Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Flavour changing.

Дисертації з теми "Flavour changing"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями

Оберіть тип джерела:

Ознайомтеся з топ-40 дисертацій для дослідження на тему "Flavour changing".

Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.

Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.

Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.

1

Smith, Daniel. "Study of the flavour changing neutral current β-s#gamma# at BaBar." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272066.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
2

Lin, Chi-Jen David. "Flavour changing neutral current processes of B and K mesons from lattice QCD." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/12420.

Повний текст джерела
Анотація:
Flavour Changing Neutral Current (FCNC) processes are essential for pinning down free parameters in the Standard Model and for probing possible new physics beyond it. In this work, we compute the non-perturbative strong-interaction effects on a collection of FCNC processes using Lattice QCD. Ratios of the relevant matrix elements of Kaon processes are computed for several initial and final meson momenta and for six light-meson masses ranging from approximately 435 MeV to 815 MeV. Fits of these ratios to the mass and recoil behaviours predicted by Chiral Perturbation Theory are then used to extract the relevant bag parameters.
Стилі APA, Harvard, Vancouver, ISO та ін.
3

Cotellucci, Alessandro. "Flavour constraints on sequestered supersymmetry breaking in string models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21709/.

Повний текст джерела
Анотація:
The Standard Model (SM) is the best theory which describes Nature at the fundamental level. Even if it provides very accurate predictions, the SM features some open problems. A promising extension of the SM is the Minimal Supersymmetric Standard Model (MSSM) provided by supersymmetry. The MSSM can provide solutions for some of the open problems of the SM but it can suffer from the flavour supersymmetric problem associated with the presence of large Flavour Changing Neutral Currents (FCNCs). The flavour supersymmetric problem is related to the mechanism which mediates supersymmetry breaking from the hidden to the visible MSSM sector. A popular supersymmetry breaking mediation mechanism is gravity mediation but generic gravity mediated models lead to large FCNCs. The conditions to avoid FCNCs in gravity mediated models are called mirror mediation. These conditions can naturally be satisfied in 4D string compactifications. 4D string models introduce new scalar particles, the moduli, which interact gravitationally with matter and represent natural candidates to mediate supersymmetry breaking to the MSSM. Promising 4D string scenarios are sequestered models where the MSSM lives on branes at singularities and the visible sector is sequestered from the sources of supersymmetry breaking in the bulk of the extra dimensions. So one can realise low-energy supersymmetry and all moduli can be heavy enough to avoid any cosmological moduli problem. In this thesis we shall focus on 4D sequestered string scenarios and determine which models can reproduce mirror mediation without the production of large FCNCs. We will find two different classes of sequestered models where only one can be compatible with present flavour constraints on FCNCs. This comparison with observations will provide information on important details of the microscopic theory like the functional dependence on the extra-dimensional volume of the physical Yukawa couplings and the Kähler potential for matter fields.
Стилі APA, Harvard, Vancouver, ISO та ін.
4

Kachanovich, Aliaksei [Verfasser], and U. [Akademischer Betreuer] Nierste. "Flavour-changing neutral current processes beyond the Standard Model / Aliaksei Kachanovich ; Betreuer: U. Nierste." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/123047577X/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
5

Kennedy, John James. "A search for single top-quark production and flavour-changing neutral-current interactions at H1." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269575.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
6

Wolff, Robert. "Searches for ttH and flavour-changing t –> Hq productions in multileptonic final states with the ATLAS detector." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0304/document.

Повний текст джерела
Анотація:
Cette thèse de doctorat décrit la recherche de la production du boson de Higgs associée à une paire de quarks tops (tt̅H) dans un ensemble de données de collisions proton-proton à une énergie de centre de masse de √s = 13 TeV et avec une luminosité intégrée de 36,1 fb⁻¹, enregistrée par le détecteur ATLAS en 2015 et 2016. Sept états finaux, correspondants à différentes désintégrations du boson de Higgs, sont optimisés pour une meilleure séparation du signal par rapport au bruit de fond. Un excès d’événements par rapport au bruit de fond MS est observé avec une signification de 4,1 écarts types, tandis que 2,8 sont attendus. En combinaison avec des résultats de recherches avec d’autres canaux de désintégration du boson de Higgs, la production de tt̅H a été découverte par le détecteur ATLAS en utilisant jusqu’à 79,8 fb⁻¹ de données de collisions à √s = 7, 8 et 13 TeV.Les courants neutres, qui changent de saveur dans la désintégration du quark top en un boson de Higgs et un quark léger (t → Hq), sont fortement supprimés dans le MS. Des nouveaux modèles physiques peuvent prédire un rapport d’embranchement de t → Hc de 0,15%. La recherche de ces désintégrations, avec un état final à deux ou trois leptons, n’observe aucun signal. Une limite supérieure sur le ratio d’embranchement de t → Hc (t → Hu) avec un niveau de confiance de 95% est observé à 0,16% (0,19%) avec une limite attendue de 0,15% (0,15%).Pour contourner la limitation du nombre insuffisant des collisions, le LHC et ses expériences prévoient un plan de mise à niveau ambitieux. Un système de démonstration est en service depuis 2015 et ses performances étudiées avec des données de calibrations et de collisions
This doctoral thesis describes the search for the associated Higgs boson production with a pair of top quarks (tt̅H) in a dataset of proton-proton collisions at a center-of-mass energy of √s = 13 TeV and with an integrated luminosity of 36.1 fb⁻¹, recorded by the ATLAS detector in 2015 and 2016. Seven final states, associated to different Higgs boson decay, are optimised to get the best signal to background separation. An excess of events over the SM background is observed with a significance of 4.1 standard deviations, while 2.8 are expected. In combination with search results obtained for other Higgs boson decay channels, the tt̅H production has been discovered with the ATLAS detector using up to 79.8 fb⁻¹ of collision data at √s = 7, 8 and 13 TeV.Flavour-changing neutral currents in top quark decays into a Higgs boson and a light up-type quark (t → Hq) are strongly suppressed in the SM. New physics models can predict a t → Hc decay branching ratio of 0.15%. The search for these decays in final states with two or three leptons observes no signal. An upper limit on the t → Hc (t → Hu) decay branching ratio at a 95% confidence level is set at 0.16% (0.19%) with an expected limit of 0.15% (0.15%).To bypass the limitation of an insufficient amount of collision data, the LHC and its experiments foresee an ambitious upgrade plan. The current ATLAS Liquid Argon Calorimeter readout will be replaced to get an increased granularity to improve the trigger selectivity and avoid bandwidth saturation at high luminosity. A demonstrator system has been operated since 2015 and its performance studied with calibration and collision data
Стилі APA, Harvard, Vancouver, ISO та ін.
7

Friedrich, Conrad. "Search for single top-quark production via flavour-changing neutral currents in strong interactions using s = 8 TeV ATLAS data." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2015. http://dx.doi.org/10.18452/17348.

Повний текст джерела
Анотація:
In dieser Dissertation werden Resultate einer Suche nach der Produktion von Einzel-Top-Quarks über flavour-verletzende neutrale Ströme (FCNCs) in starken Welchselwirkungen vorgestellt. Hierfür werden Daten aus Proton-Proton-Kollisionen am Large Hadron Collider bei einer Schwerpunktsenergie von 8TeV verwendet. Die Daten wurden mit dem ATLAS-Experiment im Jahr 2012 aufgenommen und entsprechen einer integrierten Luminosität von 14.1 fb−1. In der Analyse werden FCNC-Ereignisse selektiert, in denen ein leichtes Quark (u oder c) mit einem Gluon wechselwirkt, und ein einzelnes Top-Quark und potentiell ein weiterer einzelner Jet produziert wird. Mittels der Forderung nach genau einem Myon oder Elektron, großer fehlender Transversalenergie und exakt einem Bottom-Quark-Jet und eventuellem zusätzlichen Jet im Endzustand werden Kandidaten der gesuchten Ereignisse im leptonischen Zerfallskanal des Top-Quarks selektiert. Zur Unterscheidung zwischen Signal- und Untergrundereignissen werden multivariate Methoden herangezogen. Künstliche neuronale Netze werden verwendet, um diverse kinematische Variablen zu einem einzelnen Klassifikator zu kombinieren. Um die potentielle Produktion von Top-Quarks über FCNCs zu quantifizieren, werden die Ausgaben der neuronalen Netze einer Bayes''schen statistischen Analyse unterzogen. Da kein Überschuss an Signalereignissen festgestellt werden kann und die Ergebnisse den Erwartungen der theoretischen Vorhersagen entsprechen, werden neue obere Schranken auf den FCNC-Produktionswirkungsquerschnitt von Einzel-Top-Quarks ermittelt. Aus diesen werden unter Verwendung von modell-unabhängigen theoretischen Berechnungen neue obere Schranken auf die Kopplungskonstanten sowie auf die entsprechenden Verzweigungsverhältnisse ermittelt.
This thesis presents results of a search for single top-quark production via flavour-changing neutral currents (FCNCs) in strong interactions using data recorded with the ATLAS experiment at the Large Hadron Collider in 2012. A dataset from proton-proton collisions at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 14.1 fb−1 is used. It is searched for FCNC events in which a light quark (u or c) interacts with a gluon to produce a single top quark, either with or without the associated production of another light quark or gluon. Candidate events of leptonically decaying top-quarks are selected by requiring a single electron or muon, a substantial amount of missing transverse energy, and exactly one or two jets of which exactly one has to fulfil a b-tagging criterion. Multivariate techniques are employed in order to distinguish between signal- and background-like events by making use of artificial neural networks that combine multiple kinematic variables into a single classifier output. A Bayesian statistical analysis is performed on the classifier outputs in order to quantify potential signs of FCNC single top-quark production. No excess in signal events is observed and the results are in agreement with the theory predictions. Consequently a new upper limit is set on the FCNC single top-quark production cross-section multiplied by the t->Wb branching fraction. Using theory calculations within a model-independent effective theory framework, this limit is converted into upper limits on the coupling constants of the FCNC interactions as well as into respective upper limits on the branching fractions.
Стилі APA, Harvard, Vancouver, ISO та ін.
8

Alhroob, Muhammad [Verfasser]. "Search for Flavour Changing Neutral Currents in Single Top-Quark Production at √s = 7 TeV with the ATLAS Detector / Muhammad Alhroob." Bonn : Universitäts- und Landesbibliothek Bonn, 2013. http://d-nb.info/1044869984/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
9

Arslan, Ozan [Verfasser]. "Search for Flavour Changing Neutral Currents through Single Top-Quark Production at radix 8 TeV with the ATLAS Detector / Ozan Arslan." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/114974491X/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
10

Alpigiani, Cristiano. "Search for rare B decays into two muons with the ATLAS detector." Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8922.

Повний текст джерела
Анотація:
The impressive progress that elementary particle physics made in the second half of the last century led to the formulation of a comprehensive theory, known as the Standard Model (SM), which correctly describes all fundamental interactions in nature, except for the gravitational one. Indirect discoveries have always played an important role in high energy physics scenario and indirect research can be considered to all intents and purposes complementary to the direct one, since allows to test much higher energy scales than those the current colliders are able to reach. This is very important now that electroweak precision tests and measurements on Flavour Changing Neutral Currents (FCNC) processes put very stringent constraints on physics beyond the SM, requiring it to appear at scales O(10 TeV). On the other hand, New Physics (NP) is expected already at scales O(1 TeV) in order to offer a natural explanation to the smallness of the Higgs mass. This scale is also confirmed by recent constraints on thermal dark matter [1] which show how new physics should manifest not far above the electroweak scale. Rare B decays have always played a crucial role in shaping the flavour structure of the SM and particle physics in general. Since the first measurement of rare radiative B æ Kú“ decays by the CLEO Collaboration [2] this area of particle physics has received much experimental and theoretical attention. In particular, FCNC B decays, involving the b-quark transition b æ (s, d) + “ and b æ (s, d) + ¸+¸≠(¸ = e, μ, ·, ‹), provided crucial tests for the SM at the quantum level since they proceed through loop or box diagrams, and they are highly suppressed in the SM (also by helicity). Hence, these rare B decays are characterised by their high sensitivity to NP. The B0 s æ μ+μ≠ channel is the most direct example of the b æ s ¸¸ transitions. The SM predicted branching ratio [3] can be enhanced by coupling to non-SM heavy particles, such as those predicted by the Minimal Supersymmetric Standard Model (MSSM) and other extensions. Updated measurements on the B0 s æ μ+μ≠ branching ratio have been presented by ATLAS [4], LHCb [5] and CMS [6] collaborations. In this thesis I will report all the studies I performed within the rare B decays ATLAS group, measuring the branching ratio of the B0 s æ μ+μ≠ channel on data collected during LHC Run 1. The first chapter provides a general introduction to the SM, focusing in particular on the flavour sector and the possible new physics scenarios. Chapter 2 briefly introduces the LHC collider and the ATLAS detector, detailing the muon and trigger systems, fundamental for the rare B decays measurements. In chapters 3 and 4, I will summarise the work done, during my presence at CERN, on the ATLAS semiconductor strip detector, monitoring the Lorentz angle during Run 1 and measuring the backplane resistance of the silicon modules installed in the ATLAS cavern. In chapter 5, I will review the strategy adopted to measure the B0 s æ μ+μ≠ branching ratio, reporting all the studies I performed on the combinatorial background, and the results obtained on 4.9 fb≠1 of data collected in 2011. Chapters 6 and 7 detail respectively the additional studies I performed on the 2011 datasets and all the tests I made in preparation for the analysis on 20 fb≠1 of data collected in 2012. I will show the studies on the discriminating variables for the rejection of the background, the tests on the multivariate analysis and on the possible strategies for the invariant mass fit for the extraction of the signal yield. All these studies proved to be fundamental for the 2012 measurement detailed in chapter 8.
Стилі APA, Harvard, Vancouver, ISO та ін.
11

Mollet, Simon. "Exploration of 6-dimensional models with non trivial topology and their predictions for fermions masses and mixings, neutrino physics, flavour changing interactions and CP violation." Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/230863.

Повний текст джерела
Анотація:
In this thesis, we study several scenarios which go beyond the Standard Model of particle physics with the aim of gaining a better understanding for the multiplication of fermion families, their masses and mixings pattern and its relation to CP violation. The common feature of the models we envisaged (and the guiding principle of the thesis) is the introduction of extra space dimensions. In a first attempt to explain the fermion mass structure, we elaborate on a model with two extra-dimensions and a Nielsen- Olesen vortex background established on it. In this framework, three families in 4D can be seen as different modes of a single generation in 6D, while their extra-dimensional wavefunctions turn out highly constrained by the dynamics, which allows to determined the mass matrices with few parameters. Moreover, with a few additional hypotheses only, it is possible to simultaneously account for the striking differences between neutrinos and charged fermions. After a summary of the model, we illustrate this with the explicit formulation of a benchmark model which reproduces convincingly all the mass and mixing parameters of the Standard Model, taking advantage of new, more precise numerical solutions of the field equations, and including the recent measurements of the Standard Model scalar boson mass and of the neutrino heta_13 mixing angle (the latter has however been correctly predicted by the model before its first measurement). We then turn to the predictions which mainly concern the neutrino and gauge sectors. In the former, we remind the Majorana nature, and the natural tendency for inverted hierarchy pattern with an almost maximally suppressed neutrinoless double beta decay. On the other hand, we predict new (neutral) gauge bosons whose couplings to fermions are not flavour-diagonal but are however constrained (in their strength and their flavour structure) by the 6D anatomy of the theory. We compare their detectability in precision low energy processes and at colliders (especially at the LHC), and show that in the simplest geometries at least, the bounds from the former exclude interesting phenomenology for the latter. Nevertheless, we turn to more phenomenological effective Lagrangians with the same overall structure and in which we are able to lower the mass scale of the new bosons to a reachable energy, and thus analyse the possible signatures for LHC.In the last part of this work, we turn to the issue of CP violation and show how in certain 6D models with non simply connected topologies, it is possible to generate a non negligible CP violation at the 4D level in a pure gauge approach. We carefully study how the 4D CP symmetry is related to particular transformations of the original 6D theory and subsequently show how an incompatibility of such transformations with the compactification scheme can lead to an effective CP breaking. As a proof of concept, we build a toy model with two extra-dimensions compactified on a flat torus and end in 4D with a light neutral fermion with a non zero electric dipole moment.Dans cette thèse, nous étudions plusieurs scénarios au-delà du Modèle Standard de la physique des particules à la recherche d'une meilleure compréhension de la multiplication des familles de fermions, de leurs masses et de leurs mélanges, ainsi que la relation à laviolation de CP.La caractéristique commune à tous les modèles envisagés (et le concept sous-jacent à toute la thèse) est l'introduction de nouvelles dimensions spatiales. Dans une première tentative pour expliquer le spectre des fermions, nous développons un modèle où une structure de vortex à la Nielsen-Olesen est établie sur deux dimensions supplémentaires. Dans ce cadre, les trois familles à 4D peuvent être vues comme différents modes d'une unique génération à 6D, tandis que leur fonctions d'onde extra-dimensionnelles s'avèrent fortement contraintes par la dynamique ;ceci permet d'établir les matrices de masses en terme d'un petit nombre de paramètres. De plus, grâce à quelques hypothèses additionnelles seulement, il est possible de justifier simultanément les différences marquées entre neutrinos et fermions chargés. Nous synthétisons le modèle et l'illustrons en en formulant une réalisation particulière qui parvient à reproduire de manière convaincante tous les paramètres de masse et de mélange du Modèle Standard. Pour l'occasion, nous exploitons de nouvelles solutions aux équations des champs, numériquement plus précises, et prenons en compte les mesures récentes de la masse du boson scalaire et de l'angle de mélange heta_13 pour les neutrinos (le modèle avait cependant prédit ce dernier avant qu'il ne soit mesuré pour la première fois). Nous nous tournons ensuite vers les prédictions du modèle et qui concernent principalement le secteur des neutrinos et celui des bosons de jauge. Pour le premier, nous rappelons la nature "Majorana" des neutrinos, ainsi que la tendance naturelle à une hiérarchie inverse avec une suppression quasi maximale de la double désintégration bêta sans neutrino. D'autre part, nous prédisons de nouveaux bosons de jauge (neutres) dont les couplages aux fermions ne sont pas diagonaux dans l'espace des saveurs mais sont contraints (autant en terme de valeurs qu'en termes de structure) par l'anatomie de la théorie à 6D. Nous comparons leurs détections potentielles dans les processus de précision à basse énergie et auprès des collisionneurs (en particulier au LHC). Nous montrons que, dans les géométries les plus simples du moins, les limites imposées par les premiers excluent toute phénoménologie intéressante du côté des seconds. Toutefois, en nous tournantvers des Lagrangiens effectifs qui conservent la même structure d'ensemble mais ouvrent à une étude plus phénoménologique, nous sommes capables de réduire l'échelle de masse de ces nouveaux bosons jusqu'à une énergie accessible, et donc d'en analyser de potentielles signatures au LHC.Dans la dernière partie de ce travail, nous nous intéressons à la question de la violation de CP et montrons comment dans certains modèles à 6D avec une topologie non-simplement connexe, il est possible de générer une violation de CP non négligeable à 4D dans une approche de "pure jauge". Nous étudions attentivement comment la symétrie CP à 4D est reliée à des transformations particulières de la théorie originale à 6D, suite à quoi nous montrons comment l'incompatibilité de ces transformations avec la façon dont sont "compactifiées" les dimensions supplémentaires peut conduire à une brisure effective de CP. Pour illustrer la faisabilité de notre approche, nous élaborons un "modèle jouet" où deux dimensions supplémentaires sont compactifiées sur un tore plat, et obtenons à 4D un fermion neutre léger et qui possède un moment électrique dipolaire non nul.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Стилі APA, Harvard, Vancouver, ISO та ін.
12

Friedrich, Conrad [Verfasser], Ulrich [Akademischer Betreuer] Husemann, Heiko [Akademischer Betreuer] Lacker, and Arno [Akademischer Betreuer] Straessner. "Search for single top-quark production via flavour-changing neutral currents in strong interactions using s = 8 TeV ATLAS data / Conrad Friedrich. Gutachter: Ulrich Husemann ; Heiko Lacker ; Arno Straessner." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2015. http://d-nb.info/1078666466/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
13

Borsato, Martino. "Study of the BO to Kstar0 electron positron decay with the LHCb detector and development of a novel concept of PID detector : the Focusing DIRC." Sorbonne Paris Cité, 2015. https://theses.hal.science/tel-01456521.

Повний текст джерела
Анотація:
Les courants neutres changeant le saveur de type b —>sy sont interdites au niveau de l'arbre dans le Modèle Standard (MS) et ils se produisent au premier ordre à travers des diagrammes radiatives à boucle. Par conséquent, ils sont sensibles à la Nouvelle Physique (NP), qui peut contribuer soit au niveau de l'arbre ou de la boucle. En outre, la chiralité de l'interaction faible dans le MS implique que le photon émis a une polarisation gauche. Cependant, toute une classe de théories de NP ne partagent pas cette caractéristique du MS et pourraient se manifester sans ambiguïtés comme une contribution droite à la polarisation. Cette thèse présente la première étude de la polarisation du photon provenant du processus b —>sy à travers une analyse angulaire du canal BO —>K* 0 e+e-. Même si BO —> *K* 0 e+e- n'est pas une transition b—>s de type radiative, la contribution avec un photon virtuel qui se couple à la paire de leptons domine dans la région de bas q carré. De plus, le canal avec des électrons plutôt que des muons permet de mieux isoler cette contribution à l'extrémité inférieure du spectre de q carré. La luminosité intégrée de 3 fb-1 recueillie par LHCb au cours du Run 1 du LHC a permis pour la première fois de sélectionner un échantillon d'évènements B0—>K* 0 e+e¬ assez grands pour mesurer les asymétries transverses AT(2)=-0. 23±0. 23±0. 05 et ATIm=0. 14±0. 22±0. 05 dans la région de bas q carré entre 0. 002 GeV2/c4 et 1 GeV2/c4. Ces mesures sont consistent avec les prédictions du MS et ils fournissent de nouvelles contraintes sur les contributions droitiers à la polarisation avec le même niveau de précision que ceux venant des mesures faites avec des désintégrations radiatives. Les expériences de physique du saveur nécessitent de détecteurs avancés dédiés à l'identification des différentes saveurs des hadrons chargés. Ces détecteurs sont pour la plupart basés sur la détection de la lumière Cherenkov émise par ces particules lorsqu'elles traversent un milieu diélectrique. Cette thèse présente également l'activité de R&D sur un nouveau concept de détecteur basé sur le détecteur DIRC de l'expérience BABAR : le FDIRC. Son design est destiné à l'utilisation dans un environnement avec un bruit de fond deux ordres de grandeurs plus grand que dans BABAR grâce à une caméra d'imagerie plus rapide, de dimension réduite et composée de silice fondue résistant à l'irradiation. Le premier prototype à grande échelle a été testé au télescope à rayons cosmiques de SLAC et a démontré la faisabilité du concept de détecteur
Flavour-changing neutral current processes of the type b --+ sy are forbidden at the tree level in the Standard Model (SM) and occur at leading order through radiative loop diagrams. Therefore, they are sensitive to new physics (NP), which may contrebute either at the tree or loop level. Furthermore, the chirality of the weak interaction in the SM implies that the photon emitted has left-handed polarisation. However, a whole class of NP theories do not share this SM feature and may manifest unambiguously as a right-handed contribution to the polarisation. This thesis presents the first study of the b-* sy photon polarisation through an angular analysis of the B0-*K* 0 e+e- channel. Even though BO-*K* 0 e+e- is not a radiative b s transition, the contribution from a virtual photon coupling to the lepton pair dominates in the low-q2 region. Furthermore, the channel with electrons rather than muons allows to better isolate the virtual photon contribution at the low end of the q 2 spectrum. The integrated luminosity of 3 fb-1 collected by LHCb during LHC Run 1 allowed for the first time to select a sample of B0-›K* 0 e+e- events large enough to measure the transverse asymmetries AT(2)=-0. 23±0. 23±0. 05 and ATIm=0. 14±0. 22±0. 05 in the low q2 region between 0. 002 GeV2/c4 and 1 GeV2/c4. These measurements are found to be consistent with SM predictions and provide new constraints on right handed contributions to the photon polarisation at the same level of precision as the ones from measurements involving radiative decays. Flavour physics experiments require advanced detectors dedicated to the identification of the different flavours of charged hadrons. Most of them are based on the detection of the Cherenkov light emitted by these particles as they traverse a dielectric medium. This thesis presents also the R&D activity on a new detector concept based on the BABAR DIRC, the FDIRC. Its design is intended to operate the detector in an environment with background two orders of magnitude larger than BABAR thanks to a faster and smaller imaging camera made of radiation-hard fused silica. The first full-scale prototype of the FDIRC was tested at the SLAC Cosmic Ray Telescope and demonstrated the feasibility of the detector concept
Стилі APA, Harvard, Vancouver, ISO та ін.
14

Geßner, Gregor [Verfasser], Kevin [Akademischer Betreuer] Kröninger, and Wolfgang [Gutachter] Wagner. "Search for flavour-changing neutral currents in processes with a single top quark in association with a photon using a deep neural network at the ATLAS experiment at √s = 13TeV / Gregor Geßner ; Gutachter: Wolfgang Wagner ; Betreuer: Kevin Kröninger." Dortmund : Universitätsbibliothek Dortmund, 2019. http://d-nb.info/1203373015/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
15

Quintana, Boris. "Search for radiative B decays to orbitally excited mesons at LHCb." Thesis, Université Clermont Auvergne‎ (2017-2020), 2019. http://www.theses.fr/2019CLFAC060.

Повний текст джерела
Анотація:
Cette thèse présente une étude des désintégrations radiatives des mésons B0 et Bs, produits lors des collisions de protons du Grand Collisionneur de Hadrons (LHC), au Laboratoire Européen de Physique des Particules (CERN),vers des états orbitallement excités. Elle s’inscrit dans le contexte de recherche indirecte de physique au-delà du Modèle Standard de la Physique des Particules. Les données récoltées par le détecteur LHCb pendant le Run 1(2011-2012) et le Run 2 (2015-2018) du LHC, correspondant à une luminosité intégrée de 8.7 fb−1, sont utilisées pour l’analyse. Une sélection optimisée des états finals comprenant deux traces chargées et un photon est mise en place, permettant de regrouper un très grand échantillon de désintégrations radiatives de hadrons beaux. Un modèle est ajusté à la masse invariante du système, permettant de soustraire statistiquement les différentes contributions de bruit de fond polluant les données.Une première analyse en amplitude est ensuite mise en place pour une étude détaillée de la structure hadronique dans le mode Bs → K+K−γ. Elle permet la première observation du mode Bs → f2j (1525)γ avec une mesure de rapport d’embranchement normalisé à celui du mode dominant Bs → φγ:B(Bs → f2j γ) = (24.1 ± 0.9 (stat) +1.6 (syst) ± 0.6 (br)) × 10−2B(Bs → φγ)−0.8C’est également le second mode de désintégration radiative du méson Bs jamais observé. Une analyse similaire est faite pour le mode B0 → K±π∓γ, et permet une mesure préliminaire du rapport d’embranchement du mode B0 → K2∗(1430)γ, normalisé à celui du mode dominant B0 → K∗0γ:(B0 K∗0(1430)γ)B(B0 → K∗0(892)γ) = (36.4 ± 0.4 (stat) ± 1.3(BR))%Une étude détaillée des erreurs systématiques affectant la mesure reste néanmoins nécessaire pour connaitre sa compétitivité vis-à-vis des mesures actuelles. Utilisant une stratégie similaire, une sélection préliminaire des modes B K0hhγ est aussi mise en place pour estimer la statistique disponible à LHCb pour ces modes qui permettraient de mesurer la polarisation du photon dans la transition b sγ. Ce travail sera à la base d’une analyse portée sur les données du Run 3 du LHC
This document presents studies of radiative decays of B0 and Bs mesons to orbitally excited states, produced in proton collisions at the Large Hadron Collider (LHC) of CERN (European Council for Nuclear Research). It takes place in the context of the search for new physics processes beyond the standard model of particle physics. The work is based on the data collected at the LHCb experiment during the Run 1(2011-2012) and the Run 2 (2015-2018) of the LHC, which corresponds to an integrated luminosity of about 8.7 fb−1. First, an optimised selection of the final states comprising of two charged tracks and a high energy photon is put in place, regrouping a large samples of B hadron radiative decays. Then, a mass model is fit to the data distribution, allowing to statistically subtract the background contributions in the data set.A first amplitude analysis is then developed to study the hadronic structure in the Bs → K+K−γ decay mode. Resulting from this analysis is the first observation of the Bs → f2j (1525)γ mode together with a relative branching ratio measurement:B(Bs → f2j γ) = (24.1 ± 0.9 (stat) +1.6 (syst) ± 0.6 (br)) × 10−2B(Bs → φγ) −0.8It is the second radiative decay mode observed for the Bs meson. A similar analysis is performed on the B0 → K±π∓γ mode, allowing a preliminary measurement of the relative branching ratio of B0 → K2∗(1430)γ:(B0 K∗0(1430)γ)B(B0 → K∗0(892)γ) = (36.4 ± 0.4 (stat) ± 1.3(BR))%However, a detailed systematics study is needed to assess its competitivity with previous measurements of this decay mode. Making use of a similar selection strategy, a preliminary study of B K0hhγ modes is also set up during the thesis to estimate the available statistics for these modes at LHCb, which are particularly interesting to measure the photon polarisation in the b sγ transition. This work will be the starting point of an analysis comprising the future data that will be collected during the Run 3 of the LHC
Стилі APA, Harvard, Vancouver, ISO та ін.
16

Walston, Sean Eric. "Heavy flavor decays of the Z⁰ and a search for flavor changing neutral currents /." wwwlib.umi.com/cr/uoregon/fullcit?p3136452 view abstract or download file of text, 2004.

Знайти повний текст джерела
Анотація:
Thesis (Ph. D.)--University of Oregon, 2004.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 254-261). Also available for download via the World Wide Web; free to University of Oregon users.
Стилі APA, Harvard, Vancouver, ISO та ін.
17

Jäger, Sebastian. "Supersymmetric SO(10) unification and flavor changing weak decays." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969864647.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
18

Witchey, Nicholas James. "Search for flavor changing neutral current decays of charm mesons /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487935125882463.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
19

Poschenrieder, Anton. "The Littlest Higgs and its phenomenological implications for flavor changing neutral currents and lepton flavor violating processes." kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/626143/626143.pdf.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
20

Amanik, Philip. "Effects of non-standard neutrino flavor changing interactions in core collapse supernovae." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3216385.

Повний текст джерела
Анотація:
Thesis (Ph. D.)--University of California, San Diego, 2006.
Title from first page of PDF file (viewed September 5, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 87-89).
Стилі APA, Harvard, Vancouver, ISO та ін.
21

Kochebina, Olga. "Study of Rare Charm Decays with the LHCb Detector at CERN." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112208/document.

Повний текст джерела
Анотація:
Les désintégrations charmées rares interviennent principalement via des courants neutres changeant la saveur (FCNC). Le Modèle Standard (SM) n'autorise les courants qu'au niveau des boucles. Dans les désintégrations du charme, les FCNC sont sujets à une très efficace suppression de GIM. Des processus très rares sont donc à considérer. Ils sont d'excellents outils pour la recherche Nouvelle Physique (NP) au-delà du SM. Les particules de NP pourraient devenir détectables en écartant des observables telles que des rapports de branchement et des asymétries CP et angulaires prévisions de le SM. Le sujet principal de cette thèse est la mesure du rapport de branchement D0->K-π+ρ/ω(->µ+µ-). Il sera précieux en particulier en tant que mode de normalisation lors de l'étude de toutes les désintégrations D0 -> h-h’+ µ+µ- : D0 -> K-π+µ+µ-, D0 -> π+π-µ+µ-, D0 -> K+K-µ+µ- et D0 -> K+π-µ+µ-. En utilisant 2/fb de données collectées par LHCb en 2012, nous mesurons: B(D0 -> K-π+ ρ/ω (->µ+µ-)) = (4.37± 0.12(stat.) ±0.53(syst.)) ×10^-6. C'est la toute première mesure de ce mode. Nous avons également étudié la sensibilité qu'attendra LHCb dans les modes D0 -> h-h’+ µ+µ- pour la mesure de rapport des branchements totaux et partiels, et pour celle d'asymétries, avec les échantillons de données qui seront collectés d'ici 10 ans. Par ailleurs, nous avons déterminé les incertitudes systématiques touchant les recherches de désintégrations à trois corps, D+(s) -> π+µ+µ- et D+(s) -> π-µ+µ+, effectués par LHCb dans les données recueillies en 2011 (1/fb). Enfin, les tests effectués sue les prototypes des cartes d'électronique embarquée qui assureront la lecture des calorimètres de l'expérience le LHCb mise à jour sont présenté dans cette thèse
Rare charm decays proceed mostly through the c -> u Flavor Changing Neutral Current (FCNC), which is possible only at loop level in the Standard Model (SM). In charmed decays, FCNCs are subject to a very efficient GIM suppression, leading to very rare processes. Consequently, rare charm decays are good tools to probe to New Physics (NP) beyond the SM. NP particles could become detectable by causing observables such as branching ratios and CP or angular asymmetries to deviate from the SM predictions. The main subject of this thesis is the measurement of the branching ratio of the D0 -> K-π+ ρ/ω (->µ+µ-) mode. It will be precious in the future, in particular as a normalization mode in the study of all: D0 -> h-h’+ µ+µ- decays D0 -> K-π+µ+µ-, D0 -> π+π-µ+µ-, D0 -> K+K-µ+µ- and D0 -> K+π-µ+µ-. Using 2/fb of 2012 LHCb data we find: B(D0 -> K-π+ ρ/ω (->µ+µ-)) = (4.37± 0.12(stat.) ±0.53(syst.)) ×10^-6. This is the first measurement of this mode. We also determined sensitivities to total and partial branching fractions and asymmetries in D0 -> h-h’+ µ+µ- decays with future LHCb datasets. In addition, the systematic uncertainties affecting the searches for the 3-body decays, D+(s) -> π+µ+µ- and D+(s) -> π-µ+µ+, carried out by LHCb based on the data collected in 2011 (1/fb). Finally, the results of the tests of front-end electronic board for the Upgrade of LHCb are presented
Стилі APA, Harvard, Vancouver, ISO та ін.
22

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.

Повний текст джерела
Анотація:
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,
Стилі APA, Harvard, Vancouver, ISO та ін.
23

Shinohara, Satoshi. "Study of the KL→π⁰ννDecay at the J-PARC KOTO Experiment". Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/265175.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
24

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.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
25

Nicol, Michelle. "Analysis of the rare decay B->K*ee at LHCb." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112354/document.

Повний текст джерела
Анотація:
Grâce à la grande section efficace de production de paires bb, LHC offre une excellente occasion de faire des études de courants neutres changeant la saveur. Ces transitions sont sensibles aux effets de nouvelle physique. Cette thèse porte sur l'analyse des événements B->K*ee qui permettent de mesurer la fraction de photon avec une polarisation droite et donc de rechercher des signaux de nouvelle physique émis dans la transition b ->s. En effet, dans le Modèle Standard, la polarisation des photons est gauche. La paire e+e, lors que la masse invariante de la paire de leptons est basse, provient d'un photon virtuel et permet donc de sonder la polarisation de celui-ci. Cette mesure se fait grâce à l'étude des distribution angulaires de cette désintégration à quatre corps. Une première étape est la mesure du rapport d'embranchement dans le domaine de masse 30-1000MeV=c2. En effet, cette désintégration n'a jamais été observée dans cette région, y compris auprès des usines a B a cause du très faible rapport d'embranchement. Cette analyse comportant des électrons de basse impulsion transverse est expérimentalement complexe dans un environnement tel que celui du LHC. La mesure est faite relativement au rapport d'embranchement de la désintégration B->J/Psi(ee)K*. En effet, cela permet de s'affranchir de nombreux effets expérimentaux ainsi que de la détermination absolue des efficacités. Le résultat, repose sur les données collectées par LHCb en 2011 et correspondant a une luminosité intégrée de 1 fb-1: B(B->K*ee)30-1000MeV = (3:19+0:75-0:68(stat) +/- 0:21(syst) =/-0.15(PDG)) x10-7 en utilisant la valeur PDG pour le rapport d'embranchement de la désintégration B->J/Psi(ee)K*. La dernière partie de la thèse porte sur des études Monte Carlo qui montrent que la précision sur la fraction de photon avec une polarisation droite que l'on peut espérer obtenir avec l'inclusion des données de 2012 est d'environ 0.1, comparable à la moyenne mondiale obtenue avec des méthodes différentes
The high bb cross section produced by the LHC offers an excellent opportunity for thestudy of flavour changing neutral current B decays, where the effects of new physics can be probed. This thesis presents an analysis of the rare decay B->K*ee which can be used to measure the polarisation of the photon in the b -> s transition. When the dilepton mass is low, the ee pair comes predominantly from a virtual photon, and the polarisation can be accessed via an angular analysis. It is predicted to be predominantly left handed in the Standard Model, and therefore an enhanced right handed amplitude would be a sign of new physics. A first step is to measure the branching fraction in the dilepton mass range, 30 MeV to 1 GeV. This decay has not yet been observed in this region, due to its small branching ratio. The analysis involves electrons with low transverse momentum, and is thus experimentally complex in the hadronic environment at the LHC. The branching ratio is measured relative to that of B->J/Psi(ee)K*, which eliminates both certain experimental effects, and the need to determine absolute effciencies. The result is obtained with an integrated luminosity of 1 fb-1 of pp collisions, collected by LHCb during 2011 and is found to be:B(B->K*ee)30-1000MeV = (3:19+0:75-0:68(stat) +/- 0:21(syst) =/-0.15(PDG) x10-7 when using the PDG value for the B->J/Psi(ee)K* branching ratio. The last part of the thesis presents Monte Carlo studies, showing that with the inclusion of the 2012 data sample, the expected sensitivity on the fraction of right handed polarisation is approximately 0.1, which is comparable with the world average obtained with different methods
Стилі APA, Harvard, Vancouver, ISO та ін.
26

Sumensari, Olcyr. "Search of new physics through flavor physics observables." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS315/document.

Повний текст джерела
Анотація:
La recherche indirecte des effets de la physique au-delà du Modèle Standard à travers les processus de la saveur est complémentaire aux efforts au LHC pour observer directement la nouvelle physique. Dans cette thèse nous discutons plusieurs scénarios au-delà du Modèle Standard (a) en utilisant une approche basée sur les théories de champs effective et (b) en considérant des extensions explicites du Modèle Standard, à savoir les modèles à deux doublets de Higgs et les scénarios postulant l'existence des bosons leptoquarks scalaires à basse énergie. En particulier, nous discutons le phénomène de la brisure de l'universalité des couplages leptoniques dans les désintégrations basées sur les transitions b → sℓℓ et b → cτν, et la possibilité de chercher les signatures de la violation de la saveur leptonique à travers les modes de désintégration similaires. Une proposition pour tester la présence d'un boson pseudoscalaire léger à travers les désintégrations des quarkonia est aussi présentée
Indirect searches of physics beyond the Standard Model through flavor physics processes at low energies are complementary to the ongoing efforts at the LHC to observe the New Physic phenomena directly. In this thesis we discuss several scenarios of physics beyond the Standard Model by (a) reusing the effective field theory approach and (b) by considering explicit extensions of the Standard Model, namely the two-Higgs doublet models and the scenarios involving the low energy scalar leptoquark states. Particular emphasis is devoted to the issue of the lepton flavor universality violation in the exclusive decays based on b → sℓℓ and b → cτν, and to the possibility of searching for signs of lepton flavor violation through similar decay modes. A proposal for testing the presence of the light CP-odd Higgs through quarkonia decays is also made
Стилі APA, Harvard, Vancouver, ISO та ін.
27

Eygi, Zeynep Deniz. "The Standard Model Analyasis Of The Cp Violation In The Inclusive Semileptonic B-meson Decays." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12604712/index.pdf.

Повний текст джерела
Анотація:
Being a flavor changing neutral current process, inclusive semileptonic B- meson decays provide reliable testing grounds for the Standard Model at the loop level. They are also importanat in the CKM phenomology and investing the CP violation due to the existence of sizable interference terms in the decay amplitude. In this work , the rare inclusive semileptonic B- meson decays for (lepton is electron ,muon , tau) are investigated in the context of the Standard Model.The differential branching ratio, forward-backward asymmetry ,CP &ndash
violating asymmetry and CP &ndash
violating asymmetry in the forward-backward asymmetry in these processes are examined.The dependencies of these physical parameters on the Standard Model parametres are analyzed by paying a special attention to the long distance effects. Although the branching ratios predicted for the inclusive semileptonic B- meson decays are relatively small because of CKM suppression , it has been found that there is a significant ACP and ACP(AFB) for these processes.
Стилі APA, Harvard, Vancouver, ISO та ін.
28

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.

Повний текст джерела
Анотація:
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.
Стилі APA, Harvard, Vancouver, ISO та ін.
29

Yilmaz, Umit Oktay. "The Polarization Properties Of The Final State Particles In The Rare Radiative B-meson Decay." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606100/index.pdf.

Повний текст джерела
Анотація:
A general analysis of the photon and lepton polarizations in the rare Bs &
#8594
&
#61543
l+l- decay by using the most general model independent form of the effective Hamiltonian is presented. The total and the differential branching ratios for these decays, when photon is in the positive and negative helicity states, are studied. The sensitivity of "
photon polarization asymmetry"
and the longitudinal, transverse and normal polarization asymmetries of final state leptons, as well as lepton-antilepton combined asymmetries in Bs &
#8594
&
#61543
l+l- decay to the new Wilson coefficients are also investigated. It is shown that all these physical observables are very sensitive to the existence of new physics beyond SM and their experimental measurements can give valuable information about it.
Стилі APA, Harvard, Vancouver, ISO та ін.
30

Brost, Elizabeth. "Search for the Flavor-Changing Neutral Current in Top Pair Events in sqrt(s) = 8 TeV Proton-Proton Collisions at the Large Hadron Collider Using the ATLAS Detector." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20406.

Повний текст джерела
Анотація:
In this dissertation, a search for the flavor-changing neutral current in top-antitop events is presented. The flavor-changing neutral current is forbidden at tree level in the Standard Model and suppressed at higher order due to the GIM mechanism. In the Standard Model, the top quark is expected to decay to a W boson and a bottom quark nearly 100 percent of the time. While the Standard Model branching fractions for flavor-changing neutral currents in top decays are well beyond current experimental reach, there exist theoretical models which predict large enhancements to those branching fractions. Observation of the flavor-changing neutral current in top decays would be an unambiguous confirmation of new physics. This search was conducted in data from proton-proton collisions at the Large Hadron Collider, running at a center-of-mass energy of √s = 8 TeV, which were collected with the ATLAS detector in 2012. These data correspond to an integrated luminosity of 20.3 fb^-1. Candidate events include a lepton (electron or muon), a photon, at least two jets (one of which is b-tagged), and missing transverse energy. As no signal is observed, an observed (expected) upper limit on the branching ratio BR(t → qγ) of 0.063% (0.062%) is presented.
Стилі APA, Harvard, Vancouver, ISO та ін.
31

Tsiskaridze, Shota. "Search for avor-changing neutral current top quark decays t—›Hq, with H—›bb, in pp collisions at √s = 8 TeV with the ATLAS detector." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/387229.

Повний текст джерела
Анотація:
Esta tesis presenta la búsqueda de decaimientos del quark top, via corrientes neutras que cambian el sabor, a quarks tipo u (q = u; c) y a el bosón de Higgs del modelo estándar. El análisis busca eventos donde un quark top decae a Wb y el W decae en leptones, mientras que el otro quark top decae a Hq. El estudio se basa en colisiones protón-protón a una energía en el centro de masa de √ s = 8 TeV obtenidas en 2012 con el detector ATLAS del Large Hadron Collider del CERN, usando una muestra de 20.3 fb-1. Los datos corresponden a eventos con un electrón o muon aislado y al menos cuatro jets en el estado final. La búsqueda explota la alta multiplicidad de quarks b que caracterizan la señal, empleando un discriminante basado en la verosimilitud que utiliza las diferencias cinemáticas entre la señal y el fondo (el cual está dominado por eventos tt—›WbWb). No se observan eventos en exceso del fondo esperado. Los límites de un 95% de confianza para el proceso observado (esperado) son de 0.56% (0.42%) para t —›Hc y de 0.61% (0.64%) para t—›Hu. Los límites de esta búsqueda han sido combinados con las búsquedas en los canales con modos de decaimiento H—› y H—›WW*; tt , logrando mejorar significativamente la sensibilidad. Los límites de un 95% de confianza para la combinación observada (esperada) es de 0.46% (0.25%) para t—› Hc y 0.45% (0.29%) para t ! Hu respectivamente. Los límites correspondientes en el acoplamiento | tcH| y | tuH| son de 0.13 (0.10) y 0.13 (0.10) respectivamente. Estos son los límites directos más restringidos en la búsqueda de interacciones tqH hasta el momento.
In this dissertation a search for avour-changing neutral currents in the decay of a top quark to an up-type quark (q = u; c) and the Standard Model Higgs boson, where the Higgs boson decays to bb, is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at √s = 8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb-1. Data are analyzed in the lepton+jets final state, characterized by an isolated electron or muon with moderately high transverse momentum and at least four jets. The search exploits the high multiplicity of b jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by tt—›WbWb decays. No significant excess of events above the background expectation is found. The observed (expected) upper limits on the t—›Hc and t—›Hu branching ratios are 0.56% (0.42%) and 0.61% (0.64%) respectively, at the 95% confidence level. The combination of this search with other ATLAS searches in the H—› and H—›WW*,tt decay modes significantly improves the sensitivity yielding observed (expected) upper limits on the t—›Hc and t—›Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively, at the 95% confidence level. The corresponding combined ob- served (expected) upper limits on the | tcH| and | tuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds to date on tqH interactions measured so far.
Стилі APA, Harvard, Vancouver, ISO та ін.
32

Davidkov, Momchil [Verfasser]. "Supersymmetric flavour changing neutral currents beyond minimal flavour violation / von Momchil Davidkov." 2010. http://d-nb.info/1008485683/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
33

Won, Miguel Daiyen Carvalho. "Flavour-Changing-Neutral-Currents in Top Quark Physics." Doctoral thesis, 2014. http://hdl.handle.net/10316/24325.

Повний текст джерела
Анотація:
Tese de doutoramento em Física, na especialidade de Física Teórica, apresentada ao Departamento de Física da Universidade de Coimbra
This work presents a study on top quark avour-changing-neutralcurrents (FCNC) interaction. These interactions are characterised by a vertex with a top quark and a light u or c quark, together with one of the neutral gauge bosons: gluon, photon and Z boson. They are highly suppressed in the Standard Model (SM), and are therefore a good place to search for physics beyond the SM. We start by presenting a theoretical introduction divided in three chapters. The rst one is dedicated to the subject of collider physics, where the main aspects related to the physics and mathematical background of collider experiments are discussed. A brief account of the SM is then given followed by a more detailed chapter where the subject of E ective Theories and its use in FCNC top quark physics is described. In the following chapters we rst present a study where improvement of FCNC top quark interaction limits were tested in an electronpositron collider. A post LHC scenario where no FCNC physics is found was assumed. In the next chapter we present a study on the well-known asymmetry measured in top quark pair production at the Tevatron, and its deviation in respect to the SM prediction. The study addresses the problem using a set of six dimension e ective operators in order to reproduce this asymmetry. In the following chapter a new Monte Carlo event generator, MEtop, is presented. It is a generator conceived primarily for FCNC direct top events with LO and NLO precision, but it also generates FCNC single top @ LO. The generator allows the user to generate events from three di erent sets of e ective operators. Finally, experimental simulations were performed in order to study the performance of MEtop in FCNC top quark search @ LHC.
FCT - SFRH/BD/45041/2008
Стилі APA, Harvard, Vancouver, ISO та ін.
34

Guedes, Júnior Renato Batista 1968. "Flavour changing at colliders in the effective theory approach." Doctoral thesis, 2008. http://hdl.handle.net/10451/1565.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
35

Peixoto, Ana Paula Pereira. "Search for tZ production via Flavour Changing Neutral Currents with the ATLAS experiment at the LHC." Master's thesis, 2016. http://hdl.handle.net/1822/56022.

Повний текст джерела
Анотація:
Dissertação de mestrado em Física (área de especialização em Física Aplicada)
The subject of the present dissertation is the search for tZ event production by Flavour Changing Neutral Currents (FCNC) through the analysis of data collected by the ATLAS detector of the Large Hadron Collider located in CERN. The FCNC processes are very rare in the Standard Model of Particle Physics since they are not allowed at tree-level and extremely suppressed at loop-level. However, this processes have a higher probability to occur in several models beyond the Standard Model. In this thesis, a search for the production of a top quark and a boson Z via FCNC in a trileptonic topology is discussed. The final state of the tZ production consists in a pair of leptons with opposite sign and same flavour having a mass compatible with the decay of a Z boson, a charged lepton and a neutral lepton classified as coming from the decay of a top quark and finally a jet coming from a bottom quark (b-tagged jet). The analyzed data coming from proton-proton collisions at the centre-of-mass energy of √s = 13 TeV was collected in the data-taking period between July and November of 2015 corresponding to an integrated luminosity of 3.21 fb−1. A complementary study of possible discriminant variables is presented. Through this study, expected upper limits at 95% confidence level on the cross-section of tZ production via FCNC were obtained. An interpretation of these limits in terms of branching ratios for t → qZ and the tZq coupling is also presented.
A presente dissertação tem como objectivo a pesquisa da produção de eventos tZ através de processos de mudança de sabor por correntes neutras recorrendo a uma análise de dados colectados pelo detector ATLAS do Large Hadron Collider localizado no CERN. Os processos de mudança de sabor por correntes neutras são muito raros no Modelo Padrão da Física de Partículas, sendo ausentes a tree-level e extremamente suprimidos a loop-level. No entanto, estes processos têm uma maior probabilidade de ocorrer em vários modelos para além do Modelo Padrão. Neste trabalho é estudada a produção de um quark top e de um bosão Z através de processos de mudança de sabor por correntes neutras numa topologia trileptónica. O estado final desta pesquisa consiste num par de leptões de carga oposta e sabor idêntico com uma massa compatível com o decaimento de um bosão Z, um leptão carregado em conjunto com um leptão neutro provenientes do decaimento de um quark top e finalmente um jacto proveniente de um quark bottom (b-tagged jet). Os dados analisados, relativos a colisões protão-protão a uma energia de centro de massa de √s = 13 TeV, foram obtidos no período de Julho a Novembro de 2015 correspondendo a uma luminosidade integrada de 3.21 fb−1. Um estudo complementar de possíveis variáveis discriminantes é apresentado. Através deste estudo, são obtidos limites superiores esperados com um nível de confiança de 95% na secção eficaz de produção deste processo. Estes limites são interpretados em termos do acoplamento tZq e da fracção de decaimento t → qZ.
Laboratório de Instrumentação e Física Experimental de Partículas, FCT/MEC (Fundação Ciência e Tecnologia /Ministério da Educação e da Ciência), FEDER (Fundo Europeu de Desenvolvimento Regional) for funding my activities this past year, as established by the partnership PT2020 partnership with COMPETE2020 (Autoridade de Gestão do Programa Operacional Competitividade e Internacionalização), by providing me with a research scholarship (Reference LIP/BI-26/2015).
Стилі APA, Harvard, Vancouver, ISO та ін.
36

Weiler, Andreas [Verfasser]. "Minimal flavour violation in the quark and lepton sector and the impact of extra dimensions on flavour changing neutral currents and electroweak symmetry breaking / vorgelegt von Andreas Weiler." 2007. http://d-nb.info/988098083/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
37

Veloso, Filipe Manuel Almeida. "Study of ATLAS sensitivity to FCNC top quark decays." Doctoral thesis, 2008. http://hdl.handle.net/10316/7517.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
38

Jäger, Sebastian [Verfasser]. "Supersymmetric SO(10) unification and flavor changing weak decays / Sebastian Jäger." 2003. http://d-nb.info/969864647/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
39

Poschenrieder, Anton [Verfasser]. "The littlest Higgs and its phenomenological implications for flavor changing neutral currents and lepton flavor violating processes / Anton Poschenrieder." 2007. http://d-nb.info/988908255/34.

Повний текст джерела
Стилі APA, Harvard, Vancouver, ISO та ін.
40

Lee, Yun-Han, and 李昀翰. "Search for top decays through flavor changing neutral current process, t→Z+q, in pp collisions at √s=8 TeV." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/79701030770203938456.

Повний текст джерела
Анотація:
碩士
國立臺灣大學
物理研究所
101
In the standard model, cross-generation interactions mediated by Z bosons, known as the flavor-changing neutral current (FCNC), are highly suppressed. For top quark FCNC decay, the cross-section is far below the experimental limit. However, other models predict much higher cross-sections, and some of them are even within reach. Therefore, using the data sample corresponding to an integrated luminosity of 19.5 fb^−1 proton-proton collisions at a center-of-mass energy 8TeV , collected with the CMS detector at the LHC, we performed the search with the decay chain t¯t to Wb+Zq, where W decays to a charged lepton and a neutrino and Z decays to two charged leptons. The data-driven analysis using b-tagging method is performed with the estimated background being 3.08±0.85±0.76, which is consistent with the estimation of Monte-Carlo method. One event is observed in the data which is consistent with the expected background, and the upper limit of the branching fraction for t to Z+q is calculated as 0.06% at the 95% confidence level.
Стилі APA, Harvard, Vancouver, ISO та ін.
Ми пропонуємо знижки на всі преміум-плани для авторів, чиї праці увійшли до тематичних добірок літератури. Зв'яжіться з нами, щоб отримати унікальний промокод!

До бібліографії