Search for Top Squarks in R-Parity-Violating Supersymmetry Using Three or More Leptons and b-Tagged Jets

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at=2.76 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Event activity dependence of (nS) production in=5.02 TeV pPb and=2.76 TeV pp collisions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for new physics in events with same-sign dileptons and jets in pp collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for W ' -> tb decays in the lepton plus jets final state in pp collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for exclusive or semi-exclusive gamma gamma production and observation of exclusive and semi-exclusive e(+)e(-) production in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for WW gamma and WZ gamma production and constraints on anomalous quartic gauge couplings in pp collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for supersymmetry with razor variables in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of vector boson scattering and search for new physics in events with two same-sign leptons and two jets

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of final-state radiation in decays of Z bosons produced in pp collisions at 7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at root s=7TeV

A measurement of differential cross sections for the production of a pair of isolated photons in proton-proton collisions at root s = 7 TeV is presented. The data sample corresponds to an integrated luminosity of 5.0 fb(-1) collected with the CMS detector. A data-driven isolation template method is used to extract the prompt diphoton yield. The measured cross section for two isolated photons, with transverse energy above 40 and 25 GeV respectively, in the pseudorapidity range vertical bar eta vertical bar < 2.5, vertical bar eta vertical bar (sic) [1.44, 1.57] and with an angular separation Delta R > 0.45, is 17.2 +/-0.2 (stat) +/-1.9 (syst) +/- 0.4 (lumi) pb. Differential cross sections are measured as a function of the diphoton invariant mass, the diphoton transverse momentum, the azimuthal angle difference between the two photons, and the cosine of the polar angle in the Collins-Soper reference frame of the diphoton system. The results are compared to theoretical predictions at leading, next-to-leading, and next-to-next-to-leading order in quantum chromodynamics.

Search for anomalous production of events with three or more leptons in pp collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of top quark pairs production cross-section in the semi-leptonic channel with the ATLAS experiment

This thesis is about three major aspects of the identification of top quarks. First comes the understanding of their production mechanism, their decay channels and how to translate theoretical formulae into programs that can simulate such physical processes using Monte Carlo techniques. In particular, the author has been involved in the introduction of the POWHEG generator in the framework of the ATLAS experiment. POWHEG is now fully used as the benchmark program for the simulation of ttbar pairs production and decay, along with MC@NLO and AcerMC: this will be shown in chapter one. The second chapter illustrates the ATLAS detectors and its sub-units, such as calorimeters and muon chambers. It is very important to evaluate their efficiency in order to fully understand what happens during the passage of radiation through the detector and to use this knowledge in the calculation of final quantities such as the ttbar production cross section. The last part of this thesis concerns the evaluation of this quantity deploying the so-called "golden channel" of ttbar decays, yielding one energetic charged lepton, four particle jets and a relevant quantity of missing transverse energy due to the neutrino. The most important systematic errors arising from the various part of the calculation are studied in detail. Jet energy scale, trigger efficiency, Monte Carlo models, reconstruction algorithms and luminosity measurement are examples of what can contribute to the uncertainty about the cross-section.

Supersymmetry searches in the single lepton final state with the ATLAS detector

This thesis presents an analysis for the search of Supersymmetry with the ATLAS detector at the LHC. The final state with one lepton, several coloured particles and large missing transverse energy was chosen. Particular emphasis was placed on the optimization of the requirements for lepton identification. This optimization showed to be particularly useful when combining with multi-lepton selections. The systematic error associated with the higher order QCD diagrams in Monte Carlo production is given particular focus. Methods to verify and correct the energy measurement of hadronic showers are developed. Methods for the identification and removal of mismeasurements caused by the detector are found in the single muon and four jet environment are applied. A new detector simulation system is shown to provide good prospects for future fast Monte Carlo production. The analysis was performed for $35pb^{-1}$ and no significant deviation from the Standard Model is seen. Exclusion limits subchannel for minimal Supergravity. Previous limits set by Tevatron and LEP are extended.