Search for supersymmetry in final states with jets, missing transverse energy and one charged lepton with the ATLAS-experiment

Im Jahr 2011 wurde am Large Hadron Collider mit dem ATLAS Experiment ein Datensatz von 4.7 inversen Femtobarn bei einer Schwerpunktsenergie von 7 TeV aufgezeichnet. Teil des umfangreichen Physikprogrammes des ATLAS Experiments ist die Suche nach Physik jenseits des Standardmodells. Supersymmetrie - eine neue Symmetrie zwischen Bosonen und Fermionen - wird als aussichtsreichester Kandidat für neue Physik angesehen, und zahlreiche direkte und indirekte Suchen nach Supersymmetrie wurden in den letzten Jahrzehnten bereits durchgeführt. In der folgenden Arbeit wird eine direkte Suche nach Supersymmetrie in Endzuständen mit Jets, fehlender Transversalenergie und genau einem Elektron oder Myon durchgeführt. Der analysierte Datensatz von 4.7 inversen Femtobarn umfasst die gesamte Datenmenge, welche am ATLAS Experiment bei einer Schwerpunktsenergie von 7 TeV aufgezeichnet wurde. Die Ergebnisse der Analyse werden mit verschiedenen anderen leptonischen Suchkanälen kombiniert, um die Sensitivität auf diversen supersymmetrischen Produktions- und Zerfallsmodi zu maximieren. Die gemessenen Daten sind kompatibel mit der Standardmodellerwartung, und neue Ausschlussgrenzen in verschiedenen supersymmetrischen Modellen werden berechnet.

Variazioni di gravità generate da processi deformativi in un semispazio elastico

La precisione delle misure dell’accelerazione di gravità effettuate grazie ai gravimetri più moderni fornisce importanti informazioni relative ai processi deformativi, che avvengono nel nostro pianeta. In questa tesi il primo capitolo illustra alcuni fondamenti della teoria dell’elasticità ed in particolare la possibilità di descrivere qualunque sorgente deformativa interna alla Terra tramite una distribuzione di “forze equivalenti” con risultante e momento nulli. Inoltre descriviamo i diversi contributi alle variazioni di gravità prodotte da tali eventi. Il secondo capitolo fornisce alcune tecniche di soluzione dell’equazione di Laplace, utilizzate in alcuni calcoli successivi. Nel terzo capitolo si sviluppano le soluzioni trovate da Mindlin nel 1936, che analizzò spostamenti e deformazioni generate da una forza singola in un semispazio elastico omogeneo con superficie libera. Si sono effettuati i calcoli necessari per passare da una forza singola a un dipolo di forze e una volta trovate queste soluzioni si sono effettuate combinazioni di dipoli al fine di ottenere sorgenti deformative fisicamente plausibili, come una sorgente isotropa o una dislocazione tensile (orizzontale o verticale), che permettano di descrivere fenomeni reali. Nel quarto capitolo si descrivono i diversi tipi di gravimetri, assoluti e relativi, e se ne spiega il funzionamento. Questi strumenti di misura sono infatti utilizzati in due esempi che vengono descritti in seguito. Infine, nel quinto capitolo si sono applicati i risultati ottenuti nel terzo capitolo al fine di descrivere i fenomeni avvenuti ai Campi Flegrei negli anni ‘80, cercando il tipo di processo deformativo più adatto alla descrizione sia della fase di sollevamento del suolo che quella di abbassamento. Confrontando le deformazioni e le variazioni residue di gravità misurate prima e dopo gli eventi deformativi con le previsioni dei modelli si possono estrarre importanti informazioni sui processi in atto.

Metodi numerici di regolarizzazione per l'inversione 2d di dati di risonanza magnetica nucleare

Molte applicazioni sono legate a tecniche di rilassometria e risonanza magnetica nucleare (NMR). Tali applicazioni danno luogo a problemi di inversione della trasformata di Laplace discreta che è un problema notoriamente mal posto. UPEN (Uniform Penalty) è un metodo numerico di regolarizzazione utile a risolvere problemi di questo tipo. UPEN riformula l’inversione della trasformata di Laplace come un problema di minimo vincolato in cui la funzione obiettivo contiene il fit di dati e una componente di penalizzazione locale, che varia a seconda della soluzione stessa. Nella moderna spettroscopia NMR si studiano le correlazioni multidimensionali dei parametri di rilassamento longitudinale e trasversale. Per studiare i problemi derivanti dall’analisi di campioni multicomponenti è sorta la necessità di estendere gli algoritmi che implementano la trasformata inversa di Laplace in una dimensione al caso bidimensionale. In questa tesi si propone una possibile estensione dell'algoritmo UPEN dal caso monodimensionale al caso bidimensionale e si fornisce un'analisi numerica di tale estensione su dati simulati e su dati reali.

Devising: Pioneering Uncharted Territory in Theater

Throughout theatre history, styles of theatre have come in and out of favor in response to the zeitgeist of the period. Neoclassical, Melodrama, Naturalism, all have their place in history offering enlightenment, passion and truth each in tune with the values of the culture in which it was created. As society transforms, so too does the stage, offering new ways to reflect, interpret and challenge our assumptions about the changing world. Our current society wrestles with a ‘shrinking world’, a world consumed with technological advances that fan the fire of the growing interconnectedness of human beings all over the earth. This ‘shrinking world’ phenomenon has the effect of an‘expanded world awareness’. That is to say, now more than ever we question all assumption regarding singular perspectives and cultural convictions. What our new society values is diversification of insight and a myriad of experiences from which to draw our conclusions about the world in which we live. The kind of theatre that fills this need is Devised Theatre. Theatre is a collaborative art form by nature. Theatre cannot be practiced alone. One must partner other artists as well as an audience in order to create a theatre performance. Theatre is a dialogue which can take many shapes. Devised Theatre is a process of making theatre that enables a group of performers to be physically and practically creative in the sharing and shaping of an original product that directly emanates from assembling, editing and reshaping individual’s contradictory experiences of the world. A devised theatre product is a work that has emerged from and been generated by a group of people working in collaboration. There is an emphasis on a way of working that values an accumulation of ideas. (Oddey)

Equivariant inverse spectral theory and toric orbifolds

Let O-2n be a symplectic toric orbifold with a fixed T-n-action and with a tonic Kahler metric g. In [10] we explored whether, when O is a manifold, the equivariant spectrum of the Laplace Delta(g) operator on C-infinity(O) determines O up to symplectomorphism. In the setting of tonic orbifolds we shmilicantly improve upon our previous results and show that a generic tone orbifold is determined by its equivariant spectrum, up to two possibilities. This involves developing the asymptotic expansion of the heat trace on an orbifold in the presence of an isometry. We also show that the equivariant spectrum determines whether the toric Kahler metric has constant scalar curvature. (C) 2012 Elsevier Inc. All rights reserved.

The discrete Pascal transform and its applications

We introduce a new discrete polynomial transform constructed from the rows of Pascal’s triangle. The forward and inverse transforms are computed the same way in both the oneand two-dimensional cases, and the transform matrix can be factored into binary matrices for efficient hardware implementation. We conclude by discussing applications of the transform in

Hearing Delzant Polytopes From the Equivariant Spectrum

Let M^{2n} be a symplectic toric manifold with a fixed T^n-action and with a toric K\"ahler metric g. Abreu asked whether the spectrum of the Laplace operator $\Delta_g$ on $\mathcal{C}^\infty(M)$ determines the moment polytope of M, and hence by Delzant's theorem determines M up to symplectomorphism. We report on some progress made on an equivariant version of this conjecture. If the moment polygon of M^4 is generic and does not have too many pairs of parallel sides, the so-called equivariant spectrum of M and the spectrum of its associated real manifold M_R determine its polygon, up to translation and a small number of choices. For M of arbitrary even dimension and with integer cohomology class, the equivariant spectrum of the Laplacian acting on sections of a naturally associated line bundle determines the moment polytope of M.

Isospectrality and Heat Content

We present examples of isospectral operators that do not have the same heat content. Several of these examples are planar polygons that are isospectral for the Laplace operator with Dirichlet boundary conditions. These include examples with infinitely many components. Other planar examples have mixed Dirichlet and Neumann boundary conditions. We also consider Schrodinger operators acting in L-2[0,1] with Dirichlet boundary conditions, and show that an abundance of isospectral deformations do not preserve the heat content.

Whither PQL?

Generalized linear mixed models (GLMM) are generalized linear models with normally distributed random effects in the linear predictor. Penalized quasi-likelihood (PQL), an approximate method of inference in GLMMs, involves repeated fitting of linear mixed models with “working” dependent variables and iterative weights that depend on parameter estimates from the previous cycle of iteration. The generality of PQL, and its implementation in commercially available software, has encouraged the application of GLMMs in many scientific fields. Caution is needed, however, since PQL may sometimes yield badly biased estimates of variance components, especially with binary outcomes. Recent developments in numerical integration, including adaptive Gaussian quadrature, higher order Laplace expansions, stochastic integration and Markov chain Monte Carlo (MCMC) algorithms, provide attractive alternatives to PQL for approximate likelihood inference in GLMMs. Analyses of some well known datasets, and simulations based on these analyses, suggest that PQL still performs remarkably well in comparison with more elaborate procedures in many practical situations. Adaptive Gaussian quadrature is a viable alternative for nested designs where the numerical integration is limited to a small number of dimensions. Higher order Laplace approximations hold the promise of accurate inference more generally. MCMC is likely the method of choice for the most complex problems that involve high dimensional integrals.

Posterior Simulation in the Generalized Linear Model with Semiparmetric Random Effects

Generalized linear mixed models with semiparametric random effects are useful in a wide variety of Bayesian applications. When the random effects arise from a mixture of Dirichlet process (MDP) model, normal base measures and Gibbs sampling procedures based on the Pólya urn scheme are often used to simulate posterior draws. These algorithms are applicable in the conjugate case when (for a normal base measure) the likelihood is normal. In the non-conjugate case, the algorithms proposed by MacEachern and Müller (1998) and Neal (2000) are often applied to generate posterior samples. Some common problems associated with simulation algorithms for non-conjugate MDP models include convergence and mixing difficulties. This paper proposes an algorithm based on the Pólya urn scheme that extends the Gibbs sampling algorithms to non-conjugate models with normal base measures and exponential family likelihoods. The algorithm proceeds by making Laplace approximations to the likelihood function, thereby reducing the procedure to that of conjugate normal MDP models. To ensure the validity of the stationary distribution in the non-conjugate case, the proposals are accepted or rejected by a Metropolis-Hastings step. In the special case where the data are normally distributed, the algorithm is identical to the Gibbs sampler.

FAST ADAPTIVE PENALIZED SPLINES

This paper proposes a numerically simple routine for locally adaptive smoothing. The locally heterogeneous regression function is modelled as a penalized spline with a smoothly varying smoothing parameter modelled as another penalized spline. This is being formulated as hierarchical mixed model, with spline coe±cients following a normal distribution, which by itself has a smooth structure over the variances. The modelling exercise is in line with Baladandayuthapani, Mallick & Carroll (2005) or Crainiceanu, Ruppert & Carroll (2006). But in contrast to these papers Laplace's method is used for estimation based on the marginal likelihood. This is numerically simple and fast and provides satisfactory results quickly. We also extend the idea to spatial smoothing and smoothing in the presence of non normal response.

Stochastic rank correlation: a robust merit function for 2D/3D registration of image data obtained at different energies

In this article, the authors evaluate a merit function for 2D/3D registration called stochastic rank correlation (SRC). SRC is characterized by the fact that differences in image intensity do not influence the registration result; it therefore combines the numerical advantages of cross correlation (CC)-type merit functions with the flexibility of mutual-information-type merit functions. The basic idea is that registration is achieved on a random subset of the image, which allows for an efficient computation of Spearman's rank correlation coefficient. This measure is, by nature, invariant to monotonic intensity transforms in the images under comparison, which renders it an ideal solution for intramodal images acquired at different energy levels as encountered in intrafractional kV imaging in image-guided radiotherapy. Initial evaluation was undertaken using a 2D/3D registration reference image dataset of a cadaver spine. Even with no radiometric calibration, SRC shows a significant improvement in robustness and stability compared to CC. Pattern intensity, another merit function that was evaluated for comparison, gave rather poor results due to its limited convergence range. The time required for SRC with 5% image content compares well to the other merit functions; increasing the image content does not significantly influence the algorithm accuracy. The authors conclude that SRC is a promising measure for 2D/3D registration in IGRT and image-guided therapy in general.

Educational and Anthropological Perspectives: An Italian View on Migration in Multi-cultural Urban Spaces

In contemporary societies there are different ways to perceive the relation between identity and alterity and to describe the difference between “us” and “them”, residents and foreigners. Anthropologist Sandra Wallman sustains that in multi-cultural urban spaces the frontiers of diversity are not only burdensome markers of identity, but rather they could also represent new chances to define “identity” and “alterity”. These frontiers, in fact, can work like interfaces through which to build time after time, in a creative way, a relationship with the other. From this point of view, the concept of boundary can offer many opportunities to creatively define the relation with the other and to sign new options for cognitive and physical movement. On the other side, in many cases we have a plenty of mechanisms of exclusion that transforms a purely empirical distinction between “us” and “them” in an ontological contrast, as in the case when the immigrant undergoes hostilities through discriminatory language. Even though these forms of racism are undoubtedly objectionable from a theoretical point of view, they are anyway socially “real”, in the sense that they are perpetually reaffirmed and strengthened in public opinion. They are in fact implicit “truths”, realities that are considered objective, common opinions that are part of day-to-day existence. That is the reason why an anthropological prospective including the study of “common sense” should be adopted in our present day studies on migration, as pointed out by American anthropologist Michael Herzfeld. My primary goal is to analyze with such a critical approach same pre-conditions of racism and exclusion in contemporary multi-cultural urban spaces. On the other hand, this essay would also investigate positive strategies of comparing, interchanging, and negotiating alterity in social work. I suggest that this approach can offer positive solutions in coping with “diversity” and in working out policies for recognizing a common identity which, at the same time, do not throw away the relevance of political and economic power.

Visual Fixation for 3D Video Stabilization

Visual fixation is employed by humans and some animals to keep a specific 3D location at the center of the visual gaze. Inspired by this phenomenon in nature, this paper explores the idea to transfer this mechanism to the context of video stabilization for a handheld video camera. A novel approach is presented that stabilizes a video by fixating on automatically extracted 3D target points. This approach is different from existing automatic solutions that stabilize the video by smoothing. To determine the 3D target points, the recorded scene is analyzed with a stateof- the-art structure-from-motion algorithm, which estimates camera motion and reconstructs a 3D point cloud of the static scene objects. Special algorithms are presented that search either virtual or real 3D target points, which back-project close to the center of the image for as long a period of time as possible. The stabilization algorithm then transforms the original images of the sequence so that these 3D target points are kept exactly in the center of the image, which, in case of real 3D target points, produces a perfectly stable result at the image center. Furthermore, different methods of additional user interaction are investigated. It is shown that the stabilization process can easily be controlled and that it can be combined with state-of-theart tracking techniques in order to obtain a powerful image stabilization tool. The approach is evaluated on a variety of videos taken with a hand-held camera in natural scenes.