Measurement of the charge asymmetry in top-quark pair production in proton-proton collisions at s=7\sqrt{s}=7 TeV

The difference in angular distributions between top quarks and antiquarks, commonly referred to as the charge asymmetry, is measured in pp collisions at the LHC with the CMS experiment. The data sample corresponds to an integrated luminosity of 1.09 inverse femtobarns at a centre-of-mass energy of 7 TeV. Top-quark pairs are selected in the final state with an electron or muon and four or more jets. At least one jet is identified as originating from b-quark hadronization. The charge asymmetry is measured in two variables, one based on the pseudorapidities (eta) of the top quarks and the other on their rapidities (y). The results A[C,eta] = -0.017 +/- 0.032 (stat.) + [+0.025/-0.036] (syst.) and A[C,y] = -0.013 +/- 0.028 (stat.) + [+0.029/-0.031] (syst.) are consistent within uncertainties with the standard-model predictions.Peer Reviewe

Study of high-pT charged particle suppression in PbPb compared to pppp collisions at sNN=2.76\sqrt{s_{NN}}=2.76 TeV

The transverse momentum spectra of charged particles have been measured in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV by the CMS experiment at the LHC. In the transverse momentum range pt = 5-10 GeV/c, the charged particle yield in the most central PbPb collisions is suppressed by up to a factor of 5 compared to the pp yield scaled by the number of incoherent nucleon-nucleon collisions. At higher pt, this suppression is significantly reduced, approaching roughly a factor of 2 for particles with pt in the range pt=40-100 GeV/c.Peer Reviewe

Measurement of the Production Cross Section for Pairs of Isolated Photons in pppp collisions at s=7\sqrt{s}=7 TeV

The integrated and differential cross sections for the production of pairs of isolated photons is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 36 inverse picobarns is analysed. A next-to-leading-order perturbative QCD calculation is compared to the measurements. A discrepancy is observed for regions of the phase space where the two photons have an azimuthal angle difference, $\Delta(\phi)$, less than approximately 2.8.Peer Reviewe

Search for signatures of extra dimensions in the diphoton mass spectrum at the Large Hadron Collider

A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at sqrt(s) = 7 TeV corresponding to an integrated luminosity of 2.2 inverse femtobarns. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.Peer Reviewe

Ratios of dijet production cross sections as a function of the absolute difference in rapidity between jets in proton-proton collisions at s=7\sqrt{s}=7 TeV

A study of dijet production in proton-proton collisions was performed at sqrt(s) = 7 TeV for jets with pt > 35 GeV and abs(y) < 4.7 using data collected with the CMS detector at the LHC in 2010. Events with at least one pair of jets are denoted as 'inclusive'. Events with exactly one pair of jets are called 'exclusive'. The ratio of the cross section of all pairwise combinations of jets to the exclusive dijet cross section as a function of the rapidity difference between jets abs(Delta(y)) is measured for the first time up to abs(Delta(y)) = 9.2. The ratio of the cross section for the pair consisting of the most forward and the most backward jet from the inclusive sample to the exclusive dijet cross section is also presented. The predictions of the Monte Carlo event generators PYTHIA6 and PYTHIA8 agree with the measurements. In both ratios the HERWIG++ generator exhibits a more pronounced rise versus abs(Delta(y)) than observed in the data. The BFKL-motivated generators CASCADE and HEJ+ARIADNE predict for these ratios a significantly stronger rise than observed.Peer Reviewe

A New Boson with a Mass of 125 GeV Observed with the CMS Experiment at the Large Hadron Collider

Peer Reviewe

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Studies of the discovery potential for Minimal Universal Extra Dimensions in the four lepton final state in proton-proton collisions at the Large Hadron Collider with the CMS detector

Minimal Universal Extra Dimensions (MUED) models predict the presence of massive Kaluza-Klein particles with final states containing Standard Model leptons and jets. The multi-lepton final states provide the cleanest signature. The ability of the Compact Muon Solenoid (CMS) detector of the Large Hadron Collider (LHC) to find MUED final state signatures with four electrons, four muons, or two electrons and two muons was studied for four values of the compactification radius scale 1/R. The study was based on detailed Monte Carlo simulation of the physics interactions and detector performance. A center-of-mass energy of 14 TeV for the LHC was assumed. A simple and robust event selection, developed to discriminate MUED signature from instrumental and Standard Model backgrounds, as well as methods to control backgrounds estimates from data are presented. Results show that the CMS experiment is sensitive to MUED signatures up to 1/R=475 GeV/c$^{2}$ for an integrated luminosity of 1 fb$^{-1}$ and up to 1/R=900 GeV/c$^{2}$ for less than 30 fb$^{-1}$ of data

Selection of Top-like events in pp collisions at sqrt(s) = 7 TeV in early CMS data

Studies are presented of the selection of events consistent with top quark pair production in data recorded by the CMS detector at the LHC, corresponding to an integrated luminosity of 0.84 pb$^{-1}$ and a center-of-mass energy $\sqrt{s}$ = 7 TeV. Results are presented for the lepton+jets and dilepton channels. Events yields in data are compared to those in simulation and several background processes are estimated using data-driven techniques. The observed yields of top-antitop candidate events are roughly consistent with the Standard Model