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Dissertations / Theses on the topic 'Supersymmetric Particles'
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Shao, Shu-Heng. "Supersymmetric Particles in Four Dimensions." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493285.
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In this dissertation we study supersymmetric particles in four spacetime dimensions and their relations to other physical observables.
For a large class of four-dimensional N=2 systems, the supersymmetric particles are described by the ground states of certain quiver quantum mechanics in the low energy limit. We derive a localization formula for the index of quiver quantum mechanics with four supercharges. Our answer takes the form of a residue integral on the complexified Cartan subalgebra of the gauge group. The wall-crossing phenomenon appears as discontinuities in the value of the residue integral as the integration contour is varied.
We then move on to study the ground states in the Kronecker model of quiver quantum mechanics. This is the simplest quiver with two gauge groups and bifundamental matter fields, and appears universally in four-dimensional N=2 systems. The ground state degeneracy may be written as a multi-dimensional contour integral, and the enumeration of poles can be simply phrased as counting bipartite trees. We solve this combinatorics problem, thereby obtaining exact formulas for the degeneracies of an infinite class of models. For large ranks, the ground state degeneracy is exponential with the slope being a modular function that we are able to compute at integral values of its argument. We also observe that the exponential of the slope is an algebraic number and determine its associated algebraic equation explicitly in several examples. The speed of growth of the degeneracies, together with various physical features of the bound states, suggests a dual string interpretation.
In the last part of the dissertation, we conjecture a precise relationship between a limit of the superconformal index of four-dimensional N=2 field theories, which counts local operators, and the spectrum of BPS particles on the Coulomb branch. We verify this conjecture for the case of free field theories, N=2 QED, and SU(2) gauge theories coupled to matter. Assuming the validity of our proposal, we compute the superconformal index of all Argyres-Douglas theories. Our answers match expectations from the connection of Schur operators with two-dimensional chiral algebras.<br>Physics
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Lepeintre, François. "Supersymmetric models of flavor /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9699.
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Gascon-Shotkin, Susan Mary. "Search for supersymmetric particles from Z decays." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37756.
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Karamov, Sergey Alexandrovich Catterall Simon. "Supersymmetric theories on the lattice." Related Electronic Resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2003. http://wwwlib.umi.com/cr/syr/main.
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Hoover, Douglas Allan. "Supersymmetric large extra dimensions." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32520.
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In this thesis we examine the viability of a recent proposal, known as Supersymmetric Large Extra Dimensions (SLED), for solving both the cosmological constant and the hierarchy problems. Central to this proposal is the requirement of two large extra dimensions of size r_c ~ 10 micrometres together with a low value for the higher-dimensional scale of gravity, M_* ~ 10 TeV. In order not to run into immediate conflict with experiment, it is presumed that all fields of the Standard Model are confined to a four-dimensional domain wall (brane). A realization of the SLED idea is achieved by relying on the 6D supergravity of Nishino and Sezgin (NS), which is known to have 4D-flat compactifications. When work on this thesis first began, there were many open questions which are now answered either partially or completely. In particular, we expand on the known solutions of NS supergravity, which now include: warped compactifications having either 4D de Sitter or 4D anti-de Sitter symmetry, static solutions with broken 4D Lorentz invariance, and time-dependent "scaling'' solutions. We elucidate the connection between brane properties and the asymptotic form of bulk fields as they approach the brane. Marginal stability of the 4D-flat solutions is demonstrated for a broad range of boundary conditions. Given that the warped solutions of NS supergravity which we consider are singular at the brane locations, we present an explicit regularization procedure for dealing with these singularities. Finally, we derive general formulae for the one-loop quantum corrections for both massless and massive field in arbitrary dimensions, with an eye towards applying these results to NS supergravity<br>Cette thèse examine la viabilité d'une approche récente, dite des Dimensions Supplémentaires Larges Supersymétriques (Supersymmetric Large Extra Dimensions, or SLED), qui propose une solution au problème de la constante cosmologique et à celui de la hiérarchie. Un aspect central de cette approche est l'existence de deux dimensions supplémentaires de grande taille r_c ~ 10 micromètres, et la faible valeur de l'échelle de gravité, M_* ~ 10 TeV. Afin d'éviter un conflit immédiat avec l'expérience, tous les champs du Modèle Standard sont supposés être confinés dans les quatre dimensions observées (i.e. sur une brane). Une implémentation de cette idée de SLED est realisée par le biais de la supergravité 6D de Nishino et Sezgin (NS), dont on sait qu'elle a des compactifications 4D-plates. Un certain nombre de questions, laissées ouvertes lorsque cette thèse à débutée, sont à présent partiellement ou complètement résolues. En particulier, nous étendons les solutions connues de la supergravité NS; elle incluent à present: compactifications déformées ayant la symétrie de Sitter ou anti-de Sitter 4D, solutions statiques avec invariance de Lorentz 4D brisée, et solutions d'échelle ("scaling'') dépendentes du temps. La relation entre les propriétés des branes et la forme asymptotique des champs de bulk lorsqu'ils approchent la brane est mise en lumière et expliquée. La stabilité marginale des solutions 4D-plate est démontrée pour une large classe de conditions de bord. Etant donné que les solutions déformées de la supergravité NS que l'on considère sont singulières à l'emplacement de la brane, une procédure explicite de rég
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Goodyear, Stephen Geoffrey. "Lattice and supersymmetric field theories." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/12044.
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Kittel, Olaf. "CP violation in production and decay of supersymmetric particles." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975015591.
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Tylmad, Maja. "Search for Weakly Produced Supersymmetric Particles in the ATLAS Experiment." Doctoral thesis, Stockholms universitet, Fysikum, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-108060.
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The Large Hadron Collider located at CERN is currently the most powerful particle accelerator and ATLAS is an experiment designed to exploit the high energy proton-proton collisions provided by the LHC. It opens a unique window to search for new physics at very high energy, such as supersymmetry, a postulated symmetry between fermions and bosons. Supersymmetry can provide a solution to the hierarchy problem and a candidate for Dark Matter. It also predicts the existence of new particles with masses around 1 TeV, thus reachable with the LHC. This thesis presents a new search for supersymmetry in a previously unexplored search channel, namely the production of charginos and neutralinos directly decaying to electroweak on-shell gauge bosons, with two leptons, jets, and missing transverse momentum in the final state. The search is performed with proton-proton collision data at a center of mass energy of √s = 8 TeV recorded with the ATLAS experiment in 2012. The design of a signal region sensitive to the new signal is presented and a data driven technique to estimate the Z+jets background is developed. Precise measurements of hadronic jet energies are crucial to search for new physics with ATLAS. A precise energy measurement of hadronic jets requires detailed knowledge of the pulse-shapes from the hadron calorimeter signals. Performance of the ATLAS Tile Calorimeter in this respect is presented using both pion test-beams and proton–proton collision data.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2 and Paper 4: Technical report from the ATLAS experiment.</p>
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Gallant, Colin B. "Supersymmetric ward identities : a diagrammatic analysis of QCD." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27320.
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The purpose of this work is to use the spinor helicity technique in conjunction with supersymmetry to generate tree-level supersymmetric Ward identities for component fields in the pure gauge sector of a supersymmetric non-Abelian vector field. Using the operator formalism with supersymmetric transformations, relations are found among processes containing different numbers of gluinos. Explicit calculations are made for the four-point functions as a demonstration of this approach. To further separate these relations, off-shell calculations are made from which a diagrammatic algorithm is derived. This algorithm is shown to reproduce the standard relations among processes. Explicit calculations using the algorithm are then presented for the four-point functions. In addition, the algorithm is shown to separate the standard relations into subsets of identities.
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Nadeau, Raymond. "Two-loop effective potential of supersymmetric quantum electrodynamics." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75872.
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The formalism of effective potential method is first studied for usual field theory and extended to supersymmetric field theory. The specific case of supersymmetric quantum electrodynamics is then introduced. The superfields are shifted as required by Weinberg's method for the evaluation of effective potentials and superpropagators are derived with the method developed by Helayel-Neto for cases where supersymmetry is explicitly broken. Then, the one and two loop corrections to the effective potential may be calculated. These corrections are seen to be complex everywhere but at the minimum of the potential. Tile theory is then renormalized in a modified minimal substraction scheme and a finite expression is finally obtained for the effective potential. Thereon, the renormalized coupling constant and the $ beta$-function are calculated.
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Marjanovic, Marija. "Search for strongly produced supersymmetric particles with the ATLAS detector and interpretation in the pMSSM." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS096/document.
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Cette thèse a été effectuée dans le cadre de la recherche de la supersymmetrie (SUSY) avec 20.3 fb^{-1} de collisions proton-proton délivrées par le LHC et collectées par le détecteur ATLAS à sqrt{s} = 8 TeV. Si SUSY est réalisée dans la nature, des squarks (partenaires des quarks) et des gluinos (partenaires des gluons) devraient être produits à cette énergie, et on attend à ce qu'ils se désintègrent en états finaux sans electron ni muon, plusieurs jets et de l'énergie transverse manquante (due à la production de la particule SUSY la plus légère (LSP) qui traverse le détecteur sans être observée). La première partie de cette thèse consiste à définir deux régions de validation utilisées dans la procédure finale de fit visant à évaluer le bruit de fond provenant des bosons W et des top quarks qui se désintègrent en leptons tau. A partir de ce fait, et comme on n'a observé aucun excès, on dérive des limites sur les masses des particules dans des modèles simplifiés ou dans des modèles SUSY avec peu de paramètres. Une limite d'exclusion à 95% de niveau de confiance sur la masse des gluinos a été déterminée à 1330 GeV pour le modèle simplifié avec un gluino et un neutralino sans masse. Dans le cadre de mSUGRA/CMSSM avec tan beta = 30, A_0 = -2m_0 et mu > 0, les squarks et gluinos sont exclus pour des masses inférieures à 1700 GeV. L'ajout d'un véto sur les évènements avec les leptons tau est aussi explorée et l'impact sur l'exclusion a été évaluée.Le deuxième partie de cette thèse a été effectuée dans le cadre du modèle phénoménologique minimal supersymmétrique (pMSSM) où l'interprétation des résultats de l'analyse 0-lepton mentionnée ci-dessus, ainsi que les résultats d'autres analyses d'ATLAS, a été menée à bien. Le choix des paramètres et de leur domaine d'exploration a été faite sur la base de résultats non-SUSY comme les désintégrations rares des mésons B, la masse de boson de Higgs, les limites de recherche directe de la matière noire et la limite sur la densité de matière noire de l'Univers. La contribution de cette thèse commence par la validation de la sélection des évènements au niveau truth et reconstruit. Comme cette analyse est la plus contraignante dans le pMSSM, cette validation est faite avec une attention particulière. Les contraintes obtenues avec toutes les analyses sur les masses des différentes particules SUSY sont décrites, en particulier pour les squarks, gluinos et neutralinos. Les résultats sont discutés pour les types des LSP différents: bino, wino et Higgsino. Enfin, les résultats de l'analyse 0-lepton seule sont décrits et expliqués, à la fois pour les masses des sparticules et pour les valeurs des paramètres du pMSSM, puisque l'analyse 0-lepton est la seule qui permet de mettre des limites en se basant sur une procédure statistique bien définie<br>This thesis has been performed in the context of the search for supersymmetry (SUSY) with the 20.3 fb^{-1} of LHC proton-proton collision data collected with the ATLAS detector at $sqrt{s}$ = 8 TeV. If SUSY is present in nature, squarks (partners of quarks) and gluinos (partners of gluons) are expected to be produced copiously at this energy, leading to events which main signature is no electron nor muon, a large number of jets and missing transverse energy (from the production of the lightest supersymmetric particle (LSP) leaving the detector unseen) denoted the 0-lepton analysis. The first part of the work presented in this thesis concentrates on the definition of Validation Regions used in the final fitting procedure to better assess the background coming from W-boson and top quark decays to tau leptons. From this fit, and since no excess has been observed, upper limits on various supersymmetric particles production have been derived within simplified models or SUSY models with low number of parameters. The exclusion limits at the 95% confidence level on the mass of the gluino has been set to 1330 GeV for a simplified model incorporating only a gluino and the (massless) lightest neutralino. In the mSUGRA/CMSSM models with $tanbeta=30$, $A_0=-2m_0$ and $mu>0$, squarks and gluinos of equal mass have been excluded for masses below 1700 GeV. A possible addition of a veto on the events containing tau leptons was also explored by assessing its impact on the exclusion reach of the analysis.The second part of this thesis has been done under the 19 parameters phenomenological Minimal Supersymmetric Standard Model (pMSSM) interpretation which not only uses the results of the above mentioned 0-lepton analysis but also other ATLAS searches results. The choice of the parameters and their range of exploration has been done on the basis of non-SUSY experimental results such as the rare B-decays, the mass of the SM Higgs boson, the limits from direct DM searches and the upper limit on the cold dark matter energy density of the Universe. The contribution of this thesis starts with the validation of the event selection at the truth and reconstructed levels. Knowing that this is the most constraining ATLAS analysis in the pMSSM parameter space, those checks have been performed with particular care. The constraints obtained with all the analyses on the various sparticle masses are described afterwards, concentrating on squarks, gluinos and neutralinos. The results are discussed for the different natures of the LSP: bino, wino and higgsino. Finally the 0-lepton-only results are described and further explained, first on sparticle mass planes and later on the pMSSM parameters, since only the 0-lepton analysis leads to a well defined statistical procedure that allows to derive properly all those results
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Tiesi, Alessandro. "Higgs boson masses in a non-minimal supersymmetric model." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249922.
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Siggia, Vincent R. "An Introduction to Supersymmetric Quantum Mechanics." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5884.
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In this thesis, the general framework of supersymmetric quantum mechanics and the path integral approach will be presented (as well as the worked out example of the supersymmetric harmonic oscillator). Then the theory will be specialized to the case of supersymmetric quantum mechanics on Riemannian manifolds, which will start from a supersymmetric Lagrangian for the general case and the special case for S2. Afterwards, there will be a discussion on the superfield formalism. Concluding this thesis will be the Hamiltonian formalism followed by the inclusion of deforma- tions by potentials.
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Kuester, H. [Verfasser]. "Searches for supersymmetric particles with the Cello detector at Petra / H. Kuester." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1196629021/34.
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Giacomelli, Simone. "Confinement and Duality in Supersymmetric Gauge Theories." Doctoral thesis, Scuola Normale Superiore, 2013. http://hdl.handle.net/11384/85865.
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Williams, Sarah Louise. "Searching for weakly produced supersymmetric particles using the ATLAS detector at the LHC." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648785.
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Cappello, Gigi. "Search for supersymmetric particles in opposite sign dilepton events with the CMS detector." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1427.
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In this thesis a search for supersymmetric particles in the data collected by CMS at center of mass energy of 7 TeV is presented. The search is focused on the selection
of events characterized by pairs of opposite sign electrons or muons. This particular exclusive signature (which we refer to as opposite sign dilepton signature) has a very good background rejection power and would permit systematic studies of the supersymmetric particles produced, once a sufficient amount of them is collected.
The bulk of the analysis consists on the isolation of the events of new physics, through the performance of some selection cuts on properly chosen discriminating variables. Even if, after this step, most part of the standard model background is actually rejected, an estimate of the background events still surviving (mainly top pairs) is mandatory. The
control of any residual background is here made using a particular data-driven method, involving many discriminating variables. Using this technique, we were able to set exclusion limits in the cMSSM plane at 95% of confidence level, using a Bayesian approach.
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Coughlan, G. D. "Cosmological inflation and supersymmetric particle physics : Implications for the big-bang theory." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355735.
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Ren, Huan. "Search for supersymmetric particles in final states with multi-leptons with the ATLAS detector." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0235/document.
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Le grand collisionneur de Hadron (LHC), plus grand accelerateur au monde situe au CERN (Organisation Europeenne pour la recherche Nucleaire), produit des collisions proton proton collectees depuis 2009 par le detecteur ATLAS a une energie atteignant 8TeV dans le centre de masse en 2012 (Run1) et 13 TeV en 2015 et 2016 (Run2). Les modeles theoriques SuperSymetrique (SUSY), extension du Modele Standard (SM), relient chaque boson (de spin entier) a un fermion specifique (de spin demi entier) comme super partenaire. De nouvelles particules elementaires sont ainsi introduites. Apres une breve presentation du SM et des principaux modeles SUSY, the LHC et le detecteur ATLAS sont decrits suivi par une etude de performance sur l'isolation des taus. La partie principale du memoire decrit ensuite en detail deux recherches de particules SUSY avec le detecteur ATLAS et les resultats obtenus.La premiere recherche decrite est celle de production directe de stau avec un etat final a deux tau de signes opposes et plusieurs jets dans des collisions pp a 8TeV et une luminosite integree de 20.1 fb-1. Des techniques d’analyse multi variables ont ete utilisees pour ameliorer la sensibilite. Aucun exces significatif par rapport au SM n’a ete observe. Dans une recherche directe de stau, un signal avec m(LSP) = 0 GeV et m(stau) = 100 GeV est exclus.La deuxieme recherche presentee est celle de la production forte de squarks et de gluions avec des etats finaux, a deux leptons de memes signes ou a trois leptons, associees a des jets dans des collisions proton-proton a $\sqrt{s} = 13 TeV$ et une luminosite integree de 13.2 fb-1. Aucun exces significatif par rapport au SM n’a ete observe<br>The Large Hadron Collider (LHC), largest collider located at CERN (European Organization for Nuclear Research). produces proton-proton collisions collected by the ATLAS detector since 2009 at a collision center of mass energy up to 8 TeV before 2012 (Run1) and 13 TeV in 2015 and 2016 (Run2). Supersymmetry (SUSY) theory models, extension of the Standard Model (SM), link each boson (of integer spin) to a certain fermion (of half integer spin) as super-partner. New elementary particles are then introduced.After a brief presentation of the Standard Model and of the main SUSY models, the LHC and the ATLAS detector are described followed by a performance study on tau isolation. The main part of the document finally describes in details two searches for SUSY particles with the ATLAS detector and the obtained results.The first one is a search for direct stau production with final state of two opposite sign taus and multi-jets in 8 TeV pp collision and 20.1 fb-1 integrated luminosity. Multivariable analysis techniques are used to improve the sensitivity. No significant excess over the SM expectation was observed. Upper-limit was set on the cross-section of the signal models. For “direct stau” search, we excluded the signalpoint with m(LSP) = 0 GeV and m(stau) = 100 GeV.The second one is a search for squarks and gluinos strong production in final states with jets and two same-sign leptons or three leptons at 13 TeV and 13.2 fb-1 integrated luminosity. No significant excess over the SM expectation was observed. Upper-limit was set on the cross-section of all the models involved. Region with gluino mass up to 1.7 TeV have been excluded
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Galea, Raphael. "A search for R-parity violating supersymmetric particles at HERA using the ZEUS detector." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58634.pdf.
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Broggio, Alessandro [Verfasser]. "Applications of SCET to the pair production of supersymmetric particles at hadron colliders / Alessandro Broggio." Mainz : Universitätsbibliothek Mainz, 2013. http://d-nb.info/1035421070/34.
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Khan, Afzal Mohammed. "Limits on the masses of supersymmetric particles from UA1 experiment at the CERN pp⁻ collider." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47502.
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Wens, Vincent. "Of N=1 supersymmetric gauge theories and localization." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210272.
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In this thesis, we study certain non-perturbative aspects of N=1 gauge theories. We show how to compute the expectation values of chiral operators (i.e. those that preserve the anti-chiral supercharges) exactly from a first-principle approach based on the path integral over the microscopic fields. <p><p>The text is divided into two parts. The first one consists of an original introduction to the tools that underlie the researches and results obtained during this thesis. After a general introduction, we present some methods to obtain exact results. Covered topics include instantons, N=2 supersymmetry and localization,N=1 supersymmetry and holomorphy, and finally the Dijgraaf-Vafa matrix model formalism and the perturbative generalized Konishi anomaly equations. These preliminaries were chosen to enlighten the presentation of our results. A brief overview of our results is then. This includes localization in some N=1 gauge theories, its applications to the computation of chiral correlators as well as a non-perturbative discussion of the generalized Konishi equations and of the Dijkgraaf-Vafa glueball superpotential. We insist on the ideas and the results, postponing the details for the second part, which consists of a faithful reproduction of the papers published during this thesis and in which the author has been involved. /<p><p>Dans cette thèse, nous étudions certains aspects non-perturbatifs des théories de jauge supersymétriques N=1. Plus précisemment, nous montrons comment les valeurs moyennes des opérateurs chiraux (qui préservent la moitié des supercharges) dans les vides quantiques peuvent être calculées sans approximations, à partir d'une approche basée sur l'intégrale fonctionnelle sur les champs microscopiques. <p><p>Ce mémoire est divisé en deux parties. La première consiste en une introduction à l'approche microscopique des théories de jauge supersymétriques. Une grande fraction de celle-ci est dédiée à la présentation des concepts et méthodes qui sont à la base du développement de ce formalisme et de nos recherches. Ceci inclut les instantons, la supersymétrie N=2 et la localisation dans l'intégrale fonctionnelle, la supersymétrie N=1 et l'holomorphie, et enfin l'approche de Dijkgraaf-Vafa basée sur un modèle de matrices et les équations d'anomalie généralisées de Konishi. Ensuite, nous présentons le formalisme microscopique et les résultats obtenus durant cette thèse. Nous expliquons comment utiliser la technique de localisation dans certaines théories de jauge N=1 et comment l'appliquer au calcul des valeurs moyennes des opérateurs chiraux. Nous discutons également de façon non-perturbative les équations d'anomalie généralisées de Konishi et le superpotentiel de Dijkgraaf-Vafa. La plupart des résultats exacts connus dans les théories de jauge N=1 sont reproduits, dont la condensation des gluinos et la brisure de la symétrie chirale.<p>Nous insistons sur les idées et les résultats plutôt que sur les détails techniques. Ceux-ci sont décrits dans la seconde partie de ce mémoire, qui consiste en une reproduction fidèle des travaux publiés durant cette thèse.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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CARRA, SONIA. "SEARCH FOR ELECTROWEAK PRODUCTION OF SUPERSYMMETRIC PARTICLES AT THE LHC RUN 2 WITH THE ATLAS DETECTOR." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/608194.
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Two closely related searches for the electroweak production of Supersymmetric particles are presented in this manuscript.
The analyses are based on the proton-proton collision data from the Large Hadron Collider Run 2, with a center-of-mass energy of 13 TeV, collected by the ATLAS experiment.
Different Supersymmetric signal models are considered. The first search targets the pair production of either the Supersymmetric partners of the leptons (sleptons) or the $W$ boson and charged Higgs boson super-partners (charginos). In the latter case, the decay of charginos via sleptons is assumed. The search uses data collected by ATLAS between 2015 and 2016, with an
integrated luminosity of 36.1 fb$^{-1}$. The second search targets the direct production of chargino pair with $W$ boson mediated decay. The analysis for the observation of the process was performed using the data collected by ATLAS between 2015 and 2017, reaching an integrated luminosity of 80.5 fb$^{-1}$.
The signature, common to all the SUSY signal models considered, consists of two charged leptons (electrons or muons) and missing transverse energy. No significant fluctuation above the Standard Model prediction was observed in the analyses.
New exclusion limits, tighter than the previously available results, were placed on the masses of the SUSY particles: slepton masses up to 500 GeV are excluded at 95%~CL. Chargino masses up to 700 GeV are excluded in the case of the decay mediated by a slepton, while considering the $W$ boson mediated decay the limit on the chargino mass is 410 GeV.
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Rizzi, Chiara. "Searches for supersymmetric particles in final states with multiple top and bottom quarks with the ATLAS detector." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/665182.
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En esta tesis se presentan dos búsquedas de Supersimetría en colisiones protón-protón en el Gran Colisionador
de Hadrones (LHC, por sus siglas en inglés) del CERN, centradas en modelos que dan lugar a
la producción de múltiples quarks top o quarks bottom en el estado final.
La primera búsqueda tiene como objetivo la producción de pares de gluinos, donde cada gluino de
desintegra a través de un squark top (modelo Gtt) o un squark bottom (modelo Gbb) en una pareja
de quarks top-antitop o bottom-antibottom, respectivamente, y un neutralino, que es la partícula supersimétrica
más ligera (LSP, por sus siglas en inglés). Cada quak top a su vez se desintegra en un bosón W
y un quark bottom. Consecuentemente, el estado final se caracteriza por una alta multiplicidad de bottom
jets (b-jets), que son chorros de partículas resultantes de la hadronización de quarks bottom, así como un
alto momento transverso faltante (Emiss
T ) debido a que la LSP escapa sin ser detectada.
La segunda búsqueda tiene como objetivo la producción de pares de higgsinos en el contexto de un
modelo GGM, en el cual cada higgsino se desintegra en el bosón de Higgs del Model Estándar y un
gravitino, que en este caso juega el papel de la LSP. Esta búsqueda se centra en sucesos donde ambos
bosones de Higgs se desintegran en parejas de quarks bottom-antibottom, de nuevo dado lugar a estados
finales con múltiples b-jets. Este es el primer análisis en ATLAS optimizado para esta signatura, la cual
había sido considerada previamente en búsquedas llevadas a cabo por la colaboración CMS.
Ambas búsquedas en esta tesis usan los datos recopilados por el experimento ATLAS en el LHC entre
el 2015 y el 2016, a una energía del centro de masas de ps = 13 TeV, correspondiente a una luminosidad
integrada de 36.1 fb−1. La búsqueda de gluinos, sin optimización adicional, ha sido extendida usando los
datos recopilados en el 2017, resultando en una luminosidad integrada total de 79.8 fb−1.
No habiendo encontrado un exceso significativo de sucesos sobre la predicción del Modelo Estándar
en ninguna de las regiones de búsqueda, los resultados han sido usados para establecer límites superiores
a la producción de partículas supersimétricas. La primera búsqueda excluye a un nivel de confianza del
95% masas del gluino de hasta 2.25 TeV para el modelo Gtt y de hasta 2.17 TeV para el modelo Gbb,
en ambos casos para masas del neutralino menores que 800 GeV. La segunda búsqueda excluye masas
del higgsino en el rango de 240–880 GeV, asumiendo que<br>This dissertation presents two searches for Supersymmetry in proton-proton collisions at CERN’s Large
Hadron Collider (LHC), targeting signal models that lead to the production of multiple top quarks or
bottom quarks in the final state.
The first search targets gluino pair production, where each gluino decays through a top squark (Gtt
model) or a bottom squark (Gbb model) to a top-antitop quark pair or a bottom-antibottom quark pair,
respectively, and a neutralino, which is the Lightest Sypersymmetric Partner (LSP). Each top quark in turn
decays to aW boson and an a bottom quark. Thus, the final state is characterized by a high multiplicity of
bottom jets, which are collimated sprays of particles originating from the hadronization of bottom quarks,
and missing transverse momentum (Emiss
T ) from the LSP that escapes the detection.
The second search targets a GGM model of higgsino pair production, where each higgsino decays to
a Standard Model Higgs boson and a gravitino, which in this case plays the role of the LSP. This search
focuses on the decay of the two Higgs bosons to bottom-antibottom quark pairs, yielding again final states
with multiple b-jets. This is the first ATLAS analysis targeting this signature, which had been previously
considered in searches performed by the CMS Collaboration.
Both searches in the thesis use the data collected by the ATLAS experiment at the LHC between 2015
and 2016, at a center-of-mass energy ps = 13 TeV, corresponding to an integrated luminosity of 36.1
fb−1. The gluino search, without further reoptimization, is also extended using the data collected in 2017,
for a total integrated luminosity of 79.8 fb−1.
No significant excess of events above the Standard Model expectation is observed in any of the search
regions, and the results are used to set upper limits on the production of supersymmetric particles. The
first search excludes at 95% confidence level gluino masses up to 2.25 TeV for the Gtt model and up
to 2.17 TeV for the Gbb model, in both cases for neutralino masses below 800 GeV. The second search
excludes higgsino masses in the range 240–880 GeV, assuming that the higgsino decays exclusively to a
Higgs boson and a gravitino.
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Tornambè, Peter [Verfasser], and Gregor [Akademischer Betreuer] Herten. "Search for supersymmetric particles in final states with leptons, jets and missing transverse energy with the ATLAS detector." Freiburg : Universität, 2019. http://d-nb.info/1179075277/34.
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BALLABENE, ERIC. "SEARCH FOR ELECTROWEAK PRODUCTION OF SUPERSYMMETRIC PARTICLES IN COMPRESSED MASS SPECTRA WITH THE ATLAS DETECTOR AT THE LHC." Doctoral thesis, Università degli Studi di Milano, 2022. https://hdl.handle.net/2434/943307.
Full textAbstract:
In questa tesi, sono presentate due analisi che cercano la produzione di particelle supersimmetriche attraverso l'interazione elettrodebole: la ricerca di chargini, dove i chargini prodotti decadono in bosoni W e neutralini, e la ricerca di tracce displaced, ossia di tracce cariche spostate dal vertice di collisione primario, provenienti dai decadimenti di higgsini in pioni. Queste ricerche sono effettuate in spettri di massa compressi, dove la differenza di massa tra la particella subito più pesante di quella più leggera e quella più leggera è relativamente piccola. Queste ricerche usano dati provenienti dalle collisioni protoni-protoni raccolti con un'energia nel centro di massa di 13 TeV con il rivelatore ATLAS presso LHC.
Nella ricerca di chargini, la differenza di massa considerata tra i chargini e i neutralini è vicina alla massa del bosone W. In tale spazio fasi, la produzione di coppie di chargini è cinematicamente simile a quella del fondo WW, il che rende sperimentalmente difficile separare il segnale dei chargini dal fondo WW. Lo stato finale considerato è costituito da due leptoni provenienti dai decadimenti leptonici dei bosoni W, momento trasverso mancante e assenza di attività adronica, mentre tecniche di machine learning avanzate sono impiegate per separare il segnale supersimmetrico dai fondi. Masse di chargini fino a 140 GeV sono escluse al 95% di livello di confidenza nel caso di una differenza di massa minore di circa 100 GeV. I risultati ottenuti soprassiedono i precedenti risultati di ATLAS in regioni particolarmente interessanti dove la produzione di coppie di chargini si sarebbe potuta nascondere dietro il simile fondo WW.
Nella ricerca di tracce displaced, la differenza di massa tra le particelle supersimmetriche prodotte e i neutralini più leggeri scende fino a 0.3 GeV. La segnatura sperimentale è costituita da un getto, momento trasverso mancante e una traccia carica a basso momento con un'origine spostata dal punto di collisione; quest'ultimo elemento è la prima volta che viene usato in una ricerca di questo tipo ad un collisionatore adronico. I risultati mostrano che l'analisi ha sensitività per escludere diverse ipotesi di segnale per masse di higgsini fino a 175 GeV se nessun eccesso è osservato nei dati. Per masse inferiori, la sezione d'urto più grande permette di ottenere significanze più elevate per diversi scenari di differenze di massa. Tutte queste ipotesi di segnale non sono ancora state esplorate da nessuna analisi esistente dei dati di LHC.<br>In this thesis, two analyses searching for the production of supersymmetric particles through the electroweak interaction are presented: the chargino
search, targeting the pair production of charginos decaying into W bosons and neutralinos, and the displaced track search, looking for mildly displaced charged tracks arising from the decays of higgsinos into pions. These searches target compressed phase spaces, where the mass difference between the next-to-lightest and lightest supersymmetric particle is relatively small. The searches use proton-proton collision data collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC.
In the chargino search, the targeted difference in mass between charginos and neutralinos is close to the mass of the W boson. In such phase space, the chargino pair production is kinematically similar to the WW background, which makes the chargino signal experimentally challenging to be discriminated from the WW background. A final state with two leptons from the leptonic decays of the W bosons, missing transverse momentum and no hadronic activity is considered, while advanced machine learning techniques are adopted to separate the supersymmetric signal from the backgrounds.
Chargino masses up to about 140 GeV are excluded at 95% confidence level in the case of a mass splitting between chargino and neutralino down to about 100 GeV. The results supersede the previous ATLAS results in particularly interesting regions where the chargino pair production could have hidden behind the looking-alike WW background.
In the displaced track search, the difference in mass between the produced supersymmetric particles and the lightest neutralinos goes down to 0.3 GeV.
The experimental signature is one jet, missing transverse momentum, and a low momentum charged track with an origin displaced from the collision point, the last element being the first time it is used in a search of this kind at a hadron collider. The results show that the analysis has the sensitivity to exclude different signal hypotheses for higgsino masses up to 175 GeV if no excess is observed in data. For lower masses, the larger signal cross-section allows to achieve higher significance values for different mass splitting scenarios. All these signal hypotheses have not been probed by any existing analysis of LHC data.
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Jansova, Markéta. "Search for the supersymmetric partner of the top quark and measurements of cluster properties in the silicon strip tracker of the CMS experiment at Run 2." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE018/document.
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Cette thèse présente trois études différentes basées sur les données de CMS du Run 2. Les deux premières sont des mesures des propriétés des amas dans le trajectographe à pistes de silicium de CMS, liées respectivement aux particules hautement ionisantes (HIP) et au partage de charge entre les pistes voisines (également appelé diaphonie). Le dernier sujet abordé dans ce document est la recherche du partenaire supersymétrique du quark top, appelé stop. Une augmentation de l’inefficacité de reconstruction des hits dans le trajectographe à pistes de silicium de CMS a été observée au cours des années 2015 et 2016. Les particules hautement ionisantes ont été identifiées comme une cause possible de ces inefficacités. Cette thèse apporte des résultats qualitatifs et quantitatifs sur l’effet HIP et sa probabilité. Le HIP n’était pas la source la plus importante d’inefficacité et, une fois la source identifiée et corrigée, les nouvelles données révèlent qu’après cette correction, le HIP représente à présent la principale source d’inefficacité. La seconde étude présentée porte sur les conditions utilisées dans la simulation du trajectographe par CMS afin de fournir des résultats réalistes. Ces conditions changent avec les conditions de fonctionnement du trajectographe et évoluent avec le vieillissement du trajectographe résultant des dommages causés par le rayonnement. Nous avons constaté que les paramètres de diaphonie obsolètes avaient une grande incidence sur la forme de l’amas. Dans cette thèse, les paramètres ont été réévalués et il a été confirmé que les nouveaux paramètres améliorent grandement l’accord des amas entre données et simulation. La dernière partie décrit en profondeur la recherche de stop en utilisant les données collectées en 2016 (correspondant à ∫L = 35.9 fb−1) avec un lepton dans l’état final. Aucun excès n’a été observé par rapport aux prédictions attendues par le modèle standard et les résultats ont été interprétés en terme de limites d’exclusion sur des modèles simplifiés<br>This thesis presents three different studies based on the CMS Run 2 data. The first two are measurements of the cluster properties in the CMS silicon strip tracker related respectively to the highly ionizing particles (HIP) and the charge sharing among neighboring strips (also known as cross talk). The last topic discussed in this document is the search for the supersymmetric partner of the top quark, called the stop. An increase in the hit inefficiency of the CMS silicon strip tracker was observed during the years 2015 and 2016. The highly ionizing particles were identified as a possible cause of these inefficiencies. This thesis brings qualitative and quantitative results on the HIP effect and its probability. The HIP was found not to be the largest source of inefficiency at that time and once the source was identified and fixed, the new data revealed that after this fix the HIP now represents the major source of the hit inefficiency. The second study presented in this thesis focuses on the conditions plugged in CMS tracker simulation in order to provide realistic results. These conditions change with the tracker operating conditions and also evolve with tracker ageing resulting from the radiation damage. We identified that the outdated cross talk parameters largely impact the cluster width and seed charge. In this thesis the parameters were remeasured and it was confirmed that the new parameters largely improve the agreement of clusters between data and simulation. The last part describes deeply the stop analysis using data recorded in 2016 (corresponding to ∫L =35.9 fb−1) with single lepton in the final state. No excess was observed in the full 2016 data (∫L = 35.9 fb−1) with respect to the standard model background predictions and therefore exclusion limits in terms of simplified model spectra were derived
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Wittkowski, Josephine. "Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-178287.
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Es werden drei Analysen vorgestellt, die nach elektroschwach produzierten supersymmetrischen Teilchen in Proton-Proton-Kollisionen suchen. Die Kollisionen wurden mit dem ATLAS-Experiment am Large Hadron Collider aufgenommen. Zwei Leptonen (Elektronen oder Myonen), Jets und fehlende transversale Energie werden im Endzustand erwartet. `Simplified Models' werden genauso wie das `phenomenological Minimal Supersymmetric Standard Model' (pMSSM) verwendet, um die Produktion und den Zerfall von Gaugino-Paaren, also Paaren aus Charginos und Neutralinos, zu untersuchen.
Die erste Analyse wird mit ATLAS Daten, die einer integrierten Luminosität von 4.7 fb^-1 entsprechen und im Jahr 2011 bei einer Schwerpunktenergie von sqrt(s)=7 TeV aufgenommen wurden, durchgeführt. Die direkte Produktion von Sleptonen sowie drei weitere Szenarien, in denen Gaugino-Paare über zwischenzeitliche Sleptonen zerfallen, werden untersucht. Besonders hervorgehoben wird die Triggerstrategie. Da kein Überschuss an Ereignissen in den ATLAS Daten beobachtet wird, können beispielsweise die Massen linkshändiger Sleptonen im Bereich von 85 bis 195 GeV mit 95% Konfidenzniveau ausgeschlossen werden. Hierfür wird ein Simplified Model, das die direkte Produktion von Sleptonen annimmt, verwendet, und das Neutralino besitzt eine Masse von 20 GeV.
In einer zweiten Analyse werden 20.3 fb^-1 ATLAS Daten benutzt, die im Jahr 2012 mit sqrt(s)= 8 TeV aufgenommen wurden. Sieben Signalregionen zielen auf supersymmetrische Zerfallsketten ab, in denen zwei Leptonen mit entgegengesetztem Ladungsvorzeichen im Endzustand erwartet werden. Der dominante Standardmodelluntergrund besteht, analog zu der Analyse der 2011er Daten, aus ttbar-, Z/gamma*+jets- und zwei-Boson-Prozessen. Zwei-Lepton-Trigger werden kombiniert um die Ereignisse auszuwählen. Die Ergebnisse entsprechen den Erwartungen des Standardmodells und werden im Rahmen des pMSSM interpretiert. Massen des chi_1^+- können zwischen 100 und 105 GeV, 120 und 135 GeV sowie zwischen 145 und 160 GeV mit 95% Konfidenzniveau für ein masseloses chi_1^0 ausgeschlossen werden. Das Simplified Model für den Prozess chi_1^+ chi_1^- -> W^+ chi_1^0 W^- chi_1^0 -> l^+ nu chi_1^0 l^- nu chi_1^0 wird dazu verwendet. Mit der Simulation der direkten Produktion von Sleptonen in einem weiteren Simplified Model können Sleptonmassen zwischen 90 und 325 GeV ausgeschlossen werden (m_chi_1^0< 30 GeV).
Die dritte Analyse wird ebenfalls mit 2012er Daten durchgeführt. Es wird ein Szenario betrachtet, in dem ein Chargino-Neutralino-Paar über ein W- und ein Higgsboson in einen Endzustand mit zwei gleichnamig geladenen Leptonen, zwei Quarks und zwei leichtesten Neutralinos zerfällt. Der Hauptuntergrund beruht auf Leptonen, die nicht vom primären Zerfallsvertex stammen, und wird mit Hilfe von ATLAS Daten bestimmt. Der Beitrag durch Standardmodell-Prozesse mit zwei Bosonen wird z.B. durch Schnitte auf die invariante Masse der Zerfallsprodukte des Higgsbosons und auf die effektive Masse, das ist die skalare Summe der Transversalimpulse der Leptonen, Jets und der fehlenden Transversalenergie, unterdrückt. Die Ergebnisse dieser Analyse sind noch nicht veröffentlicht. Man erwartet, dass die drei Massenpunkte mit Neutralinomassen unter 10 GeV und Charginomassen unter 150 GeV mit 95% Konfidenzniveau ausgeschlossen werden können.<br>Three analyses searching for electroweakly produced supersymmetric particles in proton-proton collisions are presented. The collisions were recorded by the ATLAS experiment at the Large Hadron Collider. Two leptons (electrons or muons), jets and missing transverse energy are expected in the final states. Simplified models as well as the phenomenological Minimal Supersymmetric Standard Model (pMSSM) are used to study the production and decay of pairs of gauginos, i.e. charginos and neutralinos.
The first analysis is performed with an integrated luminosity of 4.7 fb^-1 of ATLAS data, recorded in 2011 at a centre-of-mass energy of sqrt(s) = 7 TeV. Direct slepton production and three scenarios in which pairs of gauginos decay via intermediate sleptons are addressed. Particular attention is paid to the trigger strategy. No excess is observed in the number of data events. In the simplified model that assumes the direct slepton production, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino.
The second analysis uses 20.3 fb^-1 of ATLAS data recorded in 2012 at sqrt(s) = 8 TeV. Seven signal regions address supersymmetric decay scenarios with two oppositely charged leptons in the final state. The dominating Standard Model background processes are, analogously to the 2011 analysis, ttbar, Z/gamma^*+jets and diboson processes. A combination of dilepton triggers is used to select the events. The results are in agreement with the Standard Model expectations and are interpreted in the context of the pMSSM. chi_1^pm masses between 100 and 105 GeV, 120 and 135 GeV and 145 and 160 GeV can be excluded at 95% confidence level for m_chi_1^0= 0 GeV in the simplified model for which chi_1^+ chi_1^- -> W^+ chi_1^0 W^- chi_1^0 -> l^+ nu chi_1^0 l^- nu chi_1^0. Slepton masses between 90 and 325 GeV can be excluded at 95% CL for a neutralino mass of less than 30 GeV when the direct slepton production is simulated in a simplified model.
A third analysis is also performed on the 2012 data addressing a scenario in which a chargino-neutralino pair decays via a W- and a Higgs boson into a final state with two same-sign leptons, two quarks and two lightest neutralinos. The dominating background is due to non-prompt leptons and is estimated by a data-driven method. The contribution due to diboson background is suppressed e.g. by cuts on the invariant mass of the decay products of the Higgs boson and on the effective mass, which is the scalar sum of the p_T of the leptons, jets and of the missing transverse energy. The results for this analysis are not yet published. The three mass points with the neutralino masses of less than 10 GeV and chargino masses of less than 150 GeV are expected to be excluded at 95% CL.
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Lorenz, Jeanette. "Search for strongly interacting supersymmetric particles decaying to final states with an isolated lepton with the ATLAS detector at the LHC." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-167877.
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Two analyses searching for squarks and gluinos which decay into final states with multiple
jets, an isolated electron or muon and a large missing transverse energy are presented. Both rely on data taken by the ATLAS detector in
pp collisions at a center-of-mass energy of 8 TeV at the LHC during 2012. The first analysis uses a subset of 5.8 fb-1 of this dataset, the other analysis uses the full statistics of 20.3 fb-1.
Both analysis share the same methods regarding the triggers and the background estimation techniques. The two
dominant backgrounds are ttbar and W+jets production. The ttbar
and the W+jets backgrounds are estimated in a semi-data-driven method. The minor QCD multi-jet background is estimated in an entirely
data-driven method. The final background estimates in the analyses are derived in a profile-log-likelihood fit.
None of the analyses sees an excess beyond Standard Model expectations.
The analysis of the partial dataset derives limits in a MSUGRA/CMSSM model with parameters A_0=0, tan(beta) = 10
and mu > 0 and excludes squarks and gluinos with masses below 1.2 TeV for equal squark and gluino masses.
The analysis of the full dataset derives limits in simplified models and in a MSUGRA/CMSSM model with parameters A_0=-2 m_0,
tan(beta) = 30 and mu > 0. Gluinos (squarks) with masses below 1.2 TeV (750 GeV) can be excluded for vanishing LSP masses in simplified models. Gluino masses below 1.2 TeV can be excluded for every m_0 value in the MSUGRA/CMSSM model.
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Shehu, Yusufu. "Search for the electroweak production of supersymmetric particles in three-lepton events at the ATLAS detector with focus on compressed mass spectra." Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/67205/.
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This thesis presents a search for the electroweak production of supersymmetry using the dataset taken by the ATLAS detector at the Large Hadron Collider with √8 = 8 TeV during 2012. Events with three leptons are selected and required to satisfy additional kinematic criteria that define optimised signal regions. In these signal regions, Standard Model processes are discriminated against, whilst retaining a large fraction of events produced by specified compressed supersymmetry scenarios. Compressed refers to near massdegeneracy between the decaying gauginos and the final state gauginos. The expected number of Standard Model events are estimated using a combination of Monte Carlo and data-driven methods, where the predictions are tested against data in specifically designed validation regions. Exclusion limits are then set at 95% confidence level (CL) on via ℓ`L- and via WZ-decay scenarios for the decaying charginos and neutralinos. With the ℓ`L halfway between the decaying charginos and neutralinos and the final state neutralinos, there is a new sensitivity up to 250 GeV. In scenarios with large mass splitting, the decaying chargino and neutralino masses are excluded up to 740 GeV. Looking forward to the 13 TeV data-taking, a search for the electroweak production of supersymmetry with threelepton final states is presented, with a first look at an optimisation strategy to improve sensitivity to charginos and neutralinos.
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Houchu, Ludovic. "Identification of the tau leptons decaying hadronically and search for supersymmetric particles decaying to tau leptons with the CMS detector at LHC." Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/HOUCHU_Ludovic_2008_1.pdf.
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Cette thèse a pour sujet la recherche de particules supersymétriques se désintégrant en leptons tau dans l’expérience CMS auprès du collisionneur LHC. L’analyse porte sur des données simulées de collisions proton-proton à une énergie √s = 14 TeV dans le centre de masse. Le modèle supersymétrique retenu est celui mSUGRA. Les événements d’intérêt contiennent au moins deux leptons tau, une grande énergie transverse manquante et au moins deux jets hadroniques de grandes impulsions issus de la fragmentation d’un quark. Dans un échantillon test de données, des processus autres que ceux du Modèle Standard sont mis en évidence. Préalablement, est effectué un travail d’identification des leptons tau dans leurs modes de désintégration hadroniques : une méthode de discrimination entre les jets hadroniques de tau et ceux issus d’un quark ou d’un gluon est introduite, utilisant des candidats photons ou pions neutres reconstruits et un test sur un rapport de pseudo-vraisemblances<br>This thesis concerns the search for supersymmetric particles decaying to tau leptons in the CMS experiment at LHC collider. The analysis uses simulated data of proton-proton collision at a center-of-mass energy of √s = 14 TeV. The supersymmetric model considered is the mSUGRA. The events of interest contain at least two tau leptons, a large missing transverse energy and at least two high momentum hadronic jets coming from the fragmentation of a quark. An analysis is described, which can possibly discover these events in the presence of all standard model processes. First an effort is made to identify tau leptons decaying hadronically: a method of discrimination between hadronic tau jets and quark or gluon jets is introduced, using reconstructed photon or neutral pion candidates and a pseudolikelihood ratio test
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Marconi, Daniele [Verfasser], and Christian [Akademischer Betreuer] Sander. "Search for Supersymmetric Particles from VBF-like processes with two Tau-Leptons with same sign charges at CMS / Daniele Marconi ; Betreuer: Christian Sander." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1160036012/34.
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Holzbock, Michael [Verfasser], and Alexander [Akademischer Betreuer] Mann. "Searches for electroweak production of supersymmetric particles in compressed mass spectra with the ATLAS detector in LHC Run 2 / Michael Holzbock ; Betreuer: Alexander Mann." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1214593240/34.
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Wittkowski, Josephine [Verfasser], and Dorothee [Akademischer Betreuer] Schaile. "Search for electroweakly produced supersymmetric particles in final states including two charged leptons with the ATLAS experiment at the LHC / Josephine Wittkowski. Betreuer: Dorothee Schaile." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1065611161/34.
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Bogavac, Danijela [Verfasser], and Dorothee [Akademischer Betreuer] Schaile. "Searches for supersymmetric particles decaying to W and Higgs bosons in events with an isolated lepton with the ATLAS detector / Danijela Bogavac ; Betreuer: Dorothee Schaile." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1164376926/34.
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Lorenz, Jeanette [Verfasser], and Dorothee [Akademischer Betreuer] Schaile. "Search for strongly interacting supersymmetric particles decaying to final states with an isolated lepton with the ATLAS detector at the LHC / Jeanette Lorenz. Betreuer: Dorothee Schaile." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1049393201/34.
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Javůrková, Martina [Verfasser], and Gregor [Akademischer Betreuer] Herten. "Measurement of WWW production and search for supersymmetric particles in multi-lepton final states in pp collisions at [square root]8 = 8TeV with the ATLAS detector at the LHC." Freiburg : Universität, 2017. http://d-nb.info/1135907250/34.
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Alstaty, Mahmoud Ibrahim. "Commissioning of the Atlas pixel detector at Run 2 of the LHC, and search for supersymmetric particles with two same-sign leptons or three leptons in the final state." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0322.
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Le LHC, ATLAS, le détecteur à pixels et l’IBL sont décrits dans la première partie de ce mémoire. La mise en oeuvre du détecteur à pixels muni de sa nouvelle couche grâce à l’acquisition de rayons cosmiques juste avant le démarrage du Run 2 du LHC est ensuite présentée. L’analyse comprend l’étude des propriétés des amas de pixels allumés par le passage des rayons cosmiques, ainsi que la comparaison entre les deux technologies de compteurs présentes dans la nouvelle couche, les compteurs planaires et les compteurs 3D utilisés pour la première fois auprès d’un collisionneur. Ces études ont permis de valider les logiciels de reconstruction et d’améliorer la simulation de la nouvelle couche. Les produits d’ionisation créés dans les compteurs par le passage de particules chargées sont déviés de leurs trajectoires naturelles le long du champ électrique des jonctions, par le champ magnétique uniforme dans lequel est plongé le trajectographe d’ATLAS. L’angle de la déviation est appelé angle de Lorentz. La mesure de cet angle est essentielle car il affecte la position mesurée. Cette mesure a été réalisée pour toutes les couches, ainsi que la variation de l’angle de Lorentz en fonction de la température. A la fin du Run 1, aucun excès n’a été observé par-dessus les prédictions du Modèle Standard, et des limites inférieures sur les masses de particules supersymétriques en ont été déduites. Ces limites ont été étendues avec l’analyse montrée ici. Le gluino est ainsi plus lourd que 1.87TeV, tandis que la masse du squark b devrait être plus grande que 700 GeV, sous des hypothèses simplificatrices. Ces résultats constituent des contraintes supplémentaires pour la supersymétrie<br>In the first part of this thesis, the LHC, ATLAS, the Pixel Detector and the IBL are all reviewed. Afterwards, the analysis of first cosmic data collected by the ATLAS Detector after the IBL insertion is presented, as part of the Pixel and IBL commissioning before Run 2 started. The analysis included the study of the Pixel clusters properties, and making comparisons between the two different technologies used in the IBL sensors: the Planar type, and the 3D type which has been used for the first time in a collider experiment. Analyzing the Pixel clusters properties is important to study the detector response after the IBL insertion, in order to insure utilizing the ultimate capabilities of the detector, and to achieve better resolutions for the measurements. The Standard Model (SM) of particle physics describes physical phenomena in the fundamental level with great success. However, it suffers from several shortcomings; for instance, it has no candidate for the dark matter, and it has no solution for the gauge hierarchy problem, motivating the search for new physics beyond the SM theories. On of those theories is Supersymmetry(SUSY), which occupies a primer place in the LHC physics program. At the end of Run-1, no significant excess in data over the SM prediction is observed and limits on the supersymmetric particle masses are set. With this analysis, which is basically an extension of the Run 1 analysis, those exclusion limits are extended and the gluino masses are excluded up to 1.87 TeV, while the sbottom mass should be above 700 GeV when using simplified assumptions. These results provide new constraints on natural SUSY models
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Rammensee, Michael [Verfasser], and Gregor [Akademischer Betreuer] Herten. "Search for supersymmetric particles in final states with jets and missing transverse momentum withthe ATLAS detector = Suche nach supersymmetrischen Teilchen mit dem ATLAS Detektor in Endzuständen mit Jets und fehlender transversaler Energie." Freiburg : Universität, 2013. http://d-nb.info/1123476306/34.
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Benhenni, Amine. "Contrainte sur la brisure de supersymétrie par médiation gravitationnelle." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20210.
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La supersymétrie représente le cadre théorique phare en physique des particules pour prendre la relève du modèle standard. Cependant, en tant que cadre général, il dispose de beaucoup de liberté dans sa mise en oeuvre, notamment au niveau des modèles de brisure. Le travail principal de cette thèse consiste à tenter de réduire l'espace des paramètres par des considérations théoriques, en trouvant un sous-espace réduit dans les modèles de brisure par médiation gravitationnelle, en utilisant les méthodes de minimisation du potentiel effectif développé dans les scénarios dits no-scale<br>Supersymmetry is the most preferred theoretical framework that could replace and complete the standard model of particle physics. However it is hard to distinguish clearly between all the possible models allowed.During this thesis, we tried to reduce the arbitrariness in the choice of some parameters in supergravity breaking models, by looking at minimisation methods introduced in no-scale supergravity scenarios
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Xu, Qingjun. "Precision calculation for supersymmetric particle decays." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=98041332X.
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Allahverdi, Rouzbeh. "Topics in supersymmetric astro-particle physics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ59559.pdf.
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WASAY, MUHAMMED. "Supersymmetric Quantum Mechanics." Thesis, Uppsala University, Theoretical Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126725.
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<p>This Master thesis considers certain aspects of Supersymmetric Quantum Mechanics in the context of Path integral approach. First we state all the basic mathematical structure involved, and carry out some basic Gaussian integrals for both commutative and non-commutative variables. Later in the thesis these simple results obtained are generalized to study the Supersymmetric sigma models on flat and curved space. And we will recover the beautiful relationship between the supersymmetric sigma model and the geometry of the target manifold in the form of topological invariants of the manifold, for the models on curved space.</p>
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Dietrich, Janet [Verfasser], and Gregor [Akademischer Betreuer] Herten. "Search for supersymmetric particles in final states with jets and missing energy with the ATLAS Experiment at the LHC = Suche nach supersymmetrischen Teilchen in Zerfallsendzuständen mit Jet(s) und fehlender Energie mit dem ATLAS Experiment am LHC." Freiburg : Universität, 2010. http://d-nb.info/1123461201/34.
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Riva, Francesco. "Cosmological consequences of supersymmetric flat directions." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:2bc82393-82a8-488e-86d9-e3c292a89887.
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In this work we analyze various implications of the presence of large field vacum expectation values (VEVs) along supersymmetric flat directions during the early universe. First, we discuss supersymmetric leptogenesis and the gravitino bound. Supersym- metric thermal leptogenesis with a hierarchical right-handed neutrino mass spectrum normally requires the mass of the lightest right-handed neutrino to be heavier than about 109 GeV. This is in conflict with the upper bound on the reheating temperature which is found by imposing that the gravitinos generated during the reheating stage after inflation do not jeopardize successful nucleosynthesis. We show that a solution to this tension is actually already incorporated in the framework, because of the presence of flat directions in the supersymmetric scalar potential. Massive right- handed neutrinos are efficiently produced non-thermally and the observed baryon asymmetry can be explained even for a reheating temperature respecting the gravitino bound if two conditions are satisfied: the initial value of the flat direction must be close to Planckian values and the phase-dependent terms in the flat direction potential are either vanishing or sufficiently small. We then show that flat directions also contribute to the total curvature perturbation. Such perturbation is generated at the first oscillation of the flat direction condensate when the latter relaxes to the minimum of its potential after the end of inflation. If the contribution to the total curvature perturbation from supersymmetric flat direction is the dominant one, then a significant level of non-Gaussianity in the cosmological perturbation is also naturally expected. Finally, we argue that supersymmetric flat direction VEVs can decay non perturbatively via preheating even in the case where they undergo elliptic motion in the complex plane instead of radial motion through the origin. It has been generally argued that in this case adiabaticity is never violated and preheating is inefficient. Considering a toy U(1) gauge theory, we explicitly calculate the scalar potential, in the unitary gauge, for excitations around several flat directions. We show that the mass matrix for the excitations has non-diagonal entries which vary with the phase of the flat direction vacuum expectation value. Furthermore, this mass matrix has zero eigenvalues whose eigenstates change with time. We show that these light degrees of freedom are produced copiously in the non-perturbative decay of the flat direction VEV.
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Darmé, Luc. "Unconventional particle behaviours in supersymmetric theories and gravity." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066161/document.
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Nous étudions dans un premier temps deux théories supersymétriques basées sur la présence de Gauginos de Dirac à travers deux scénarios à la phénoménologie bien distincte. La première, dite de "Fake Split SUSY", se caractérise par un spectre de particules scindé entre une partie à l'échelle électrofaible et l'autre plus lourde. Ces modèles prédisent avec une grande précision la masse du boson de Higgs et sont compatibles avec de nombreux résultats de cosmologie, au prix d'un spectre très peu naturel. La seconde présente un scénario supersymétrique dont l'un des bosons scalaire pourrait être identifié avec la résonance à 750 GeV observée au LHC. Dans un second temps, nous analysons deux comportements non-conventionnels du graviton et de son partenaire supersymétrique, le gravitino. Lorsque la symétrie de Lorentz est brisée par la présence d'un fluide, nous montrons que la pseudo-particule générée par cette brisure, le phonino, devient la composante longitudinale du gravitino et se propage suivant une relation de dispersion non relativiste que nous étudions en détails. Finalement, nous explorons des théories de gravité étendue dans lesquelles, en sus du Lagrangien d'Hilbert-Einstein, nous ajoutons des opérateurs construits à partir de produits de tenseurs de Riemann. En présence d'un fluide, nous prouvons qu'un graviton peut se propager "prestement", une notion reliée celle de vitesse superluminale<br>We will first focus on supersymmetric theories with Dirac Gaugino masses. We investigate two advantages of such models. First, the possibility to reconcile the measured Higgs mass with an arbitrary large scale of supersymmetry breaking. Second, we show how the scalar singlet present in such models is a sound candidate for a resonance explaining the 750 GeV diphoton excess observed by the LHC experiments. In a second part, we start by discussing the propagation of a massive spin 3/2 state in a fluid (for instance the gravitino when supergravity is coupled to a background fluid). We show that the degrees of freedom corresponding to different helicities travel with different velocities. We then discuss the separate issue of graviton speed in extended gravity theories where the usual Einstein-Hilbert Lagrangian is supplemented by various higher order terms constructed from Riemann tensors
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Patrick, Richard J. II. "The search for supersymmetry in particle physics." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527406.
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<p> Experimental high energy physics (HEP) techniques are applied to accurate simulated collider data in search for existence or exclusion of supersymmetric (SUSY) particles. Supersymmetry is a leading candidate to resolve the hierarchy problem in particle physics as well as offer a stable dark matter candidate. Techniques and practices are explored and applied to the leptonic decay process production followed by and where is the proton, is the chargino, , are neutralinos and , are the standard model W and Higgs Bosons respectively. Signal yields are in general agreement with other researchers and ranged from 0.5 to 62.6 events. Reduction in the background to signal ratio is demonstrated through isolating the SUSY process and applying theoretical knowledge of the signal and associated dominant backgrounds. Results from this study establish procedures for future work with actual data, offer a benchmark for this specific leptonic decay process and may motivate variable selection and cut criteria choices in future analysis of similar signal processes.</p>
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Hardy, Edward. "Supersymmetry and electroweak fine tuning." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:832194dd-c075-4f18-bc88-3822fa745aea.
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Low scale supersymmetry (SUSY) is a compelling solution to the electroweak hierarchy problem. However, increasingly strong limits on the masses of superpartners, first from LEP and now the LHC, mean that the simplest models require significant fine tuning. This thesis is dedicated to the study of a possible alternative low energy superpartner spectrum, natural SUSY, in which only superparticles directly involved in stabilising the electroweak scale are light, alleviating collider limits and potentially reducing tuning. After reviewing how low scale SUSY is motivated by the hierarchy problem, we build a model of SUSY breaking and mediation that successfully generates a natural SUSY spectrum. This also suppresses the first two generation fermion Yukawas, and leads to small parameters in the hidden sector, which are required for successful SUSY breaking. A challenge in models of natural SUSY is raising the physical Higgs mass to 125 GeV, and we study the possibility that this could occur through the addition of a singlet to the theory. If stops are very light, the coupling of the singlet to the Higgs needs to be so large that it becomes nonperturbative before the scale of grand unification, raising the concern that precision gauge coupling unification may be upset. However, we find that this is not necessarily the case. Rather it is possible this could correct for the present ∽ 3% discrepancy in the two-loop minimal supersymmetric model's unification prediction. We then turn to the fine tuning in models of natural SUSY, emphasising that this should be measured with respect to the theory's ultraviolet (UV) parameters. We show that the first two generation sfermions can be made relatively heavy, beyond LHC reach, without introducing tuning. However, the gluino generates a significant tuning through the stops during the renormalisation group flow. As a result, there is no fine tuning benefit in reducing the stop masses below (50 - 75)% of the weak scale gluino mass, and we obtain strong lower bounds on the tuning of theories compatible with collider limits. We also study theories with Dirac gauginos, which have relatively low fine tuning even if the scale of mediation is high. Finally, we consider the effect of relaxing a common assumption and allowing the hidden SUSY breaking sector to modify the running of the visible sector soft masses. This may plausibly occur in realistic models and could dramatically reduce the fine tuning of SUSY theories.
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Kaplan, David Elazzar. "Flavor mediated supersymmetry breaking /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9729.
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