358 research outputs found
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-
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 Top-Quark Mass in All-Hadronic Decays in p pbar Collisions at CDF II
We present a measurement of the top-quark mass, , in the
all-hadronic decay channel . The analysis is performed using 310 pb of
=1.96 TeV collisions collected with the CDF II detector
using a multi-jet trigger. The mass measurement is based on an event-by-event
likelihood which depends on both the sample purity and the value of the
top-quark mass, using 90 possible jet-to-parton assignments in the six-jet
final state. The joint likelihood of 290 selected events yields a value of
=177.1 4.9 (stat.) 4.7 (syst.) GeV/.Comment: 7 pages, 2 figures and 1 table, Submitted to Phys. Rev. Let
Measurement of Lifetime and Decay-Width Difference in B0s -> J/psi phi Decays
We measure the mean lifetime, tau=2/(Gamma_L+Gamma_H), and the width
difference, DeltaGamma=Gamma_L-Gamma_H, of the light and heavy mass eigenstates
of the B0s meson, B0sL and B0sH, in B0s -> J/psi phi decays using 1.7 fb^-1 of
data collected with the CDF II detector at the Fermilab Tevatron ppbar
collider. Assuming CP conservation, a good approximation for the B0s system in
the Standard Model, we obtain DeltaGamma = 0.076^+0.059_-0.063 (stat.) +- 0.006
(syst.) ps^-1 and tau = 1.52 +- 0.04 (stat.) +- 0.02 (syst.) ps, the most
precise measurements to date. Our constraints on the weak phase and DeltaGamma
are consistent with CP conservation.
Dedicated to the memory of our dear friend and colleague, Michael P. Schmid
Forward-Backward Asymmetry in Top Quark Production in ppbar Collisions at sqrt{s}=1.96 TeV
Reconstructable final state kinematics and charge assignment in the reaction
ppbar->ttbar allows tests of discrete strong interaction symmetries at high
energy. We define frame dependent forward-backward asymmetries for the outgoing
top quark in both the ppbar and ttbar rest frames, correct for experimental
distortions, and derive values at the parton-level. Using 1.9/fb of ppbar
collisions at sqrt{s}=1.96 TeV recorded with the CDF II detector at the
Fermilab Tevatron, we measure forward-backward top quark production asymmetries
in the ppbar and ttbar rest frames of A_{FB,pp} = 0.17 +- 0.08 and A_{FB,tt} =
0.24 +- 0.14.Comment: 7 pages, 2 figures, submitted to Phys.Rev.Lett, corrected references
and change of tex
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
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 Pair Production of Scalar Top Quarks Decaying to a tau Lepton and a b Quark in ppbar Collisions at sqrt{s}=1.96 TeV
We search for pair production of supersymmetric top quarks (~t_1), followed
by R-parity violating decay ~t_1 -> tau b with a branching ratio beta, using
322 pb^-1 of ppbar collisions at sqrt{s}=1.96 TeV collected by the CDF II
detector at Fermilab. Two candidate events pass our final selection criteria,
consistent with the standard model expectation. We set upper limits on the
cross section sigma(~t_1 ~tbar_1)*beta^2 as a function of the stop mass
m(~t_1). Assuming beta=1, we set a 95% confidence level limit m(~t_1)>153
GeV/c^2. The limits are also applicable to the case of a third generation
scalar leptoquark (LQ_3) decaying LQ_3 -> tau b.Comment: 7 pages, 2 eps figure
Measurement of the Cross Section for Prompt Diphoton Production in p-pbar Collisions at sqrt(s) = 1.96 TeV
We report a measurement of the rate of prompt diphoton production in
collisions at using a data sample of 207
pb collected with the upgraded Collider Detector at Fermilab (CDF II).
The background from non-prompt sources is determined using a statistical method
based on differences in the electromagnetic showers. The cross section is
measured as a function of the diphoton mass, the transverse momentum of the
diphoton system, and the azimuthal angle between the two photons and is found
to be consistent with perturbative QCD predictions.Comment: 7 pages, 3 figures,revtex4. Version accepted by PRL, but with cross
section tables i
Observation of Bs-Bsbar Oscillations
We report the observation of Bs-Bsbar oscillations from a time-dependent
measurement of the Bs-Bsbar oscillation frequency Delta ms. Using a data sample
of 1 fb^-1 of p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II
detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed
hadronic Bs decays, 3100 partially reconstructed hadronic Bs decays, and 61500
partially reconstructed semileptonic Bs decays. We measure the probability as a
function of proper decay time that the Bs decays with the same, or opposite,
flavor as the flavor at production, and we find a signal for Bs-Bsbar
oscillations. The probability that random fluctuations could produce a
comparable signal is 8 X 10^-8, which exceeds 5 sigma significance. We measure
Delta ms = 17.77 +- 0.10 (stat) +- 0.07 (syst) ps^-1
and extract
|Vtd/Vts| = 0.2060 +- 0.0007 (exp) + 0.0081 - 0.0060 (theor).Comment: 9 pages, 5 figures, submitted to Physical Review Letter
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