614 research outputs found
Entrepreneurial marketing in subsistence marketplaces
No full textThere are more than a billion poverty-stricken entrepreneurs in the world who run micro-enterprises to meet basic consumption needs. This pervasive phenomenon presents an interesting theoretical conundrum - that of consumer-entrepreneur duality. This duality blurs the boundaries between consumption and entrepreneurship, which have traditionally been distinct domains of scholarly inquiry. The research reported in this dissertation aims to a) provide a theoretical foundation for the notion of consumer-entrepreneur duality and b) test the implications of the aforementioned duality empirically. A key insight flowing from the investigations is that factors in the consumption domain impact important outcomes in the entrepreneurial domain and vice versa.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Srinivas Venugopal, accepted the attached license on 2016-04-18 at 08:47.The student, Srinivas Venugopal, submitted this Dissertation for approval on 2016-04-18 at 09:04.This Dissertation was approved for publication on 2016-04-19 at 08:14.DSpace SAF Submission Ingestion Package generated from Vireo submission #9286 on 2016-07-07 at 14:17:05Made available in DSpace on 2016-07-07T21:17:37Z (GMT). No. of bitstreams: 4
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Previous issue date: 2016-04-19Embargo set by: Seth Robbins for item 93274
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Recherche d'un boson de higgs doublement chargé se désintégrant en deux bosons W de même signe dans l’extension triplet-doublet du modèle standard avec le détecteur Atlas au LHC
No full textLa recherche de bosons scalaires de charge électrique +2 se désintégrant en deux bosons W de même charge est effectuée en analysant un échantillon de données collectées en 2015 et 2016 à une énergie de centre de masse de 13 Tev au LHC auprès du détecteur ATLAS, correspondant à une luminosité intégrée de 36.1 fb⁻¹. Cette recherche est motivée par un modèle comprenant une extension du secteur scalaire grâce à l'ajout d'un triplet. Il propose une explication à la masse des neutrinos et prédit une riche phénoménologie autour des bosons scalaires de charge +1 et +2 ainsi que des deux nouveaux bosons neutres, en plus d'un aux propriétés identiques à celles du boson de Higgs du MS. Le boson doublement chargé est produit par paires dans les collisions proton-proton et se désintègre majoritairement en bosons W. L'intervalle de masse exploré est situé entre 200 et 700 GeV, en utilisant des signatures expérimentales qui incluent plusieurs leptons, de l'énergie transverse manquante et des jets. L'analyse avec trois leptons dans l'état final est décrite dans cette thèse. Une combinaison de l'analyse avec deux, trois et quatre leptons est réalisée pour augmenter la sensibilité. Une interprétation statistique des résultats donne une limite inférieure en masse de 220 GeV. Ceci constitue la première recherche expérimentale de ce modèle dans cet espace de paramètres auprès d'un collisionneur.A search for doubly charged scalar bosons decaying to W boson pairs is performed using a data sample corresponding to an integrated luminosity of 36.1 fb⁻¹ collected by the ATLAS detector at the LHC at a centre-of-mass energy of 13 TeV in 2015 and 2016. The search is guided by a model including an extension of the scalar sector through a scalar triplet which provides an explanation of neutrino masses. Such a model predicts a rich phenomenology that includes singly- and doubly-charged bosons, and two new neutral bosons, besides a boson whose properties are identical to the SM Higgs boson. The doubly-charged bosons are produced by pairs in proton-proton collisions and decay predominantly into W bosons. The mass range from 200 to 700 GeV is explored using experimental signatures including several leptons, missing transverse energy and jets. The analysis in the final state of three leptons is described in this thesis. A combination of the analysis in two, three, and four leptons is used to enhance sensitivity. A statistical interpretation of the results gives an observed lower bound on the mass of 220 GeV. This is the first search of this model in this parameter space at the colliders
High-mass resonances decaying to heavy particles with ATLAS
No full textThe unprecedented LHC dataset is being explored looking for massive particles decaying in a plethora of ways. We give the latest results from ATLAS on searches for new heavy particles decaying to known particles, X->ttbar, tb, bb, VV, VH, HH, Hgamma, tautau, and on searches involving a decay to potential unknown ones, X->ZH' and X->AB. All these analyses use the full run 2 dataset
Search for a doubly charged Higgs boson decaying to same-sign W bosons in a triplet-doublet extension of the Standard Model with the ATLAS detector at the LHC
No full textLe secteur scalaire du Modèle Standard (MS) est l’un des meilleurs candidats pour contenir les nouvelles particules au-delà du Modèle Standard. Les mesures de précision des propriétés du boson de Higgs ainsi que la recherche de nouveaux scalaires est d’une ultime importance. L’ajout d’un triplet de scalaires aux champs du MS dans le contexte des modèles dits "Type 2 Seesaw" explique pourquoi les neutrinos sont massifs tout en prédisant de nouveaux scalaires, parmi lesquels certains ont une masse à l’échelle électrofaible, et donc, seraient détectables au LHC. La montée en énergie et en luminosité du Run 2 du LHC augmente significativement le potentiel de découverte de cette extension du secteur scalaire. Une variante d’une telle extension est explorée dans cette thèse : le triplet scalaire, ∆, est doté d’une hypercharge Y = 2, en complément du doublet scalaire H du MS. Ce secteur scalaire mixte en- tre doublet et triplet est dirigé par 6 couplages, définissant les multiples interactions entre les champs scalaires respectifs. Les composantes neutres du doublet et du triplet prennent une valeur vd et vt (la VEV, ou valeur attendue dans le vide) au minimum du potentiel, causant par la même la brisure de symétrie électrofaible. En particulier, la vev du triplet est contrainte par les mesures de précisions électrofaibles et doit se situer sous l’échelle du GeV. La brisure de symétrie produit une phénoménolo- gie riche, incluant sept scalaires, dont un peut être identifié au boson de Higgs du MS : H±± et H± des bosons de Higgs simplement ou doublement chargés, A0 un boson de Higgs neutre CP odd et deux autre CP even h0 et H0. La recherche de bosons de Higgs doublement chargés a déjà été réalisée au LHC en utilisant des états finaux plus inclusifs, à savoir le canal dileptonique. Ces analyses ont été ré-interprétées dans le cas où la désintégration en deux bosons est favorisée, affaiblissant ces limites. Il est donc nécessaire de réaliser une analyse dédiée qui exploite la totalité des capacités expérimentales pour explorer ce modèle, notemment en prenant en compte la présence d’énergie transverse manquante et de multi-jets issus de l’état final multibosonique dans l’optimisation de la sélection. Cette thèse se focalise sur la phénoménologie des bosons scalaires doublement chargés H±±, dans le cas où le couplage aux leptons est défavorisé au profit des bosons vecteurs du MS, c’est à dire dans le canal de désintégration H±± → W ±W ±. Les bosons de Higgs doublement chargés peuvent être produits par paires, ce qui est caractérisé par un état final à quatre bosons W . La recherche de ces particules est réalisée pour six masses du H±± : 200, 300, 400, 500, 600, and 700 GeV. Cette étude est possible dans différents états finaux, comme l’état final à deux leptons de même signe, à trois leptons et quatre leptons. La signature expérimentale étudiée dans cette thèse concerne l’état final avec trois leptons, de l’énergie transverse manquante et deux jets. Les bruits de fond dominants proviennent de processus du MS tels que WZ, ZZ, Z+jets et tt¯. Les bruits de fonds primaires (ou "prompts") sont estimés à l’aide de simulations Monte Carlo. Mais dans le cas où un jet passe pour un lepton ou si l’origine d’un lepton est une désintégration secondaire (ou "non-prompte"), comme pour les désintégrations semi-leptoniques des b, les simulations ne sont pas suffisantes et il est nécessaire, pour ces bruits, d’utiliser des méthodes d’extraction depuis les données, notemment la méthode dite des "fake factor". Celle-ci n’utilise que les données et les simulations de processus primaires qui sont correctement décrits. Lorsque le bruit de fond est bien décrit, un ensemble de coupures de sélection est appliqué pour supprimer une fraction significative de processus caractéristiques
VLQ searches and hadronic final states in the ATLAS experiment
No full textSeveral models which go beyond the Standard Model (BSM) predict the existence of Vector-like quarks (VLQs). One such class of models, known as Composite Higgs Models (CHMs), attempts to reduce the fine-tuning of the mass of the Higgs boson. This document presents a selection of searches for such VLQs in the context of minimal CHMs, in final states with jets. No significant excesses were seen. However, the current lower bounds on the mass of different types of vector-like quarks which may arise as a singlet or as a part of a doublet extend upto about 2 TeV
Exotic Decays of Vector-Like Quarks and Development of a Test Procedure for the ITk Strip Module at the ATLAS Detector for the HL-LHC
No full textThe naturalness problem of the Standard Model (SM) challenges our understanding of the origin of mass. Several theories have been proposed to tackle the problem, one of them is the Composite Higgs Model (CHM) where the Higgs boson of the SM is not an elementary scalar but instead a composite object bound at a confinement scale of a TeV. The fine-tuning of the Higgs boson mass, arising from the naturalenss problem, is thus reduced by the lower cut-off scale of the SM and an overall symmetry protection in the theory. Consequences of the CHM are new states, both fermions, so called Vector-Like Quarks (VLQ), and scalars with masses low enough to be produced at the LHC. In ATLAS, existing searches for VLQs assume decays into known SM particles. In this thesis, a phenomenological study is presented where the VLQ decays to a Beyond the Standard Model (BSM) scalar or pseduoscalar, quantifying the sensitivity of the current experiments at the LHC to the such decays. The reach is well above 1 TeV in VLQ mass thus directly competing with VLQ decay to known SM states. The phenomenological study is continued with the ATLAS experiment where the VLQ decays into a BSM scalar with a diphoton final state. The data-driven background modeling is covered and expected limits are presented showing good sensitivity to exotic decays of VLQ. The LHC is reaching its limit in energy and luminosity. The next step is an upgrade to the High-Luminosity LHC (HL-LHC), significantly raising the data rates. For the ATLAS experiment to cope with the data rates delivered by the HL-LHC, the detector needs to the upgraded. In this thesis, a detailed description of a test procedure for a trigger and readout scheme for the new inner tracker strip detector modules is presented
Aggregate breakdown of nanoparticulate titania
No full textSix nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales.
Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime.
A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from compaction via dry pressing and tape casting secondary scale aggregates. Mercury porosimetry of tapes cast at 0.85 and 9.09 cm/sec exhibited pore sizes ranging from 200-500 nm suggesting packing of intact micron-sized primary aggregates. Porosimetry further showed that this peak was absent in pressed pellets corroborating arguments of ruptured primary aggregates during compaction to 750 MPa.Ph.D.Includes bibliographical references (p. 166-170)
Parallelizing Unstructured Sparse Matrix Computations on Large-Scale Multiprocessors
No full textProblems in the class of unstructured sparse matrix computations are characterized by highly irregular dependencies and communication patterns that are not known at compile-time, but can be completely determined at run-time before the computations are actually performed. For this class of problems, current parallelizing compilers are unable to produce efficient code on large-scale distributed memory MIMD multiprocessors, and manual techniques are inflexible and too ad hoc to be generally effective.
In this thesis, we propose a run-time automatic partitioning and scheduling methodology for unstructured sparse matrix computations on large-scale multiprocessors. Our methodology is based on extracting information from the problem instance by preprocessing its symbolic structure, and using this information to achieve high performance in repeated iterations of the computations during which the symbolic structure is unchanged. We present efficient software tools to help users build their parallelization system by following this methodology.
We demonstrate the efficacy of our methodology on sparse Cholesky factorization, which has historically proven to be hard to parallelize. The highlight of our approach is a new two-dimensional block partitioning scheme. We build a run-time parallel system for block sparse Cholesky factorization called Sparse Hybrid Automatic Parallelization Environment (SHAPE), consisting of a parallel partitioner, a parallel scheduler and a parallel communication optimization algorithm. These are modular tools tied together by an explicit representation for block-based unstructured computations. We employ SHAPE to carry out an extensive experimental study of sparse Cholesky factorization on the iPSC/860. The experimental results show that with a judicious choice of partitioning parameters, our block-based partitioning and scheduling method outperforms a well-known column-based method in delivering high performance on a variety of structured and unstructured matrices. The preprocessing itself is shown to be very efficient, its cost being recovered in a small number of iterations of the factorization.
Our methodology and tools may be used to parallelize other unstructured sparse matrix computations for which the same symbolic structure is used in several iterations of the computations. Such computations include sparse triangular solution and sparse
matrix-vector multiplication.Technical report DCS-TR-30
Heavy vector-like quarks decaying to exotic scalars: a case study with triplets
No full textWe investigate the pair production of a vector-like quark triplet with hypercharge 5/3 decaying into top quark and a complex scalar triplet with hypercharge 1 at the LHC. This novel scenario, featuring particles with exotic charges - two quarks with charge 8/3 and 5/3 and a scalar with charge 2 - serves as a unique window to models based on the framework of partial compositeness, where these particles naturally emerge as bound states around the TeV scale. Leveraging on the LHC data we establish exclusion limits on the masses of the vector-like quark and the scalar triplet. Subsequently, we design an analysis strategy aimed at improving sensitivity in the region which is still allowed. Our analysis focuses on two specific regions in the parameter space: the first entails a large mass gap between the vector-like quarks and the scalars, so that the vector-like quarks can decay into the scalars; the second involves a small mass gap, such that this decay is forbidden. To simplify the parameter space, both vector-like quarks and scalars are assumed to be degenerate or almost degenerate within the triplets, such that chain decays between fermions and scalars are suppressed. As a result, we found that final states characterized by a same-sign lepton pair, multiple jets, and high net transverse momentum (i.e. effective mass) will play a pivotal role to unveil this model and, more in general, models characterised by multiple vector-like quarks around the same mass scale during the high luminosity LHC phase.22 pages, 10 figures, 8 tables. Simulation banners are attached as ancillary files, v2: references updated, matches JHEP versio
SHAPE: A Parallelization Tool for Sparse Matrix Computations
No full textWe describe the design, implementation and performance of a Sparse Hybrid Automatic Parallelization Environment (SHAPE). SHAPE partitions and schedules sparse matrix computations for Cholesky factorization with the goal of achieving good performance at low cost, while providing flexibility for use as an experimental tool. It employs efficient parallelization algorithms which reduce the communication cost without adversely affecting the load balance by using a hybrid mixture of column and block partitions. Through several parameters, SHAPE aims for portability across a diverse range of sparse matrix structures and message-passing multiprocessors with different communication cost parameters. We present preliminary timing results on the iPSC/860 and compare the performance of SHAPE with that of a commonly used column-based method. The results show that SHAPE significantly reduces computation time, number of messages, and overall communication time for a variety of test matrices.Technical report dcs-tr-29
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