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  1. Forward-backward asymmetry in top quark-antiquark production

    Abazov, Victor Mukhamedovich - Physical Review. D, Particles, Fields, Gravitation and Cosmology
    We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%.more » The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.« less

  2. Top-quark mass measurement using events with missing transverse energy and jets at CDF

    Aaltonen, T. - Physical Review Letters
    We present a measurement of the top-quark mass with tt events using a data sample corresponding to an integrated luminosity of 5.7 fb -1 of pp collisions at the Fermilab Tevatron with √s = 1.96 TeV and collected by the CDF II Detector. We select events having no identified charged leptons, large missing transverse energy, and four, five, or six jets with at least one jet containing a secondary vertex consistent with the decay of a b quark. This analysis considers events from the semileptonic tt decay channel, including events that contain tau leptons, which are usually not included inmore » the top-quark mass measurements. The measurement uses as kinematic variables the invariant mass of two jets consistent with the mass of the W boson, and the invariant masses of two different three-jet combinations. We fit the data to signal templates of varying top-quark masses and background templates, and measure a top-quark mass of Mtop = 172.3 ± 2.4 (stat) ± 1.0 (syst) GeV/c2.« less

  3. Search for new physics in high pT like-sign dilepton events at CDF II

    Aaltonen, T. - Physical Review Letters
    We present a search for new physics in events with two high pT leptons of the same electric charge, using data with an integrated luminosity of 6.1 fb-1. The observed data are consistent with standard model predictions. We set 95% C.L. lower limits on the mass of doubly-charged scalars decaying to like-sign dileptons, mH±± > 190 - 245 GeV/c2, depending on the decay mode and coupling.

  4. Longitudinal bunch monitoring at the Fermilab Tevatron and Main Injector synchrotrons

    Thurman-Keup, R. ; Bhat, C. ; Blokland, W. ; ... - Journal of Instrumentation
    The measurement of the longitudinal behavior of the accelerated particle beams at Fermilab is crucial to the optimization and control of the beam and the maximizing of the integrated luminosity for the particle physics experiments. Longitudinal measurements in the Tevatron and Main Injector synchrotrons are based on the analysis of signals from resistive wall current monitors. This study describes the signal processing performed by a 2 GHz-bandwidth oscilloscope together with a computer running a LabVIEW program which calculates the longitudinal beam parameters.

  5. Measurement of branching ratio and B0s lifetime in the decay B0s → J/ψ f0(980) at CDF

    Aaltonen, T. - Physical Review. D, Particles, Fields, Gravitation and Cosmology
    We present a study of Bs0 decays to the CP-odd final state J/ψ f0(980) with J/ψ → µ+µ- and f0(980) → π+π-. Using pp̄ collision data with an integrated luminosity of 3.8 fb-1 collected by the CDF II detector at the Tevatron we measure a Bs0 lifetime of τ(B0s → J/ψ f0(980)) = 1.70-0.11+0.12(stat) ± 0.03(syst) ps. This is the first measurement of the Bs0} lifetime in a decay to a CP eigenstate and corresponds in the standard model to the lifetime of the heavy Bs0 eigenstate. We also measure the product of branching fractions of B0s → J/ψ f0(980)more » and f0(980) → π+π- relative to the product of branching fractions of B0s → J/ψφ and φ→K+K- to be Rf0/ψ = 0.257 ± 0.020(stat) ± 0.014(syst), which is the most precise determination of this quantity to date.« less

  6. Measurement of sin2 θℓeff and Z-light quark couplings using the forward-backward charge asymmetry in pp -> Z/gamma* -> e+e- events with L=5.0 fb-1 at √s=1.96 TeV

    Abazov, V. M. - Physical Review. D, Particles, Fields, Gravitation and Cosmology
    We measure the mass dependence of the forward-backward charge asymmetry in 157,553 pp = Z/γ* = e+e- interactions, corresponding to 5.0 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider at √s = 1.96 TeV. The effective weak mixing angle (θℓeff) from this process involving predominantly the first generation of quarks is extracted as sin2 θℓeff = 0.2309 ± 0.0008 (stat.) ± 0.0006 (syst.). We also present the most precise direct measurement of the vector and axial-vector couplings of u and d quarks to the Z boson.

  7. First Search for Multijet Resonances in $$\sqrt{s} = 1.96$$ TeV $$ p\bar{p}$$ Collisions

    Aaltonen, T. - Physical Review Letters
    We present the first model independent search for three-jet hadronic resonances within multijet events in $$\sqrt{s} = 1.96$$ TeV $$ p\bar{p}$$ collisions at the Fermilab Tevatron using the CDF II detector. Pair production of supersymmetric gluinos and squarks with hadronic R-parity violating decays is employed as an example of a new physics benchmark for this signature. Selection criteria based on the kinetmatic properties of an ensemble of jet combinations within each event help to extract signal from copious QCD background. Our background estimates include all-hadronic t{anti t} decays that have a signature similar to the signal. No significant excess outsidemore » the top quark mass window is observed in data with an integrated luminosity of 3.2 fb{sup -1}. We place 95% confidence level limits on the production cross section {sigma}(p{anti p} {yields} X X') x BR ((tilde gg) {yields} 3 jet + 3 jet) where X, X' = {tilde g}, {tilde q}, or {tilde {anti q}}, with {tilde q}, {tilde {anti q}} {yields} {tilde g} + jet, as a function of gluino mass, in the range of 77 GeV/c{sup 2} to 240 GeV/c{sup 2}.« less

  8. Top quark mass measurement using the template method at CDF

    Aaltonen, T - Physical Review. D, Particles, Fields, Gravitation and Cosmology
    We present a measurement of the top quark mass in the lepton+jets and dilepton channels of t$$\bar{t}$$ decays using the template method. The data sample corresponds to an integrated luminosity of 5.6 fb-1 of p$$\bar{p}$$ collisions at Tevatron with √s = 1.96 TeV, collected with the CDF II detector. The measurement is performed by constructing templates of three kinematic variables in the lepton+jets and two kinematic variables in the dilepton channel. The variables are two reconstructed top quark masses from different jets-to-quarks combinations and the invariant mass of two jets from the W decay in the lepton+jets channel, and amore » reconstructed top quark mass and mT2, a variable related to the transverse mass in events with two missing particles, in the dilepton channel. The simultaneous fit of the templates from signal and background events in the lepton+jets and dilepton channels to the data yields a measured top quark mass of Mtop = 172.1±1.1 (stat)±0.9 (syst) GeV/c2.« less

  9. Muon collider interaction region design

    Alexahin, Y. I. ; Gianfelice-Wendt, E. ; Kashikhin, V. V. ; ... - Physical Review Special Topics. Accelerators and Beams

  10. Measurement of the W charge asymmetry in the W → μ ν decay mode in pp collisions at s = 7   TeV with the ATLAS detector

    Aad, G. ; Abbott, B. ; Abdallah, J. ; ... - Physics Letters B
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