143 research outputs found
Roles of AP-2 in clathrin-mediated endocytosis.
The notion that AP-2 clathrin adaptor is an essential component of an endocytic clathrin coat appears to conflict with recent observations that substantial AP-2 depletion, using RNA interference with synthesis of AP-2 subunits, fails to block uptake of certain ligands known to internalize through a clathrin-based pathway
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
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 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_{\Phi_2} > 202 (160) GeV$/c^{2} at 95% confidence level for scalar
leptoquarks with beta=1(0.5).Comment: 11 pages, 2 figure
Search for New Particles Decaying to b bbar in p pbar Collisions at sqrt{s}=1.8 TeV
We have used 87 pb^-1 of data collected with the Collider Detector at
Fermilab to search for new particles decaying to b bbar. We present
model-independent upper limits on the cross section for narrow resonances which
excludes the color-octet technirho in the mass interval 350 < M < 440 GeV/c^2.
In addition, we exclude topgluons, predicted in models of topcolor-assisted
technicolor, of width Gamma = 0.3 M in the mass range 280 < M < 670 GeV/c^2, of
width Gamma = 0.5 M in the mass range 340 < M < 640 GeV/c^2, and of width Gamma
= 0.7 M in the mass range 375 < M < 560 GeV/c^2.Comment: 17 pages in a LaTex generated postscript file, with one table and
four figures. Resubmitted to Physical Review Letters. Minor clarifications
were added to the text. The displayed normalization of the resonance models
in Figure 2 was modified to correspond to our 95% CL upper limit on the cross
section (instead of arbitrary normalization which was used previously). All
results are identical to those in the previous submissio
Search for a W' Boson via the Decay Mode W' -> mu nu in 1.8 TeV p-pbar Collisions
We report the results of a search for a W' boson produced in p-pbar
collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample
recorded by the Collider Detector at Fermilab. We consider the decay channel W'
-> mu nu and search for anomalous production of high transverse mass mu-nu
lepton pairs. We observe no excess of events above background and set limits on
the rate of W' boson production and decay relative to Standard Model W boson
production and decay using a fit of the transverse mass distribution observed.
If we assume Standard Model strength couplings of the W' boson to quark and
lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c**2
at 95% confidence level.Comment: 19 pages, 2 figure
Search for Scalar Top Quark Production in p-pbar Collisions at 1.8 TeV
We have searched for direct production of scalar top quarks at the Collider
Detector at Fermilab in 88 pb-1 of p anti-p collisions at s**(1/2) = 1.8 TeV.
We assume the scalar top quark decays into either a bottom quark and a chargino
or a bottom quark, a lepton, and a scalar neutrino. The event signature for
both decay scenarios is a lepton, missing transverse energy, and at least two
b-quark jets. For a chargino mass of 90 GeV/c2 and scalar neutrino masses of at
least 40 GeV/c2, we find no evidence for scalar top production and present
upper limits on the production cross section in both decay scenarios.Comment: 13 pages, 4 figure
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