277 research outputs found

    Direct search for heavy neutral gauge bosons in the dielectron channel at D0

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    Electroretinogram changes before and after silicone oil removal in eyes with macula-off rhegmatogenous retinal detachment

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    Background: Pars plana vitrectomy (PPV) with silicone oil (SO) injection for rhegmatogenous retinal detachment (RRD) repair may adversely affect electroretinographic responses. This study was aimed at assessing retinal function using electrodiagnostic testing after successful PPV with SO tamponade in the eyes with macula-off RRD. Methods: In this interventional comparative study, eligible participants were recruited prospectively over 1 year. We included the eyes that underwent a single successful three-port PPV with SO tamponade for the primary repair of macula-off RRD. Full-field electroretinogram (ffERG) and multifocal electroretinogram (mfERG) were recorded 1 day before and 3 days after SO removal. The amplitude and implicit time of the a- and b-waves for ffERG and P1 and N1 waves for mfERG were evaluated. The unaffected fellow eyes of the patients were selected as controls. Results: We included the ten eyes of ten patients (seven men and three women) with a mean (standard deviation) age of 58.8 (6.2) years. The mean (SD) interval between the diagnoses of macula-off RRD and PPV was 11.7 (3.6) days. The mean (SD) duration of SO tamponade was 147.8 (34.9) days. Using ffERG, significantly lower a- and b-wave amplitudes were found in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P < 0.05). Using the mfERG, treated eyes had significantly lower P1 amplitudes in the central R1+R2+R3 rings and in the R4 and-R5 peripheral rings of the macular area in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P < 0.05). The wave implicit time in ffERG and mfERG did not differ significantly in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P > 0.05). Conclusions: The electrical retinal response density in ERG waveforms increased following SO removal, indicating amelioration of the electrical activity of the retina and macula. These results indicate that the adverse effects of SO tamponade on electroretinography responses may be reversible with removal. In addition, ffERG and mfERG can be used to monitor retinal function in the eyes with macula-off RRD and SO tamponade. Further clinical trials are required to verify the preliminary findings of this study

    Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

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    We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

    Evidence for Simultaneous Production of J/ψ and ϒ Mesons

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    We report evidence for the simultaneous production of J/ψ and ϒ mesons in 8.1 fb−1 of data collected at √s = 1.96 TeV by the D0 experiment at the Fermilab p¯p Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, σeff = 2.2 ± 0.7(stat) ± 0.9(syst) mb

    Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

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    We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

    Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States

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    We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb-1 of pp̅ collisions at √s= 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L

    [?] lifetime measurement in the \u3ci\u3eCP\u3c/i\u3e-odd decay channel [?] → J/ψ f\u3ci\u3e0\u3c/i\u3e(980)

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    The lifetime of the [?] meson is measured in the decay channel [?] → J/ψπ+π− with 880 ≤ Mπ+π- - ≤ 1080 MeV / c2, which is mainly a CP-odd state and dominated by the f0 (980) resonance. In 10.4 fb-1 of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the [?] meson is measured to be [?] = 1.70 ± 0.14(stat) ± 0.05(syst) ps. Neglecting CP violation in [?]/[?] mixing, the measurement can be translated into the width of the heavy mass eigenstate of the [?], ΓH = 0.59 ± 0.05(stat) ± 0.02(syst) ps-1

    Measurement of the top quark mass using the matrix element technique in dilepton final states

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    We present a measurement of the top quark mass in pp collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb−1. The matrix element technique is applied to tt events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton + jets final state of tt decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt = 173.93 ± 1.84 GeV

    Search for a Fourth Generation tl Quark in pp̅ Collisions at √s= 1.96 TeV

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    We present a search for pair production of a fourth generation tl quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5.3 fb-1 of proton-antiproton collisions at √s= 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the tlt-l production cross section that exclude at the 95% C.L. a tl quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the µ + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal

    Direct measurement of the mass difference between top and antitop quarks

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    We present a direct measurement of the mass difference between top and antitop quarks (∆m) in lepton + jets tt final states using the ‘‘matrix element’’ method. The purity of the lepton + jets sample is enhanced for tt events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of pp collisions at √s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and µ + jets channels yields ∆m =0.8 ± 1,8 stat ± 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference
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