Preparação e Caracterização de Argilas Organofílicas e Sua Aplicação na Adsorção de Atrazina em Água

As argilas organofílicas preparadas a partir de sais quaternários de amônio destacam-se como adsorvente para separação de compostos orgânicos da água. Desta forma, o propósito deste trabalho foi preparar e caracterizar três diferentes tipos de argilas organofílicas e depois verificar a capacidade de uma dessas argilas em adsorver a atrazina em meio aquoso. A partir do processo de troca catiônica, promoveu-se a modificação da argila natural em argilas organofílicas, usando-se os surfactantes brometo de cetil trimetil amônio, cloreto de cetil trimetil amônio e cloreto de dodecil trimetil amônio. Para a argila in natura, os resultados da análise química por fluorescência de raio X apresentaram-se coerentes com os de um argilomineral esmectítico, assim como o resultado obtido pela capacidade de troca catiônica, que apresentou um valor de 80meq/100g de argila. Os dados de difração de raio X indicam diferentes expansões lamelares para as três argilas organofílicas obtidas quando comparadas à argila in natura, comprovando a presença dos sais quaternários de amônio no espaço interlamelar. Através da microscopia eletrônica de varredura foi possível verificar formação de aglomerações. Também foi verificada uma diminuição da área superficial específica demonstrando menor acessibilidade aos espaços lamelares devido à presença dos surfactantes. As análises termogravimétricas foram realizadas numa taxa constante de aquecimento até 1000ºC, obtendo-se perfil de variação negativa em todas as argilas, sendo possível constatar a perda de água e dos surfactantes gradativamente. O inchamento de Foster mostrou forte favorecimento de adsorção de solventes de características apolares, confirmando o caráter organofílico. Além disso, a adsorção da atrazina na argila organofílica escolhida foi bem maior se comparada com a argila in natura, evidenciando o potencial de uso desses materiais como alternativa aos tratamentos existentes para remoção de compostos orgânicos de água

Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at sqrt(s) = 13 TeV

The first measurements of production cross sections of polarized same-sign W±W± boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W± scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fbis set on the production cross section for longitudinally polarized same-sign W±W± boson pairs. The electroweak production of same-sign W±W± boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations

Azimuthal correlations within exclusive dijets with large momentum transfer in photon-lead collisions

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at √sNN=5.02 TeV, corresponding to an integrated luminosity of 0.38 nb−1, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects

Measurements of the associated production of a W boson and a charm quark in proton-proton collisions at sqrt(s) = 8 TeV

Measurements of the associated production of a W boson and a charm (c) quark in proton–proton collisions at a centre-of-mass energy of 8TeV are reported. The analysis uses a data sample corresponding to a total integrated luminosity of 19.7fb−1 collected by the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm quark jets are selected using distinctive signatures of charm hadron decays. The product of the cross section and branching fraction σ(pp→W+c+X)B(W→ℓν), where ℓ=e or μ, and the cross section ratio σ(pp→W++c¯+X)/σ(pp→W−+c+X) are measured in a fiducial volume and differentially as functions of the pseudorapidity and of the transverse momentum of the lepton from the W boson decay. The results are compared with theoretical predictions. The impact of these measurements on the determination of the strange quark distribution is assessed

Measurement of differential cross sections for the production of a Z boson in association with jets in proton-proton collisions at sqrt(s) = 13 TeV

measurement is presented of the production of Z bosons that decay into two electrons or muons in association with jets, in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS Collaboration at the LHC with an integrated luminosity of 35.9 fb −1 . The differential cross sections are measured as a function of the transverse momentum (p T ) of the Z boson and the transverse momentum and rapidities of the five jets with largest pT . The jet multiplicity distribution is measured for up to eight jets. The hadronic activity in the events is estimated using the scalar sum of the p T of all the jets. All measurements are unfolded to the stable-particle level and compared with predictions from various Monte Carlo event generators, as well as with expectations at leading and next-to-leading orders in perturbative quantum chromodynamics

Identification of hadronic tau lepton decays using a deep neural network

A new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons (τh) that originate from genuine tau leptons in the CMS detector against τh candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τh candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine τh to pass the discriminator against jets increases by 10–30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τh reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τh reconstruction method are validated with LHC proton-proton collision data at √s = 13 TeV

Search for new physics in the lepton plus missing transverse momentum final state in proton-proton collisions at sqrt(s) = 13 TeV

A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016-2018 and corresponding to an integrated luminosity of 138 fb(-1). No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W' bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W' boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak W parameter, are presented using LHC data for the first time. These results together with those from the direct W' resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements

Search for flavor-changing neutral current interactions of the top quark and Higgs boson in final states with two photons in proton-proton collisions at sqrt(s) = 13 TeV

Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1.) No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t -> Hu) and 0.073% (0.051%) for B(t -> Hc). These are the strictest upper limits yet determined