76 research outputs found

    Multiplicity and rapidity dependence of strange hadron production in pp, pPb, and PbPb collisions at the LHC

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    Combined search for anomalous pseudoscalar HW couplings in VH(H -> b(b)over-bar) production and H -> VV decay

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    Search for supersymmetry in electroweak production with photons and large missing transverse energy in pp collisions at √s=8TeV

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    Results are reported from a search for supersymmetry with gauge-mediated supersymmetry breaking in electroweak production. Final states with photons and large missing transverse energy ( ETmiss ) were examined. The data sample was collected in pp collisions at s=8TeV with the CMS detector at the LHC and corresponds to 7.4 fb−1 . The analysis focuses on scenarios in which the lightest neutralino has bino- or wino-like components, resulting in decays to photons and gravitinos, where the gravitinos escape undetected. The data were obtained using a specially designed trigger with dedicated low thresholds, providing good sensitivity to signatures with photons, ETmiss , and low hadronic energy. No excess of events over the standard model expectation is observed. The results are interpreted using the model of general gauge mediation. With the wino mass fixed at 10 GeV above that of the bino, wino masses below 710 GeV are excluded at 95% confidence level. Constraints are also set in the context of two simplified models, for which the analysis sets the lowest cross section limits on the electroweak production of supersymmetric particles

    Search for lepton flavour violating decays of the Higgs boson to eτ and eμ in proton–proton collisions at √s=8 TeV

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    A direct search for lepton flavour violating decays of the Higgs boson (H) in the H→eτH→eτ and H→eμH→eμ channels is described. The data sample used in the search was collected in proton–proton collisions at View the MathML sources=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 fb−1. No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H→eτ)<0.69%B(H→eτ)<0.69% and B(H→eμ)<0.035%B(H→eμ)<0.035%, are set at the 95% confidence level. The constraint set on B(H→eτ)B(H→eτ) is an order of magnitude more stringent than the existing indirect limits. The limits are used to constrain the corresponding flavour violating Yukawa couplings, absent in the standard model

    Observation of top quark pairs produced in association with a vector boson in pp collisions at s=8 √s=8TeV

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    Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb −1 , collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from t t ¯ W tt¯W or t t ¯ Z tt¯Z decays. The t t ¯ W tt¯W cross section is measured to be 382 − 102 + 117 fb with a significance of 4.8 standard deviations from the background-only hypothesis. The t t ¯ Z tt¯Z cross section is measured to be 242 − 55 + 65 fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the t t ¯ W tt¯W and t t ¯ Z tt¯Z cross sections

    Erratum: Measurement of the t(t)over-bar production cross section in the dilepton channel in pp collisions at root s = 8 TeV (vol 2, 024, 2014)

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    Search for a narrow, spin-2 resonance decaying to a pair of Z bosons in the qq+− final state

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    Evidence for the 125 GeV Higgs boson decaying to a pair of tau leptons

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    A search for a standard model Higgs boson decaying into a pair of &#964; leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of 4.9 fb &#8722;1 at a centre-of-mass energy of 7 TeV and 19.7 fb &#8722;1 at 8 TeV. Each &#964; lepton decays hadronically or leptonically to an electron or a muon, leading to six different final states for the &#964; -lepton pair, all considered in this analysis. An excess of events is observed over the expected background contributions, with a local significance larger than 3 standard deviations for m H values between 115 and 130 GeV. The best fit of the observed H &#8594; &#964; &#964; signal cross section times branching fraction for m H = 125 GeV is 0 . 78 ± 0 . 27 times the standard model expectation. These observations constitute evidence for the 125 GeV Higgs boson decaying to a pair of &#964; leptons

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

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    Search for charge-asymmetric production of W\u27 bosons in tt + jet events from pp collisions at √s = 7 TeV

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    A search is presented for charge-asymmetric production of a W boson that has been proposed to accommodate the forward–backward asymmetry observed in the production of top–antitop quark pairs at the Tevatron. The new heavy W‘ boson would be produced in association with a top quark and would decay into top and down quarks. The data correspond to an integrated luminosity of 5.0 fb−1 in pp collisions at a center-of-mass energy of 7 TeV, recorded by the CMS detector at the LHC. No significant excess above the standard model expectations is observed, and, from a combination of the electron-plusjets and muon-plus-jets channels, a 95% confidence level lower limit of 840 GeV/c2 is set on the W‘ boson mass for a W‘ boson model with values for coupling constants to top and down quarks gL = 0 and gR = 2. In addition, a kinematic reconstruction of the W‘ resonance mass using the inherent charge asymmetry of this model finds no indication of the presence of W‘ events in the data
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