216 research outputs found

    PROJETO PENSAR PARA PROGRAMAR: DESIGN PARTICIPATIVO NO ENSINO MÉDIO

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    O uso de abordagens envolvendo Gamificac¸ao no contexto educaci- ˜ onal tem se destacado por facilitar a aplicac¸ ˆ ao de atividades relacionadas ˜ a` Avaliac¸ao Formativa, que fornecem monitoramento cont ˜ ´ınuo e detalhado do progresso estudantil. No entanto, unificar essas metodologias nao˜ e uma tarefa ´ trivial. Nesse sentido, abordagens colaborativas como o Projeto Participativo emergem por fornecer maneiras de facilitar o desenvolvimento de ferramentas tecnologicas que atendem ´ as necessidades dos alunos. Assim, este artigo re- ` lata as experiencias obtidas durante um projeto de ensino com foco em unificar ˆ Gamificac¸ao e Avaliac¸ ˜ ao Formativa atrav ˜ es do Design Participativo, onde um ´ jogo 3D foi desenvolvido para facilitar a explicac¸ao de conceitos te ˜ oricos para ´ estudantes do ensino medio

    Search for long-lived particles decaying in the CMS muon detectors in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceA search for long-lived particles (LLPs) decaying in the CMS muon detectors is presented. A data sample of proton-proton collisions at s\sqrt{s} = 13 TeV corresponding to an integrated luminosity of 138 fb1^{-1} recorded at the LHC in 2016-2018, is used. The decays of LLPs are reconstructed as high multiplicity clusters of hits in the muon detectors. In the context of twin Higgs models, the search is sensitive to LLP masses from 0.4 to 55 GeV and a broad range of LLP decay modes, including decays to hadrons, τ\tau leptons, electrons, or photons. No excess of events above the standard model background is observed. The most stringent limits to date from LHC data are set on the branching fraction of the Higgs boson decay to a pair of LLPs with masses below 10 GeV. This search also provides the best limits for various intervals of LLP proper decay length and mass. Finally, this search sets the first limits at the LHC on a dark quantum chromodynamic sector whose particles couple to the Higgs boson through gluon, Higgs boson, photon, vector, and dark-photon portals, and is sensitive to branching fractions of the Higgs boson to dark quarks as low as 2×\times103^{-3}

    Search for the lepton flavor violating τ\tau \to 3μ\mu decay in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceA search for the lepton flavor violating τ\tau \to 3μ\mu decay is performed using proton-proton collision events at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2017-2018, corresponding to an integrated luminosity of 97.7 fb1^{-1}. Tau leptons produced in both heavy-flavor hadron and W boson decays are exploited in the analysis. No evidence for the decay is observed. The results of this search are combined with an earlier null result based on data collected in 2016 to obtain a total integrated luminosity of 131 fb1^{-1}. The observed (expected) upper limits on the branching fraction B\mathcal{B}(τ\tau \to 3μ\mu) at confidence levels of 90 and 95% are 2.9×\times108^{-8} (2.4×\times108^{-8}) and 3.6×\times108^{-8} (3.0×\times108^{-8}), respectively

    Search for production of a single vector-like quark decaying to tH or tZ in the all-hadronic final state in pp collisions at s\sqrt{s} = 13 TeV

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    International audienceA search for electroweak production of a single vector-like T quark in association with a bottom (b) quark in the all-hadronic decay channel is presented. This search uses proton-proton collision data at s\sqrt{s} = 13 TeV collected by the CMS experiment at the CERN LHC during 2016-2018, corresponding to an integrated luminosity of 138 fb1^{-1} The T quark is assumed to have charge 2/3 and decay to a top (t) quark and a Higgs (H) or Z boson. Event kinematics and the presence of jets containing b hadrons are used to reconstruct the hadronic decays of the t quark and H or Z boson. No significant deviation from the standard model prediction is observed in the data. The 95% confidence level upper limits on the product of the production cross section and branching fraction of a T quark produced in association with a b quark and decaying via tH or tZ range from 1260 to 68 fb for T quark masses of 600-1200 GeV

    Searches for violation of Lorentz invariance in tt \mathrm{t} \overline{\mathrm{t}} production using dilepton events in proton-proton collisions at s= \sqrt{s}= 13 TeV

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    A search for violation of Lorentz invariance in the production of top quark pairs (tt \mathrm{t} \overline{\mathrm{t}} ) is presented. The measured normalized differential tt \mathrm{t} \overline{\mathrm{t}} production cross section, as function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb1 ^{-1} , and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to bound the Lorentz-violating couplings to be in ranges of 1-8 × \times 103^{-3} at 68% confidence level. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up two orders of magnitude with respect to previous searches conducted at the Tevatron.A search for violation of Lorentz invariance in the production of top quark pairs (ttˉ\mathrm{t\bar{t}}) is presented. The measured normalized differential ttˉ\mathrm{t\bar{t}} production cross section, as function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb1^{-1}, and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to bound the Lorentz-violating couplings to be in ranges of 1 - 8 ×\times 103^{-3} at 68% confidence level. This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up two orders of magnitude with respect to previous searches conducted at the Tevatron

    Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton

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    International audienceA search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2-20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb1^{-1}. A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths VNV_{\ell\mathrm{N}} to each lepton generation \ell and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of VμN2>\lvert V_{\mu\mathrm{N}}\rvert^{2}\gt 5 (4)×\times107^{-7} are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm

    Combination of measurements of the top quark mass from data collected by the ATLAS and CMS experiments at s=7\sqrt{s}=7 and 8 TeV

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    International audienceA combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The data sets used correspond to an integrated luminosity of up to 5 and 201^{-1} of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak tt-channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is mtm_\mathrm{t} = 172.52 ±\pm 0.14 (stat) ±\pm 0.30 (syst) GeV, with a total uncertainty of 0.33 GeV

    Measurement of the production cross section of a Higgs boson with large transverse momentum in its decays to a pair of τ\tau leptons in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceA measurement of the production cross section of a Higgs boson with transverse momentum greater than 250 GeV is presented where the Higgs boson decays to a pair of τ\tau leptons. It is based on proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb1^{-1}. Because of the large transverse momentum of the Higgs boson the τ\tau leptons from its decays are boosted and produced spatially close, with their decay products overlapping. Therefore, a dedicated algorithm was developed to reconstruct and identify them. The observed (expected) significance of the measured signal with respect to the standard model background-only hypothesis is 3.5 (2.2) standard deviations. The product of the production cross section and branching fraction is measured to be 1.640.54+0.68^{+0.68}_{-0.54} times the standard model expectation. The fiducial differential production cross section is also measured as functions of the Higgs boson and leading jet transverse momenta. This measurement extends the probed large-transverse-momentum region beyond 600 GeV

    Combination of measurements of the top quark mass from data collected by the ATLAS and CMS experiments at s=7\sqrt{s}=7 and 8 TeV

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    International audienceA combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The data sets used correspond to an integrated luminosity of up to 5 and 201^{-1} of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak tt-channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is mtm_\mathrm{t} = 172.52 ±\pm 0.14 (stat) ±\pm 0.30 (syst) GeV, with a total uncertainty of 0.33 GeV

    Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThe central exclusive production of charged-hadron pairs in pp collisions at a centre-of-mass energy of 13\TeV is examined, based on data collected in a special high-β\beta^* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, mπ+πm_{\pi^+\pi^-}<\lt 0.7 GeV or mπ+πm_{\pi^+\pi^-}>\gt 1.8 GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and mπ+πm_{\pi^+\pi^-} are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities y\lvert y\rvert<\lt 2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton
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