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F. Abe

Publications and source records attributed to F. Abe.

At least 145 records · Page 8Linked to original sources
arXiv1998

Search for a Technicolor omega_T Particle in Events with a Photon and a b-quark Jet at CDF

If the Technicolor omega_T particle exists, a likely decay mode is omega_T -> gamma pi_T, followed by pi_T -> bb-bar, yielding the signature gamma bb-bar. We have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab Tevatron for events with a photon and two jets, where one of the jets must contain a secondary vertex implying the presence of a b quark. We find no excess of events above standard model expectations. We express the result of an exclusion region in the M_omega_T - M_pi_T mass plane.

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arXiv1998

Search for second generation leptoquarks in the dimuon plus dijet channel of p-pbar collisions at sqrt{s}=1.8 TeV

We report on a search for second generation leptoquarks (Phi_2) using a data sample corresponding to an integrated luminosity of 110 pb^{-1} collected at the Collider Detector at Fermilab. We present upper limits on the production cross section as a function of Phi_2 mass, assuming that the leptoquarks are produced in pairs and decay into a muon and a quark with branching ratio beta. Using a Next-to-Leading order QCD calculation, we extract a lower mass limit of M_{Φ_2} > 202 (160) GeV$/c^{2} at 95% confidence level for scalar leptoquarks with beta=1(0.5).

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arXiv1998

Measurement of the Top Quark Mass with the Collider Detector at Fermilab

We present a new measurement of the top quark mass in $t\bar t$ events in which both $W$ bosons from top quarks decay into lepton ($e ν,μν$). We use events collected by the CDF experiment from $p\bar p$ collisions at \sqrt s=1.8 TeV at the Tevatron collider. We measure a top quark mass of 167.4 \pm 10.3(stat) \pm 4.8(syst) GeV/c^2 from a sample of eight events. We combine this result with previous CDF measurements in other decay channels to obtain a mass value of 176.0 \pm 6.5 GeV/c^2.

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arXiv1998

Measurement of the $B^0_d - \bar{B}{^0_d}$ flavor oscillation frequency and study of same side flavor tagging of B mesons in $p\bar p$ collisions

$B^0_d$-$\bar{B}{}^0_d$ oscillations are observed in ``self-tagged'' samples of partially reconstructed $B$ mesons decaying into a lepton and a charmed meson collected in $p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV. A flavor tagging technique is employed which relies upon the correlation between the flavor of $B$ mesons and the charge of nearby particles. We measure the flavor oscillation frequency to be $Δm_d = 0.471 ^{+0.078}_{-0.068} \pm 0.034 ps^{-1}$. The tagging method is also demonstrated in exclusive samples of $B^+_u \to J/ψK^+$ and $B^0_d \to J/ψK^{*0}(892)$, where similar flavor-charge correlations are observed. The tagging characteristics of the various samples are compared with each other, and with Monte Carlo simulations.

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arXiv1998

Improved Measurement of the B- and B0-bar Meson Lifetimes Using Semileptonic Decays

The lifetimes of the B- and B0-bar mesons are measured using the partially reconstructed semileptonic decays B-bar -> D l- nu-bar X, where D is either a D0 or D*+ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992-95 and correspond to about 110 pb-1 of p-bar p collisions at sqrt(s)=1.8 TeV. We measure decay lengths and extract the lifetimes to be tau(B-) = 1.637 +/- 0.058 +0.045 -0.043 ps, tau(B0) = 1.474 +/- 0.039 +0.052 -0.051 ps, and the ratio of the lifetimes to be tau(B-)/tau(B0) = 1.110 +/- 0.056 +0.033 -0.030, where the first uncertainties are statistical and the second are systematic.

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arXiv1998

Search for Long-Lived Parents of Z Bosons in pbar-p Collisions at sqrt{s}=1.8 TeV

We search for new long-lived particles which decay to Z bosons by looking for Z->e+e- decays with displaced vertices. We find no evidence for parent particles of the Z with long lifetimes in 90 pb-1 of data from the CDF experiment at Fermilab. We set a cross section limit as a function of the lifetime of the parent particle for both a generic Z parent and a fourth-generation, charge -1/3 quark that decays into Z+b.

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arXiv1998

Measurement of the Top Quark Mass

We present a measurement of the top quark mass using a sample of t-tbar decays into an electron or a muon, a neutrino, and four jets. The data were collected in p-pbar collisions at sqrt(s)=1.8 TeV with the Collider Detector at Fermilab and correspond to an integrated luminosity of 109 pb^-1. We measure the top quark mass to be 175.9 +/- 4.8(stat.) +/- 4.9(syst.) GeV/c^2.

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arXiv1997

Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass distribution is obtained that is consistent with W decay and inconsistent with the background prediction by 3.3 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.

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arXiv1997

Measurement of the t-tbar Production Cross Section in p-pbar Collisions at sqrt(s)=1.8 TeV

We present a measurement of the t-tbar cross section in p-pbar collisions at sqrt(s)=1.8 TeV using an integrated luminosity of 109 pb-1 collected with the Collider Detector at Fermilab. The measurement uses t-tbar decays into final states which contain one or two high transverse momentum leptons and multiple jets, and final states which contain only jets. Using acceptances appropriate for a top quark mass of 175 GeV/c^2, we find sigma(t-tbar)=7.6 (+1.8 -1.5) pb .

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arXiv1997

The mu tau and e tau Decays of Top Quark Pairs Produced in p pbar Collisions at sqrt(s) = 1.8 TeV

We present evidence for dilepton events from t tbar production with one electron or muon and one hadronically decaying tau lepton from the decay t tbar -> (l nu_l) (tau nu_tau) b bbar, (l=e, mu), using the Collider Detector at Fermilab (CDF). In a 109 pb^-1 data sample of p pbar collisions at sqrt(s) = 1.8 TeV we expect ~1 signal event and a total background of ~2 events; we observe 4 candidate events (2 e tau and 2 mu tau). Three of these events have jets identified as b candidates, compared to an estimated background of 0.28+-0.02 events.

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arXiv1997

Search for New Particles Decaying to Dijets at CDF

We have used 106 pb^-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at the 95% confidence level models containing the following new particles: axigluons and flavor universal colorons with mass between 200 and 980 GeV/c, excited quarks with mass between 80 and 570 GeV/c^2 and between 580 and 760 GeV/c^2, color octet technirhos with mass between 260 and 480 GeV/c^2, W' bosons with mass between 300 and 420 GeV/c^2, and E_6 diquarks with mass between 290 and 420 GeV/c^2.

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arXiv1996

Measurement of Dijet Angular Distributions at CDF

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.

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arXiv1996

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

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.

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arXiv1996

Further Properties of High-Mass Multijet Events at the Fermilab Proton-Antiproton Collider

The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase-space. Multijet distributions corresponding to (4N-4) variables that span the N-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD Matrix Element calculations, and QCD parton shower Monte Carlo predictions suggests that 2 -> 2 scattering plus gluon radiation provides a good first approximation to the full LO QCD matrix element for events with three, four, or even five jets in the final state.

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arXiv1996

Properties of Jets in Z Boson Events from 1.8 TeV $\bar{p}p$ Collisions

We present a study of events with Z bosons and hadronic jets produced in $\bar{p}p$ collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 $Z \to e^+e^-$ decays from 106 pb$^{-1}$ of integrated luminosity collected using the CDF detector at the Tevatron Collider. The Z $+ \ge n$ jet cross sections and jet production properties have been measured for n = 1 to 4. The data compare well to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

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arXiv1996

Search for Chargino-Neutralino Production in \ppb\sp Collisions at $\sqrt{s} = 1.8$ TeV

We have searched for chargino-neutralino production (\chichi) in 1.8 TeV \ppb\sp collisions, followed by their leptonic decays \chione\dk\chizero\lnu\psp and \chitwo\dk\chizero\lplm. These trilepton events are expected within a framework of the Minimal Supersymmetric Standard Model (MSSM). In a 19.1 pb$^{-1}$ data sample collected with the Collider Detector at Fermilab, no trilepton events were observed. Upper limits on $σ(\ppb\dk\chichi)\cdot BR(\chichi\dk 3 \ell + X)$ were obtained for various MSSM parameter space regions, yielding new 95\% confidence level lower limits for the neutralino (\chitwo) mass which extended as high as 49 \mgev.

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arXiv1996

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

The inclusive jet differential cross section has been measured for jet transverse energies, $E_T$, from 15 to 440 GeV, in the pseudorapidity region 0.1$\leq | η| \leq $0.7. The results are based on 19.5 pb$^{-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 $E_T>200$ GeV is significantly higher than current predictions based on O($α_s^3$) perturbative QCD calculations. Various possible explanations for the high-$E_T$ excess are discussed.

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