108 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
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
Metamorphosis of Subarachnoid Hemorrhage Research: from Delayed Vasospasm to Early Brain Injury
Delayed vasospasm that develops 3–7 days after aneurysmal subarachnoid hemorrhage (SAH) has traditionally been considered the most important determinant of delayed ischemic injury and poor outcome. Consequently, most therapies against delayed ischemic injury are directed towards reducing the incidence of vasospasm. The clinical trials based on this strategy, however, have so far claimed limited success; the incidence of vasospasm is reduced without reduction in delayed ischemic injury or improvement in the long-term outcome. This fact has shifted research interest to the early brain injury (first 72 h) evoked by SAH. In recent years, several pathological mechanisms that activate within minutes after the initial bleed and lead to early brain injury are identified. In addition, it is found that many of these mechanisms evolve with time and participate in the pathogenesis of delayed ischemic injury and poor outcome. Therefore, a therapy or therapies focused on these early mechanisms may not only prevent the early brain injury but may also help reduce the intensity of later developing neurological complications. This manuscript reviews the pathological mechanisms of early brain injury after SAH and summarizes the status of current therapies
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
The Effect of Phosphodiesterase Inhibitor Tadalafil on Vasospasm Following Subarachnoid Hemorrhage in an Experimental Rabbit Model
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