Studio di metodi di ricostruzione di top molto energetici all'esperimento atlas

L’acceleratore di protoni e ioni pesanti LHC costruito presso i laboratori del CERN di Ginevra permette sviluppi straordinari nel campo della fisica delle particelle alle alte energie. Tra le diverse linee di ricerca attualmente operative lo studio del quark top riveste un ruolo di particolare rilevanza. Infatti, l’elevata energia accessibile alla macchina rende possibile la raccolta di campioni di elevata statistica necessari per uno studio dettagliato delle proprietà del quark top, la particella più pesante fino ad oggi nota. In particolare in questa tesi viene studiato, e confrontato con l'analisi standard, un nuovo metodo, chiamato “template overlap method”, per la selezione di quark top prodotti ad alta energia. L'obiettivo è valutare se questo nuovo metodo permetterà una migliore precisione nella misura della sezione d'urto differenziale di produzione di coppie tt nelle prossime prese dati dove l'energia nel centro di massa raggiungerà i 13 TeV. L'analisi, per ora, è stata svolta su dati montecarlo simulati per l'esperimento ATLAS ad una energia del centro di massa di 8 TeV. I risultati ottenuti sono incoraggianti perchè mostrano un'alta efficienza di selezione all'aumentare dell'energia dei prodotti di decadimento del top.

Study of a new method for high energy top tagging at the ATLAS experiment

Since its discovery, top quark has represented one of the most investigated field in particle physics. The aim of this thesis is the reconstruction of hadronic top with high transverse momentum (boosted) with the Template Overlap Method (TOM). Because of the high energy, the decay products of boosted tops are partially or totally overlapped and thus they are contained in a single large radius jet (fat-jet). TOM compares the internal energy distributions of the candidate fat-jet to a sample of tops obtained by a MC simulation (template). The algorithm is based on the definition of an overlap function, which quantifies the level of agreement between the fat-jet and the template, allowing an efficient discrimination of signal from the background contributions. A working point has been decided in order to obtain a signal efficiency close to 90% and a corresponding background rejection at 70%. TOM performances have been tested on MC samples in the muon channel and compared with the previous methods present in literature. All the methods will be merged in a multivariate analysis to give a global top tagging which will be included in ttbar production differential cross section performed on the data acquired in 2012 at sqrt(s)=8 TeV in high phase space region, where new physics processes could be possible. Due to its peculiarity to increase the pT, the Template Overlap Method will play a crucial role in the next data taking at sqrt(s)=13 TeV, where the almost totality of the tops will be produced at high energy, making the standard reconstruction methods inefficient.

Control over the hydrophobic behavior of polystyrene surface by annealing temperature based on capillary template wetting method

The wetting behavior of water droplets was studied on tunable nanostructured polystyrene (PS) surfaces fabricated by temperature-induced capillary template wetting. The surface morphology of PS varied with the annealing temperature. Contact angle (CA) measurements showed that the wettability of polystyrene surfaces could be tuned from hydrophobic (CA = 104°) to superhydrophobic (CA = 161°) by rendering different morphologies, which could be explained by two distinct wetting modes, i.e., the Wenzel and Cassie–Baxter wetting state. Meanwhile, the critical annealing temperature inducing wetting transition between the Wenzel state and Cassie–Baxter state was obtained. This approach could be easily extended to produce superhydrophobic surfaces on other thermoplastic polymers.

LaNiO3 nanotubes produced using a template-assisted method

We have studied the experimental conditions needed to produce LaNiO3 (LNO) nanostructures using a template-assisted method. In this route, a mesoporous anodic aluminum oxide template was filled with a chemical solution that had been prepared with polymeric precursors route. The precursor solutions and synthesized samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis, infrared spectroscopy and high-resolution scanning electron microscopy (HRSEM). The XRD results for the samples that were heat-treated at 700 degrees C revealed that these samples crystallize in a perovskite-like LaNiO3 structure. HRSEM images revealed that the samples prepared with different deposition times (0.5, 1 and 2 h) promoted the formation of LaNiO3 nanotubes with different wall thicknesses.

Top quark mass measurement in the lepton plus jets channel using a modified matrix element method

We report a measurement of the top quark mass, m_t, obtained from ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb^-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, with effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of m_t and a parameter JES that determines /in situ/ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find m_t = 172.7 +/- 1.8 (stat. + JES) +/- 1.2 (syst.) GeV/c^2.

Quantitative genetic modeling of lateral ventricular shape and volume using multi-atlas fluid image alignment in twins

Despite substantial progress in measuring the 3D profile of anatomical variations in the human brain, their genetic and environmental causes remain enigmatic. We developed an automated system to identify and map genetic and environmental effects on brain structure in large brain MRI databases . We applied our multi-template segmentation approach ("Multi-Atlas Fluid Image Alignment") to fluidly propagate hand-labeled parameterized surface meshes into 116 scans of twins (60 identical, 56 fraternal), labeling the lateral ventricles. Mesh surfaces were averaged within subjects to minimize segmentation error. We fitted quantitative genetic models at each of 30,000 surface points to measure the proportion of shape variance attributable to (1) genetic differences among subjects, (2) environmental influences unique to each individual, and (3) shared environmental effects. Surface-based statistical maps revealed 3D heritability patterns, and their significance, with and without adjustments for global brain scale. These maps visualized detailed profiles of environmental versus genetic influences on the brain, extending genetic models to spatially detailed, automatically computed, 3D maps.

Template-free electrochemical nanofabrication of polyaniline nanobrush and hybrid polyaniline with carbon nanohorns for supercapacitors.

Polyaniline (PANI) nanobrushes were synthesized by template-free electrochemical galvanostatic methods. When the same method was applied to the carbon nanohorn (CNH) solution containing aniline monomers, a hybrid nanostructure containing PANI and CNHs was enabled after electropolymerization. This is the first report on the template-free method to make PANI nanobrushes and homogeneous hybrid soft matter (PANI) with carbon nanoparticles. Raman spectroscopy was used to analyze the interaction between CNH and PANI. Electrochemical nanofabrication offers simplicity and good control when used to make electronic devices. Both of these materials were applied in supercapacitors and an improvement capacitive current by using the hybrid material was observed.

One-step synthesis of 3D dendritic gold/polypyrrole nanocomposites via a self-assembly method

Novel spherical three-dimensional (3D) dendritic gold-polypyrrole nanocomposites were successfully prepared in the presence of an amphiphilic p-toluene sulfonic acid (TSA) as dopant and surfactant via a self-assembly process which is based on the oxidation of pyrrole (Py) and the reduction of the chloroaurate ions, yielding PPy and Au(0) simultaneously. It was found that the probability of obtaining dendritic Au@PPy/TSA nanostructures depended on the concentration of TSA and the rate of addition of the oxidant (HAuCl4), It was also proposed that the supramolecular micelles formed by Py and TSA play the role of a 'soft template' to produce the dendritic Au@PPy/TSA nanocomposites.

An Active Learning Module for an Introduction to Software Engineering Course

Many schools do not begin to introduce college students to software engineering until they have had at least one semester of programming. Since software engineering is a large, complex, and abstract subject it is difficult to construct active learning exercises that build on the students’ elementary knowledge of programming and still teach basic software engineering principles. It is also the case that beginning students typically know how to construct small programs, but they have little experience with the techniques necessary to produce reliable and long-term maintainable modules. I have addressed these two concerns by defining a local standard (Montana Tech Method (MTM) Software Development Standard for Small Modules Template) that step-by-step directs students toward the construction of highly reliable small modules using well known, best-practices software engineering techniques. “Small module” is here defined as a coherent development task that can be unit tested, and can be car ried out by a single (or a pair of) software engineer(s) in at most a few weeks. The standard describes the process to be used and also provides a template for the top-level documentation. The instructional module’s sequence of mini-lectures and exercises associated with the use of this (and other) local standards are used throughout the course, which perforce covers more abstract software engineering material using traditional reading and writing assignments. The sequence of mini-lectures and hands-on assignments (many of which are done in small groups) constitutes an instructional module that can be used in any similar software engineering course.

A competition-based deformable template for junction extraction

Comunicación presentada en el VIII Simposium Nacional de Reconocimiento de Formas y Análisis de Imágenes, Bilbao, mayo 1999.

Porous, catalytically active palladium nanostructures by tuning nanoparticle interactions in an organic medium

We present a simple template-free method for the synthesis of interconnected hierarchical porous palladium nanostructures by controlling the aggregation of nanoparticles in organic media. The interaction between the nanoparticles is tuned by varying the dielectric constant of the medium consistent with DLVO calculations. The reaction products range from discrete nanoparticles to compact porous clusters with large specific surface areas. The nanoclusters exhibit hierarchical porosity and are found to exhibit excellent activity towards the reduction of 4-nitrophenol into 4-aminophenol and hydrogen oxidation. The method opens up possibilities for synthesizing porous clusters of other functional inorganics in organic media.

Synthesis, structural characterization and ferroelectric properties of Pb(0.76)Ca(0.24)TiO(3) nanotubes

A capillary-enforced template-based method has been applied to fabricate Pb(0.76)Ca(0.24)TiO(3) (PCT24) nanotubes via filling PCT24 precursor solution, prepared by modified sol-gel method, into nanochannels of anodic aluminum oxide templates. The morphology and structure of as-prepared PCT24 were examined by scanning electron microscopy, transmission electron microscopy (TEM) and X-ray diffraction techniques. The obtained PCT24 nanotubes with diameter of similar to 200 nm and wall thickness of similar to 20 nm exhibited a tetragonal perovskite structure. High resolution TEM (HRTEM) analysis confirmed that as-obtained PCT24 nanotubes made up of nanoparticles (5-8 nm) which were randomly aligned in the nanotubes. Formation of some solid crystalline PCT24 nanorods, Y-junctions and multi-branches were observed. Interconnections in the pores of template are responsible for the growth of Y-junctions and multi-branches. The possible formation mechanism of PCT24 nanotubes/nanorods was discussed. Ferroelectric hysteresis loops of PCT24 nanotube arrays were measured, showing a room temperature ferroelectric characteristic of as-prepared PCT24 nanotubes. (C) 2011 Elsevier B.V. All rights reserved.

Stability of ZrTiCuNiBe Bulk Metallic Glass Upon Isothermal Annealing Near the Glass Transition Temperature

The stability of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) upon isothermal annealing near the glass transition temperature has been investigated by using x-ray diffraction, differential scanning calorimetry, and the pulse echo overlap method. The density, elastic constants, and thermodynamic parameters as well as their annealing time dependence have been determined. The microstructural and properties changes of the annealed BMG were checked by acoustic measurement. Obvious structural and property changes were observed with prolonged annealing of the BMG near the glass transition temperature.

Preparation and characterization of CdS nanotubes and nanowires by electrochemical synthesis in ion-track templates

CdS nanotubes and nanowires have been synthesized with controlled dimensions by means of template-electrodeposition method in etched ion-track membranes. The diameters of nanotubes and nanowires are between 20 and I 10 nm, and the lengths are up to tens of micrometers. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern investigations demonstrate that CdS nanotubes and nanowires are polycrystalline in nature. The UV-vis absorption spectra of CdS nanotubes and nanowires embedded in polycarbonate (PC) membranes show that the absorption edges of PC films shift towards the shorter wavelength, with decreasing diameters of the deposited nanostructures. The results indicate that nanowires are formed from nanotubes by nanotube-stuffing-growth mechanism.

Segmented All-Platinum Nanowires with Controlled Morphology through Manipulation of the Local Electrolyte Distribution in Fluidic Nanochannels during Electrodeposition

Synthesis of segmented all-Pt nanowires is achieved by a template-assisted method. The combination of a suitably chosen electrolyte/template system with pulse-reverse electrodeposition allows the formation of well-defined segments linked to nanowires. Manipulation of the morphology is obtained by controlling the electrokinetie effects on the local electrolyte distribution inside the nanochannels during the nanowire growth process, allowing a deviation from the continuously cylindrical geometry given by the nanoporous template. The length of the segments can be adjusted as a function of the cathodic pulse duration. Applying constant pulses leads to segments with homogeneous shape and dimensions along most of the total wire length. X-ray diffraction demonstrates that the preferred crystallite orientation of the polycrystalline wires varies with the average segment length. The results are explained considering transitions in texture formation with increasing thickness of the electrodeposit. A mechanism of segment formation is proposed based on structural characterizations. Nanowires with controlled segmented morphology are of great technological importance, because of the possibility to precisely control their substructure as a means of tuning their electrical, thermal, and optical properties. The concept we present in this work for electrodeposited platinum and track-etched polycarbonate membranes can be applied to other selected materials as well as templates and constitutes a general method to controlled nanostructuring and synthesis of shape controlled nanostructures.