SEARCHING FOR PHYSICS BEYOND THE STANDARD MODEL IN ATLAS WITH THE THIRD GENERATION QUARKS

ATLAS (A Toroidal LHC Apparatus) is one of the general-purpose detectors at the CERN's Large Hadron Collider (LHC), designed to study proton- proton collisions at a center of mass energy of 14 TeV. This PhD thesis starts with a performance measurement of the Inner Detector, followed by the measurement of an interesting Standard Model process on early data in which tracking and b-tagging play a fundamental role. Finally a search for new physics on the high integrated luminosity sample is presented. It includes a detailed measurement of the tracks impact parameter resolution as a function on the pseudorapidity \u3b7, the pT and the number of hits and shared hits in the silicon detectors of the tracks. The transverse impact parameter is measured to be ~10 \u3bcm for high pT tracks (pT>20 GeV) in a central \u3b7 region with one hit in the innermost pixel layer (b-layer) and without shared hits with other tracks in the silicon detectors. Two measurements are then presented, that profit of this excellent resolution and the related b-tagging performance. The first measurement of the charge asymmetry in the production of top quark pairs in the semileptonic decay channel. A dataset corresponding to an integrated luminosity of 1.04 fb-1, obtained at a centre-of-mass energy of 1as=7 TeV is used. The charge asymmetry is determined using the differential distribution of the reconstructed observable|yt|-|yT|, where yt and yT denote the top and antitop quark rapidities, respectively. The total charge asymmetry after unfolding is measured to be -0.019 \ub1 0.028 (stat.) \ub1 0.024 (syst.) in agreement with the Standard Model prediction of (0.60\ub10.03)%. Finally, the results of a search for direct pair production of supersymmetric partners of the top quark in 4.7 fb-1 and 13.0 fb-1 of integrated luminosity from proton-proton collisions respectively collected at 7 TeV in 2011 and 8 TeV in 2012 are reported. Scalar top quarks decaying into a b-quark and a superymmetric chargino are searched for in events with two leptons in the final state. This events have a final state topology similar that of top-antitop events and this analysis builds up on the experience that I gained with the top-antitop charge asymmetry measurement. No excess above the Standard Model expectation is observed. A scalar top with mass between 150 and 450 GeV is excluded at 95% CL for a chargino approximately degenerate with the scalar top and a massless ligthest neutralino

Agronomic and chemical characterization of soybean genotypes for human consumption.

Soybean (Glycine max (L) Merrill) presents a high level of good quality protein and lipids that consist mainly of unsaturated fatty acids. It also has considerable amounts of B complex vitamins and minerals such as iron, potassium and magnesium (Carrão-Panizzi, 1987). In addition to these good nutritional characteristics, soybean for human consumption should have a sweet, nut-like flavor, pale colored seeds (tegument, hilum and cotyledon) and suitable seed size for use as food (Destro, 1991; Vello, 1992). This research was carried out to describe the agronomic and chemical characteristics of food-type soybean genotypes for later use as cultivars or in crosses. Seventy-two soybean genotypes were used in the study, and the agronomic quantitative, qualitative and chemical traits of the grains were assessed, including mineral composition, oil, protein, carbohydrates and ash contents. The results showed that there was great genetic diversity among the genotypes studied for all the agronomic characteristics assessed. The F 82-5782 genotype was outstanding, presenting yield compatible with commercial exploitation as well as large seeds. The Mikawashima genotype presented the highest carbohydrate contents, while the Toffumame II genotype showed the greatest P contents and was also among the six genotypes that presented the greatest K, Ca, Mg, S, Zn, Mn and protein values. These genotypes can be used as cultivars or in breeding programs to solve specific problems of nutrient shortage due to genetic traits

The ATLAS EventIndex: Full chain deployment and first operation

AbstractThe Event Index project consists in the development and deployment of a complete catalogue of events for experiments with large amounts of data, such as the ATLAS experiment at the LHC accelerator at CERN. Data to be stored in the EventIndex are produced by all production jobs that run at CERN or the GRID; for every permanent output file, a snippet of information, containing the file unique identifier and the relevant attributes for each event, is sent to the central catalogue. The estimated insertion rate during the LHC Run 2 is about 80 Hz of file records containing ∼15 kHz of event records. This contribution describes the system design, the initial performance tests of the full data collection and cataloguing chain, and the project evolution towards the full deployment and operation by the end of 2014

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30