Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the ...three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fbsuper-1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.
We present a search for associated production of Higgs and W bosons in inline image collisions at a center of mass energy of inline image in 5.3 fbsuper-1 of integrated luminosity recorded by the D0 ...experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for m sub(H=115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of inline image to its Standard Model prediction, which is consistent with an expected limit of 4.8.)
We present a search for electroweak production of single top quarks in the s-channel and t-channel using neural networks for signal-background separation. We have analyzed 230 pb(-1) of data ...collected with the DO detector at the Fermilab Tevatron Collider at a center-of-mass energy of 1.96 TeV and find no evidence for a single top quark signal. The resulting 95% confidence level upper limits on the single top quark production cross sections are 6.4 pb in the s-channel and 5.0 ph in the t-channel.
We present a measurement of the top quark pair (t (t) over bar) production cross section (sigma(t (t) over bar)) in pp collisions at root s = 1.96 TeV using 230 pb(-1) of data collected by the DO ...experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the t F purity of the selected sample. For a top quark mass of 175 GeV, we measure sigma(t (t) over bar) 8.6(-1.5)(+1.6) (stat. + syst.) +/- 0.6(lumi.) pb, in agreement with the standard model expectation.
We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fbsuper-1 of integrated luminosity collected with ...the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma sub(tgu0.20 pb and sigma) sub(t)gc0.27 pb. These correspond to limits on the top quark decay branching fractions of inline imageinline image and inline imageinline image.
We present a measurement of the top quark pair (t (t) over bar) production cross section (sigma(t (t) over bar)) in pp collisions at a center-of-mass energy of 1.96 TeV using 230 pb(-1) of data ...collected by the DO detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the t (t) over bar content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure sigma(t (t) over bar) 6.7(-1.3)(+1.4)(stat)(-1.1)(+1.6)(syst) +/- 0.4(lumi) pb, in good agreement with the standard model prediction.
The vegetation of twelve french rivers was studied to test the standardized protocol "Milieu Et Végétaux aquatiques fixés". Data processing for each river and then for all studied stretches gave ...floristic typologies and an assessment of the pattern of vegetation distribution. A wide diversity appeared upstream, due to geology and mineralization, flow and shade. Vegetation was more homogeneous downstream, following eutrophication and river with increase. The ecoregional features are mainly due to geology, then to distance from the sea and to opposition between foothill and lowland rivers. Results are discussed to improve the methodology, paying attention to reference phytocenosis concept.
La végétation de douze cours d'eau répartis sur le territoire français a été étudiée selon le protocole standardisé d'échantillonnage "Milieu Et Végétaux aquatiques fixés" (MEV) pour tester ce protocole. Le traitement des données par rivière puis pour l'ensemble des séquences étudiées permet d'établir des typologies floristiques. De façon préliminaire, le déterminisme de distribution des phytocénoses est envisagé. Les différences majeures s'expriment à l'amont en fonction de la géologie et de la minéralisation, des conditions d'écoulement et d'ombrage. Une homogénéisation s'effectue vers l'aval, à la faveur de l'eutrophisation et de l'accroissement des dimensions du cours d'eau. La dimension éco-régionale s'exprime d'abord au niveau de la géologie, et secondairement en fonction du climat (atlanticité) et des différences entre rivière de plaine et de piémont. Les résultats sont discutés en vue d'une amélioration du protocole et de la possibilité d'application de la notion de phytocénoses de référence.
The first observation of open
b production in
ep collisions is reported. An event sample containing muons and jets has been selected which is enriched in semileptonic
b quark decays. The visible ...cross section
σ(ep
→
b
b
̄
X
→
μ
X′)
for
Q
2<1
GeV
2
, 0.1<
y<0.8 is measured to be
0.176
±
0.016
(stat.)
+0.026
−0.017
(syst.)
nb
for the muons to be detected in the range 35°<
θ
μ
<130° and
p
⊥
μ>2.0
GeV
in the laboratory frame. The expected visible cross section based on a NLO QCD calculation is
0.104
±
0.017
nb
. The cross sections for electroproduction with
Q
2<1
GeV
2
and photoproduction are derived from the data and found to be
σ(ep→eb
b
̄
X)=7.1±0.6
(stat.)
+1.5
−1.3
(syst.)
nb
and
σ(γp→b
b
̄
X)=111
±
10
(stat.)
+23
−20
(syst.)
nb
at an average
〈W
γp〉∼180
GeV
, respectively.
Tobacco Use and Cryptogenic Stroke in Young Adults Jaffre, Aude, MD; Ruidavets, Jean Bernard, MD, PhD; Nasr, Nathalie, MD, PhD ...
Journal of stroke and cerebrovascular diseases,
12/2015, Letnik:
24, Številka:
12
Journal Article
Recenzirano
Objective: Cryptogenic stroke is the leading subtype of ischemic stroke in the young. We sought to evaluate the association between traditional cardiovascular risk factors and cryptogenic stroke by ...using a case–control study. Methods: Patients aged 18-54 years, consecutively treated for first-ever cryptogenic ischemic stroke in an academic stroke unit, were compared with subjects from the general population living in the same geographic area. Control subjects were matched for age and sex with patients. We further evaluated the association between significant risk factors and nonobstructive (<50% stenosis) carotid plaque and thrombus among patients with cryptogenic stroke. Odds ratios OR were calculated using logistic regression analysis. Results: A total of 155 patients with cryptogenic stroke (66.4% men, mean age 43.5 years SD 8.4) were included in the study. Cryptogenic stroke was associated with current tobacco use (42.6% in patients versus 23.9% in control subjects; OR = 2.38, 95% confidence interval CI 1.40-4.05, P = .002). Current tobacco use was associated with nonobstructive carotid plaque (OR = 6.22; 95% CI, 2.43-15.9; P = .001) and nonobstructive carotid thrombus (OR = 13.7; 95% CI, 1.42-132.7; P = .03) among the patients. Conclusion: Our case–control study showed a strong link between current tobacco use and cryptogenic stroke in young adults.
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