs bosons.
The first analysis presented aims to discover charged Higgs bosons H± via top decay at the LHC. We find that the exotic decay modes outperform the conventional decay modes for regions of parameter space with low values of the 2HDM parameter tan β.
The second analysis aims to systematically cover all the exotic decay scenarios that are consistent with theoretical and experimental con- straints, at both the 14 TeV LHC and a future 100 TeV hadron collider. We find that the preliminary results are promising - we are able to ex- clude a large swathe of 2HDM parameter space, up to scalar masses of 3.5 TeV, for a wide range of values of tan β, at a 100 TeV collider.
In addition to these two analyses, we also present a third, aimed at discovering pair produced higgsinos that decay to binos at a 100 TeV collider. Higgsinos and binos are new fermion states that arise in the Minimal Supersymmetric Standard Model (MSSM). This heavily- studied model is the minimal phenomenologically viable incorporation of supersymmetry - a symmetry that connects fermions and bosons - into the Standard Model. In the scenario we consider, the bino is the lightest supersymmetric partner, which makes it a good candidate for dark matter. Using razor variables and boosted decision trees, we are able to exclude Higgsinos up to 1.8 TeV for binos up to 1.3 TeV.
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Béjar, Latonda Santiago. "Flavor changing neutral decay effects in models with two Higgs boson doublets: Applications to LHC Physics." Doctoral thesis, Universitat Autònoma de Barcelona, 2006. http://hdl.handle.net/10803/3375.
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Hessenberger, Stephan [Verfasser], Wolfgang F. L. [Akademischer Betreuer] Hollik, Alejandro [Gutachter] Ibarra, and Wolfgang F. L. [Gutachter] Hollik. "Two-Loop Corrections to Electroweak Precision Observables in Two-Higgs-Doublet-Models / Stephan Hessenberger ; Gutachter: Alejandro Ibarra, Wolfgang F. L. Hollik ; Betreuer: Wolfgang F. L. Hollik." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1152006819/34.
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Vaheid, Halimeh. "Generation and Validation of di-Higgs events in the 4τ final state." Thesis, Uppsala universitet, Högenergifysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355744.
Full textAbstract:
The Higgs self-coupling has a vital role by giving a deeper understanding of the Higgs particle. Furthermore, the way it opens to physics beyond the SM, encourages us to do MC simulationstudies for varying λ_hhh . In this project, we investigate the effects of choosing different values for λ_hhh on the kinematics of all particles involved in the hh → τ τ τ τ decay channel and the resultsare compared with what we get from the SM prediction of λ_hhh .The data show that λ_hhh more close to the SM trilinear Higgs self-coupling results in generatingthe Higgs particles with the higher masses and higher momenta. On the other hand, for the moremassive Higgs bosons we have more energetic neutrinos in the final states which escape from thedetector without being detected.
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"A two-Higgs-doublet model : from twisted theory to LHC phenomenology." Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08212008-163854/.
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LIN, ZHI-LONG, and 林志隆. "The two higgs-doublet extension of standard model and S3 symmetry." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/43690672481545130214.
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Bristow, Kieran Matthew. "A search for a standard model higgs boson decaying to two T leptons in the lepton-hadron final state." Thesis, 2014. http://hdl.handle.net/10539/15604.
Full textAbstract:
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2014.This thesis presents multiple studies contributing to the research conducted at the ATLAS experiment at the CERN facility in Switzerland. The areas of contribution include the ATLAS physics validation developments and the Standard Model Higgs boson decaying to two tau leptons search e ort. A section outlining the use and maintenance of the ATLAS TauValidation package details contributions made towards the ATLAS physics validation program.
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Lin, Kuo-Yen, and 林郭彥. "The study on a variant two-Higgs doublet model with anew Abelian gauge symmetry." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/4usz96.
Full textAbstract:
碩士國立臺灣大學
物理學研究所
107
This research is inspiring by the paper published by V. Barger and H.S Lee in 2012. Their idea is based on the gauge group SU(3)C X SU(2)L X U(1)Y X U(1)B and add fourth generation fermions and a complex scalar boson to realize the process that one gauge boson Z′ decays into four charged leptons. In this paper, we try to establish a theoretical model to realize Four leptons resonance. Unfortunately, the standard model + fourth generation fermions is basically ruled out by current Higgs boson experimental data. Therefore, we adopt the idea from the paper by Dipankar Das et al and embed our model into the framework of type-II two Higgs doublet model (type-II 2HDM). In this paper, we consider experimental constraints from several flavour violating processes and dark matter direct detection and see if this model can explain muon g-2 anomaly and dark matter. We found even for small coupling constant, it can still give an adequate contribution to muon g-2. This model has enough free parameters which can be fine tuned to satisfy the constraints from other experiments. In dark matter part, we found dark matter direct detection is a strong constraint for new added gauge boson Z′. This makes the model testable in the future dark matter search.
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Yang, Yong. "Search for a Standard Model Higgs Boson Decaying to Two Photons in CMS at the LHC." Thesis, 2013. https://thesis.library.caltech.edu/7345/1/thesis.pdf.
Full textAbstract:
In part I of this thesis, I perform a search for the Standard Model Higgs boson decaying into two photons using 5.08 fb-1 of data collected by the Compact Muon Solenoid (CMS) detector in 2011 at a center-of-mass energy √(s)= 7 TeV.
The result of this search is interpreted as a local excess in the mass around 123 GeV/c2 with an significance of 3.3 standard deviation. This excess was later confirmed in the data in 2012, and was an important contribution to the CMS discovery paper published in 2012.
This search makes use of the excellent energy resolution of the CMS crystal electromagnetic calorimeter (ECAL). The energy intercalibration of approximately 76,000 crystals is crucial to improve the resolution performance. I describe in detail a novel intercalibration method using neutral π0(η) → γγ decays. This method was the first one in CMS to reach 0.5% calibration precision in the central part of ECAL with pseudorapidity less than 1. This calibration improved the Higgs to two photons search sensitivity by about 30%, compared to the precalibration performed before the installation of ECAL in CMS detector.
In part II of this thesis, I perform a search for an excited muon decaying into one muon and one photon using 36 pb-1 of data collected in 2010 at √(s)= 7 TeV. The result of this search indicates no evidence for excited muons. I report the first upper limits on single excited muon production cross section at this collision energy, and exclude a new region of the parameter space of compositeness scale and excited muon mass. Assume the compositness scale is the same as the excited muon mass, excited muons are excluded below 1090 GeV/c2 at the 95% confidence level, representing the most stringent limits, as of the date when the analysis was first published.
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Dhaliwal, Saminder K. "Search for Neutral Minimally Supersymmetric Standard Model Higgs Decaying to Two Hadronic Taus with the ATLAS Detector in pp collisions at 7 TeV Center of Mass Energy." Thesis, 2013. http://hdl.handle.net/1807/35175.
Full textAbstract:
This thesis presents the first search for a neutral Minimal Supersymmetric Standard
Model Higgs boson decaying to a pair of hadronic taus in proton-proton collisions with
a center-of-mass energy of √s = 7 TeV. Results are presented for an integrated lumi-
nosity of 1.056 fb−1 using data from the ATLAS detector at the Large Hadron Collider.
After signal selection, 245 events are observed. The number of events is consistent the
background estimate of 256 ± 26. An exclusion limit for the Higgs boson production is
derived as a function of (cross-section)×(branching ratio). This limit is presented as a
function of two parameters: mA and tanβ in the mmax scenario. A point in the (mA, h
tanβ) phase space is excluded if the signal hypothesis is rejected at the 95% confidence level.
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Chung, Yi-Lun, and 鍾沂倫. "Constraints on Two Higgs Doublet Models." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ksqbe8.
Full textAbstract:
碩士國立清華大學
物理學系
105
We studied the relation between the mass of charged scalar boson and vacuum expectation value ratio(tan β) in the four types 2HDM. According to the constraints on flavor physics B→Xsγ,B0−B0 mixing, Z→bb and Bs→µ+µ−, H± mass in the Type II and Flipped is larger than 500GeV. But there are no constraints on H± mass in the Type I and Lepton Specific when tanβ is larger than 2. On the contrary, in small tanβ region, H± mass becomes larger than 700GeV with the decreasing tanβ. Because mass is so heavy at low tanβ region, we choose that tanβ is larger than 1 in the next step, which is the analysis of the ATLAS Higgs physics data according to the ATLAS paper. Next, we can test new model via signal strength analysis. However, there are information of production and final state both in signal strength. If we want to look into different production µhZZ∗ cross sections, we can define the ratio R≡ VBF/ggh. It is independent to theoretical predictions on partial decay width and branch ratio. Moreover, many experimental systemic uncertainties can be cancelled in this ratio. We choose gg→H→WW∗ for our reference because it has smallest statistical and overall uncertainties. As results of this method, we find that the constraint on the Lepton Specific is better than using ordinary signal strength method.
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Mosomane, Chuene Johannes. "Two Higgs-doublet models in future e−p colliders." Thesis, 2018. https://hdl.handle.net/10539/26037.
Full textAbstract:
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in the School of Physics. Johannesburg, 2016.We review the general two Higgs doublet model and its particle spectrum. This model has four types, which are Type-I, Type-II, Type-X (lepton specific) and Type-Y (Flipped). We discuss the Madala hypothesis as a Type-II two Higgs doublet model, where the Madala hypothesis introduces the Madala boson (which is a doublet-like heavy Higgs boson) with mH = 270 GeV. We study the Madala boson in the proposed LHeC, which is a ep collider. The Madala boson has a higher crosssection in the LHeC with proton beam energy of Ep = 7 TeV in the charge current and the neutral current is suppressed.
LG2018
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Nackenhorst, Olaf. "Search for the Standard Model Higgs boson produced in association with tt and decaying into bb at 8 TeV with the ATLAS detector using the Matrix Element Method." Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0023-966A-8.
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Kubocz, Michael [Verfasser]. "Higgs production via gluon fusion in association with two or three jets in supersymmetric models / von Michael Kubocz." 2009. http://d-nb.info/100429302X/34.
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Manteuffel, Andreas von [Verfasser]. "Two aspects of high energy physics : methods for extended higgs models and constraints on the colour dipole picture / by Andreas von Manteuffel." 2008. http://d-nb.info/989951715/34.
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