972 research outputs found
Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from production at the Tevatron
We present a simultaneous measurement of the forward-backward asymmetry and
the top-quark polarization in production in dilepton final states
using 9.7 fb of proton-antiproton collisions at TeV with
the D0 detector. To reconstruct the distributions of kinematic observables we
employ a matrix element technique that calculates the likelihood of the
possible kinematic configurations. After accounting for the presence
of background events and for calibration effects, we obtain a forward-backward
asymmetry of and a top-quark polarization times spin analyzing power in the beam
basis of ,
with a correlation of between the measurements. If we constrain the
forward-backward asymmetry to its expected standard model value, we obtain a
measurement of the top polarization of If we constrain the top polarization to its
expected standard model value, we measure a forward-backward asymmetry of
A
combination with the D0 measurement in the lepton+jets final
state yields an asymmetry of Within their respective uncertainties, all these
results are consistent with the standard model expectations.Comment: 16 pages, 16 figures, published versio
Inclusive production of the state in collisions at D0
We present a study of the inclusive production of the with the
decay to the final state in hadronic collisions. Based on
of collision data collected by the D0
experiment at the Fermilab Tevatron collider, we report the first evidence for
the prompt production of and find the fraction of events
originating from hadrons to be . The ratio of the non-prompt
production rate to the yield in the same channel is . The values of the
mass ~MeV
and width ~MeV are consistent with previous measurements. 8 pages, 2 figuesComment: Submitted to PRL. * pages, 2 figure
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
We measure the top quark mass in dilepton final states of top-antitop events
in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding
to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The
analysis features a comprehensive optimization of the neutrino weighting method
to minimize the statistical uncertainties. We also improve the calibration of
jet energies using the calibration determined in top-antitop to lepton+jets
events, which reduces the otherwise limiting systematic uncertainty from the
jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/-
0.85(syst) GeV.Comment: 10 pages, 2 figures, 2 tables, subm. to Phys. Lett.
The D0 Run IIb Luminosity Measurement
An assessment of the recorded integrated luminosity is presented for data
collected with the D0 detector at the Fermilab Tevatron Collider from June 2006
to September 2011 (Run IIb). In addition, a measurement of the effective cross
section for inelastic interactions, also referred to as the luminosity
constant, is reported. This measurement incorporates new features that lead to
a substantial improvement in the precision of the result. A luminosity constant
of \sigma_{LM} = 48.3\pm1.9\pm0.6 mb is obtained, where the first uncertainty
is due to the accuracy of the inelastic cross section used by both CDF and D0,
and the second uncertainty is due to D0 sources. The recorded luminosity for
the highest E_T jet trigger is L_rec = 9.2 \pm 0.4 fb^{-1}, with a relative
uncertainty of 4.3%.Comment: 20 pages, 23 figure
Combination of D0 measurements of the top quark mass
We present a combination of measurements of the top quark mass by the D0
experiment in the lepton+jets and dilepton channels. We use all the data
collected in Run I (1992--1996) at TeV and Run II (2001--2011) at
TeV of the Tevatron collider, corresponding to
integrated luminosities of 0.1 fb and 9.7 fb, respectively. The
combined result is: .Comment: 12 pages, 2 figure, published in Phys. Rev.
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of âs = 1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is Att(FB) = 0.128 ± 0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions
From colonial categories to local culture: Evolving state practices of ethnic enumeration in Oceania, 1965-2014
Numerous scholars have examined how governments in particular times and places have classified their populations by ethnicity, but studies that are both cross-national and longitudinal are rare. Using a unique database of census questionnaires, we examine state practices of ethnic enumeration over a 50-year period (1965â2014) in the 24 countries and areas that comprise Oceania. The regionâs extraordinary linguistic and cultural diversity, combined with its complex colonial history and indigenous politics, make it an ideal site for comparative analyses. We find a shift from biological conceptions of difference to a more cultural understanding of group identity, exemplified by a sharp rise in language questions and the decline of race-based inquiries. While local identity labels have largely displaced colonial categories, the imprimatur of previous regimes still lingers, particularly in Melanesia. These shifts in official constructions of ethnoracial differences reflect a gradual lessening of colonial influences on demographic practices
Journal Staff
We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and transverse momenta 30 < p(T)(gamma) < 200 GeV. The b-quark jets are required to have p(T)(jet) > 15 GeVand vertical bar y(jet)vertical bar < 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
Search for new fermions ("quirks") at the Fermilab Tevatron Collider
We report results of a search for particles with anomalously high ionization
in events with a high transverse energy jet and large missing transverse energy
in fb of integrated luminosity collected by the D0 experiment at
the Fermilab Tevatron collider. Production of such particles
(quirks) is expected in scenarios with extra QCD-like {\it SU(N)} sectors, and
this study is the first dedicated search for such signatures. We find no
evidence of a signal and set a lower mass limit of 107 ~GeV for the mass of a
charged quirk with strong dynamics scale in the range from 10 keV to
1 MeV.Comment: submitted to Phys. Rev. Letter
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