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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Measurement of the asymmetry in angular distributions of leptons produced in dilepton t t ¯ final states in p p ¯ collisions at s = 1.96 TeV

We present measurements of asymmetries in angular distributions of leptons produced in ttbar events in proton-antiproton collisions at the Fermilab Tevatron Collider. We consider final states where the W bosons from top quark and antiquark decays both decay into l nu (l=e, mu) resulting in oppositely charged dilepton final states with accompanying jets. Using 9.7 fb -1 of integrated luminosity collected with the D0 detector, we find the asymmetries in lepton pseudorapidity compatible with predictions based on the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the direct C P -violating parameter A C P in the decay D + → K - π + π +

We measure the direct C P -violating parameter A C P for the decay of the charged charm meson, D + → K - π + π + (and charge conjugate), using the full 10.4 fb - 1 sample of p p ¯ collisions at s = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B → D processes) using input from Monte Carlo simulation. We measure A C P = [ - 0.16 ± 0.15 ( stat ) ± 0.09 ( syst ) ] % , which is consistent with zero, as expected from the standard model prediction of C P conservation, and is the most precise measurement of this quantity to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the ratio of inclusive cross sections $\sigma (p\bar{p} \rightarrow Z+2~b~\text{jets}) / \sigma (p\bar{p} \rightarrow Z+ \text{2 jets})$ in $p\bar{p}$ collisions at $\sqrt s=1.96$ TeV

In this study, we measure the ratio of cross sections, σ(pp¯ → Z + 2 b jets)/σ(pp¯ → Z + 2 jets), for associated production of a Z boson with at least two jets with transverse momentum p jet T > 20 GeV and pseudorapidity |η jet | < 2.5. This measurement uses data corresponding to an integrated luminosity of 9.7 fb –1 collected by the D0 experiment in Run II of Fermilab’s Tevatron pp¯ Collider at a center-of-mass energy of 1.96 TeV. The measured integrated ratio of 0.0236 ± 0.0032(stat) ± 0.0035(syst) is in agreement with predictions from next-to-leading-order perturbative QCD and the Monte Carlo event generators PYTHIA and ALPGEN .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from $t\bar t$ production at the Tevatron

We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in tt¯ production in dilepton final states using 9.7 fb –1 of proton-antiproton collisions at √s=1.96 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 tt¯ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of A tt¯ =(15.0±6.4(stat)±4.9(syst))% and a top-quark polarization times spin analyzing power in the beam basis of κP=(7.2±10.5(stat)±4.2(syst))%, with a correlation of –56% 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 κP=(11.3±9.1(stat)±1.9(syst))%. If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of A tt¯ =(17.5±5.6(stat)±3.1(syst))%. A combination with the D0 A tt¯ measurement in the lepton+jets final state yields an asymmetry of Att¯=(11.8±2.5(stat)±1.3(syst))%. Within their respective uncertainties, all these results are consistent with the standard model expectations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the Top Quark Mass Using the Matrix Element Technique in Dilepton Final States

We present a measurement of the top quark mass in pp¯ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb-1. The matrix element technique is applied to tt¯ events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of tt¯ decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt=173.93±1.84 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the W Boson Production Charge Asymmetry in p p ¯ → W + X → e ν + X Events at s = 1.96 TeV

We present a measurement of the W boson production charge asymmetry in p$\bar{p}$→W+X→eν+X events at a center of mass energy of 1.96 TeV, using 9.7 fb -1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined by using a neutrino weighting method, and the asymmetry is measured as a function of the W boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Implementation of an ultrasonic instrument for simultaneous mixture and flow analysis of binary gas systems

Precision ultrasonic measurements in binary gas systems provide continuous real-time monitoring of mixture composition and flow. Using custom micro-controller-based electronics, we have developed an ultrasonic instrument, with numerous potential applications, capable of making continuous high-precision sound velocity measurements. The instrument measures sound transit times along two opposite directions aligned parallel to - or obliquely crossing - the gas flow. The difference between the two measured times yields the gas flow rate while their average gives the sound velocity, which can be compared with a sound velocity vs. molar composition look-up table for the binary mixture at a given temperature and pressure. The look-up table may be generated from prior measurements in known mixtures of the two components, from theoretical calculations, or from a combination of the two. We describe the instrument and its performance within numerous applications in the ATLAS experiment at the CERN Large Hadron Collider (LHC). The instrument can be of interest in other areas where continuous in-situ binary gas analysis and flowmetry are required. (authors)

43 PARTICLE ACCELERATORS↗