Rio de Janeiro State University

About: Rio de Janeiro State University is a education organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 16631 authors who have published 30919 publications receiving 465753 citations. The organization is also known as: UERJ & Rio de Janeiro State University.

Measurement of differential top-quark-pair production cross sections in pp collisions at √s = 7TeV

Abstract: Normalised differential top-quark pair production cross sections are measured in pp collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector using data recorded in 2011 corresponding to an integrated luminosity of 5.0 inverse femtobarns. The measurements are performed in the lepton+jets decay channels (e+jets and mu+jets) and the dilepton decay channels (oppositely charged ee, mu mu, and e mu). The t t-bar differential cross section is measured as a function of kinematic properties of the final-state charged leptons and jets associated to b quarks, as well as those of the top quarks and the t t-bar system. The data are compared with several predictions from perturbative QCD calculations up to approximate next-to-next-to-leading-order precision. No significant deviations from the standard model are observed.

Measurement of the muon charge asymmetry in inclusive pp →w+X production at s =7TeV and an improved determination of light parton distribution functions

Abstract: Measurements of the muon charge asymmetry in inclusive pp to WX production at sqrt(s) = 7 TeV are presented. The data sample corresponds to an integrated luminosity of 4.7 inverse femtobarns recorded with the CMS detector at the LHC. With a sample of more than twenty million W to mu nu events, the statistical precision is greatly improved in comparison to previous measurements. These new results provide additional constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10E-3 to 10E-1. These measurements and the recent CMS measurement of associated W + charm production are used together with the cross sections for inclusive deep inelastic ep scattering at HERA in a next-to-leading-order QCD analysis. The determination of the valence quark distributions is improved, and the strange-quark distribution is probed directly through the leading-order process g + s to W + c in proton-proton collisions at the LHC.

Search for long-lived particles that decay into final states containing two electrons or two muons in proton-proton collisions at s =8TeV

Abstract: A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) inverse femtobarns in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at sqrt(s) = 8 TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle's mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV, each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV), the limits are in the range 2-50 fb. These limits are sensitive to Higgs boson branching fractions as low as 1E-4.