208 research outputs found

    Search for charged Higgs decays of the top quark using hadronic tau decays

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    We present the result of a search for charged Higgs decays of the top quark, produced in ppˉp\bar{p} collisions at √s=\surd s = 1.8 TeV. When the charged Higgs is heavy and decays to a tau lepton, which subsequently decays hadronically, the resulting events have a unique signature: large missing transverse energy and the low-charged-multiplicity tau. Data collected in the period 1992-1993 at the Collider Detector at Fermilab, corresponding to 18.7±\pm0.7~pb−1^{-1}, exclude new regions of combined top quark and charged Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp; submitted to Phys. Rev.

    Inclusive jet cross section in pˉp{\bar p p} collisions at s=1.8\sqrt{s}=1.8 TeV

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    The inclusive jet differential cross section has been measured for jet transverse energies, ETE_T, from 15 to 440 GeV, in the pseudorapidity region 0.1â‰€âˆŁÎ·âˆŁâ‰€\leq | \eta| \leq 0.7. The results are based on 19.5 pb−1^{-1} of data collected by the CDF collaboration at the Fermilab Tevatron collider. The data are compared with QCD predictions for various sets of parton distribution functions. The cross section for jets with ET>200E_T>200 GeV is significantly higher than current predictions based on O(αs3\alpha_s^3) perturbative QCD calculations. Various possible explanations for the high-ETE_T excess are discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review Letter

    Measurement of Dijet Angular Distributions at CDF

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    We have used 106 pb^-1 of data collected in proton-antiproton collisions at sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular distributions in events with two jets in the final state. The angular distributions agree with next to leading order (NLO) predictions of Quantum Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at 95% confidence level (CL) a model of quark substructure in which only up and down quarks are composite and the contact interaction scale is Lambda_ud(+) < 1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6 TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to Physical Review Letters on September 17, 1996. Postscript file of full paper available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p

    Measurement of σ⋅B(W→eÎœ)\sigma \cdot B (W \to e \nu) and σ⋅B(Z0→e+e−)\sigma \cdot B(Z^0 \to e^+e^-) in ppˉp {\bar p} collisions at s=1.8\sqrt{s}=1.8 TeV

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    We present a measurement of σ⋅B(W→eÎœ)\sigma \cdot B(W \to e \nu) and σ⋅B(Z0→e+e−)\sigma \cdot B(Z^0 \to e^+e^-) in proton - antiproton collisions at s=1.8\sqrt{s} =1.8 TeV using a significantly improved understanding of the integrated luminosity. The data represent an integrated luminosity of 19.7 pb−1^{-1} from the 1992-1993 run with the Collider Detector at Fermilab (CDF). We find σ⋅B(W→eÎœ)=2.49±0.12\sigma \cdot B(W \to e \nu) = 2.49 \pm 0.12~nb and σ⋅B(Z0→e+e−)=0.231±0.012\sigma \cdot B(Z^0 \to e^+e^-) = 0.231 \pm 0.012~nb.Comment: Uses Latex, Article 12 point, figure appended as uuencoded file The full PostScript available via WWW at http://www-cdf.fnal.gov/physics/pub95/cdf3312_sigma_1a_prl_v3.p

    Ratios of bottom meson branching fractions involving J/psi mesons and determination of b quark fragmentation fractions

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    We report a measurement of the ratios of the decay rates of the B^+, B^0 and B^0_s mesons into exclusive final states containing a J/psi meson. The final states were selected from 19.6 pb^{-1} of p-pbar collisions recorded by the Collider Detector at Fermilab. These data are interpreted to determine the bquark fragmentation fractions f_u, f_d and f_s. We also determine the branching fractions for the decay modes B^+ --> J/psi K^+, B^+ --> J/psi K^*(892)^+, B^0 --> J/psi K^0, B^0 --> J/psi K^*(892)^0 and B_s^0 --> J/psi phi(1020). We discuss the implications of these measurements to B meson decay models.Comment: 40 pages with 5 figures. Submitted to Phys. Rev. D. PostScript also available at http://www-cdf.fnal.gov/physics/pub96/cdf3609_bfrag_br_prd.p

    Search for New Particles Decaying to Dijets in p-pbar Collisions at sqrt(s)=1.8 TeV

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    We have used 19 pb**-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at 95% confidence level models containing the following new particles: axigluons with mass between 200 and 870 GeV, excited quarks with mass between 80 and 570 GeV, and color octet technirhos with mass between 320 and 480 GeV.Comment: Submitted to Physical Review Letters in December 199

    DIRECT PHOTON PRODUCTION AT THE CERN ISR

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    A measurement of direct photon production in pp collisions at a center of mass energy ∝s=63 GeV is reported. Arrays of lead-glass calorimeters and multiwire proportional chambers were used as photon detectors. Data are presented in the transverse momentum range from 4.5 to 10 GeV/c and compared with QCD predictions. The event structure of this sample is compared with that of a set dominated by high transverse momentum π O ́'s. © 1989

    HIGH TRANSVERSE ENERGY AND HIGH TRANSVERSE-MOMENTUM EVENTS IN PPBAR AND PP INTERACTIONS AT THE CERN INTERSECTING STORAGE-RINGS

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    A comparison between pp and pp interactions at √s = 52.7 GeV is presented for a total neutral transverse energy (ETo) trigger and for a high transverse momentum (pT) neutral cluster trigger. The rate of production of events in the range

    DIRECT PHOTON PRODUCTION AT THE CERN ISR

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    A measurement of direct photon production in pp collisions at a center of mass energy ∝s=63 GeV is reported. Arrays of lead-glass calorimeters and multiwire proportional chambers were used as photon detectors. Data are presented in the transverse momentum range from 4.5 to 10 GeV/c and compared with QCD predictions. The event structure of this sample is compared with that of a set dominated by high transverse momentum π O ́'s. © 1989

    A STUDY OF ASSOCIATED PARTICLES AND 2ND-ORDER PROCESSES IN ELECTRON-PAIR PRODUCTION AT THE CERN INTERSECTING STORAGE-RINGS

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    The multiplicity of particles associated with electron pairs with mass greater than 11 GeV/c2 is found to increase with the transverse momentum pT of the electron pair. The associated particles are observed to recoil against the electron pair and compensate locally its transverse momentum. The data are compared with lower √s dimuon data using the scaling form: s2pT2(d3 σ/dy dpT2 dm2) = H (xT, y, τ). © 1984
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