59 research outputs found
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Search for scalar leptoquarks in the acoplanar jet topology in ppbar collisions at sqrt(s)=1.96 TeV
A search for leptoquarks has been performed in 310 pb-1 of data from ppbar
collisions at a center-of-mass energy of 1.96 TeV, collected by the D0 detector
at the Fermilab Tevatron Collider. The topology analyzed consists of acoplanar
jets with missing transverse energy. The data show good agreement with standard
model expectations, and a lower mass limit of 136 GeV has been set at the 95%
C.L. for a scalar leptoquark decaying exclusively into a quark and a neutrino.Comment: Minor changes in v2 to match the published version, 8 pages, 5
figure
Measurement of B(t->Wb)/B(t->Wq) at sqrt(s) = 1.96 TeV
We present the measurement of R = B(t->Wb)/B(t->Wq) in ppbar collisions at
sqrt(s) = 1.96 TeV, using 230 pb-1 of data collected by the DO experiment at
the Fermilab Tevatron Collider. We fit simultaneously R and the number of
selected top quark pairs (ttbar), to the number of identified b-quark jets in
events with one electron or one muon, three or more jets, and high transverse
energy imbalance. To improve sensitivity, kinematical properties of events with
no identified b-quark jets are included in the fit. We measure R = 1.03 +0.19
-0.17 (stat+syst), in good agreement with the standard model. We set lower
limits of R > 0.61 and |V_tb| > 0.78 at 95% confidence level.Comment: 7 pages, 1 figure submitted to Phys. Rev. Let
Search for the Standard Model Higgs Boson in the ZH --> neutrino-neutrino-b-b channel
We report a search for the standard model (SM) Higgs boson based on data
collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding
to an integrated luminosity of 260 pb^-1. We study events with missing
transverse energy and two acoplanar b-jets, which provide sensitivity to the ZH
production cross section in the neutrino-neutrino-b-b channel and to WH
production, when the lepton from the W -> lepton+neutrino decay is undetected.
The data are consistent with the SM background expectation, and we set 95% C.L.
upper limits on sigma(p p-bar -> ZH/WH) x B(H -> b b-bar) from 3.4/8.3 to
2.5/6.3 pb, for Higgs masses between 105 and 135 GeV.Comment: submitted to Phys. Rev. Letter
Semi-continuous PM2.5 inorganic composition measurements during the Pittsburgh air quality study
A method for semi-continuous (10 min time resolution) PM2.5 nitrate and sulfate measurements, based on the humidified impaction with flash volatilization design of Stolzenburg and Hering (Environ. Sci. Technol. 34 (2000) 907), was evaluated during the Pittsburgh Air Quality Study (PAQS) from July 2001 to August 2002. The semi-continuous measurements were corrected for several operating parameters. The overall corrections were less than 10% on average, but could be quite large for individual 10 min measurements. These corrections resulted in an improvement in the agreement of the measurements with the filter-based measurements, with a major axis regression relationship of y = 0.83x + 0.20 mug m(-3) and R-2 of 0.84 for nitrate and y = 0.71x + 0.42 mug m(-3) and R-2 of 0.83 for sulfate. The corrected semi-continuous measurements were calibrated over the entire year using collocated denuder/filter-pack-based measurements. These calibrated semi-continuous measurements are used in conjunction with temporally resolved gas-phase measurements of total (gas- and aerosol-phase) nitrate and meteorological measurements to investigate short-term phenomena at the Pittsburgh Supersite. The gas-to-particle partitioning of nitrate varied daily and seasonally, with a majority of the nitrate in the particle phase at night and during the winter months. (C) 2004 Elsevier Ltd. All rights reserved
Emerging adults' experiences of middle and high school sexual health education in New Brunswick, Nova Scotia, and Ontario
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