198 research outputs found
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.Comment: 20 pages, 4 figures, submitted to PR
Measurement of the B0 anti-B0 oscillation frequency using l- D*+ pairs and lepton flavor tags
The oscillation frequency Delta-md of B0 anti-B0 mixing is measured using the
partially reconstructed semileptonic decay anti-B0 -> l- nubar D*+ X. The data
sample was collected with the CDF detector at the Fermilab Tevatron collider
during 1992 - 1995 by triggering on the existence of two lepton candidates in
an event, and corresponds to about 110 pb-1 of pbar p collisions at sqrt(s) =
1.8 TeV. We estimate the proper decay time of the anti-B0 meson from the
measured decay length and reconstructed momentum of the l- D*+ system. The
charge of the lepton in the final state identifies the flavor of the anti-B0
meson at its decay. The second lepton in the event is used to infer the flavor
of the anti-B0 meson at production. We measure the oscillation frequency to be
Delta-md = 0.516 +/- 0.099 +0.029 -0.035 ps-1, where the first uncertainty is
statistical and the second is systematic.Comment: 30 pages, 7 figures. Submitted to Physical Review
Measurement of the Associated Production Cross Section in Collisions at TeV
We present the first measurement of associated direct photon + muon
production in hadronic collisions, from a sample of 1.8 TeV
collisions recorded with the Collider Detector at Fermilab. Quantum
chromodynamics (QCD) predicts that these events are primarily from the Compton
scattering process , with the final state charm quark producing
a muon. Hence this measurement is sensitive to the charm quark content of the
proton. The measured cross section of is compared to a
leading-order QCD parton shower model as well as a next-to-leading-order QCD
calculation.Comment: 12 pages, 4 figures Added more detailed description of muon
background estimat
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.Comment: 14 pages, 2 figures. Available from the CDF server (PS with figs):
http://www-cdf.fnal.gov/physics/pub98/cdf4674_omega_t_prl_4.ps
FERMILAB-PUB-98/321-
A Measurement of the Differential Dijet Mass Cross Section in p-pbar Collisions at sqrt{s}=1.8 TeV
We present a measurement of the cross section for production of two or more
jets as a function of dijet mass, based on an integrated luminosity of 86 pb^-1
collected with the Collider Detector at Fermilab. Our dijet mass spectrum is
described within errors by next-to-leading order QCD predictions using CTEQ4HJ
parton distributions, and is in good agreement with a similar measurement from
the D0 experiment.Comment: 18 pages including 2 figures and 3 tables. Submitted to Phys. Rev. D
Rapid Communication
Search for New Particles Decaying to top-antitop in proton-antiproton collisions at squareroot(s)=1.8 TeV
We use 106 \ipb of data collected with the Collider Detector at Fermilab to
search for narrow-width, vector particles decaying to a top and an anti-top
quark. Model independent upper limits on the cross section for narrow, vector
resonances decaying to \ttbar are presented. At the 95% confidence level, we
exclude the existence of a leptophobic \zpr boson in a model of
topcolor-assisted technicolor with mass M_{\zpr} 480 \gev for natural
width = 0.012 M_{\zpr}, and M_{\zpr} 780 \gev for =
0.04 M_{\zpr}.Comment: The CDF Collaboration, submitted to PRL 25-Feb-200
Observation of the B_c Meson in p-bar p Collisions at sqrt{s} = 1.8 TeV
We have observed bottom-charm mesons B_c via the decay mode Bc -> J/psi
lepton neutrino in 1.8 TeV p-bar p collisions using the CDF detector at the
Fermilab Tevatron. A fit of background and signal contributions to the J/psi +
lepton mass distribution yielded 20.4 +6.2 -5.5 events from B_c mesons. A fit
to the same distribution with background alone was rejected at the level of 4.8
standard deviations. We measured the B_c mass to be 6.40 +- 0.39 +- 0.13 GeVc^2
and the B_c lifetime to be tau(B_c) = 0.46 +0.18 -0.16 +- 0.03 ps. We measured
the production cross section times branching ratio for B_c -> J/psi lepton
neutrino relative to that for B+ -> J/psi K to be 0.132 +0.041 -0.037 (stat) +-
0.031 (syst) +0.032 -0.020 (lifetime).Comment: 13 pages, 3 figures. Submitted to Physical Review Letters. Available
at http://www-cdf.fnal.gov/physics/pub98/cdf4496_Bc_PRL.p
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 .Comment: 17 pages, Revtex, with one postscript figure. Submitted to Physical
Review Letter
Search for Neutral Supersymmetric Higgs Bosons in Collisions at TeV
We present the results of a search for neutral Higgs bosons produced in
association with quarks in
final states with pb of collisions at
TeV recorded by the Collider Detector at Fermilab. We find no
evidence of such a signal and the data is interpreted in the context of the
neutral Higgs sector of the Minimal Supersymmetric extension of the Standard
Model. With basic parameter choices for the supersymmetric scale and the stop
quark mixing, we derive 95% C.L. lower mass limits for neutral Higgs bosons for
\tb values in excess of 35.Comment: 2 tex files 3 figure
Measurement of the B0 B0-bar oscillation frequency using pi-B meson charge-flavor correlations in p p-bar collisions at sqrt{s} = 1.8 TeV
We present a measurement of the B0 B0-bar oscillation frequency using a
flavor tagging method based on correlations of B meson flavor with the charge
of other particles produced in p p-bar collisions at sqrt{s} = 1.8 TeV. Such
correlations are expected to arise from b quark hadronization and from B**
decays. We partially reconstruct B mesons using the semileptonic decays B0 ->
lepton D(*)- X. and B+ -> lepton D0-bar X$. From the oscillation frequency, we
obtain the mass difference between the two B0 mass eigenstates, Delta m_d =
0.471 {+0.078} {-0.068}(stat) +- 0.034 (syst) hbar ps-1, and measure the
efficiency and purity of this flavor tagging method for both charged and
neutral B mesons.Comment: 16 pages, 2 figures. Submitted to Physical Review Letters. Also
available at
http://www-cdf.fnal.gov/physics/pub97/cdf4244_lepd_mix_sst_prl.p
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