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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Measurement of the differential cross sections for isolated direct photon pair production in $p\bar{p}$ collisions at $\sqrt{s}$= 1.96 TeV

We present measurements of direct photon pair production cross sections using 8.5fb -1 of data collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ collider. The results are presented as differential distributions of the photon pair invariant mass $dσ/dM_{γγ}$, pair transverse momentum $dσ/dp^{γγ}_{T}$, azimuthal angle between the photons $dσ/dΔφ_{γγ}$, and polar scattering angle in the Collins–Soper frame $dσ/d|cos θ*|$. Measurements are performed for isolated photons with transverse momenta $p^γ_T$ > 18(17)GeV for the leading (next-to-leading) photon in $p_T$, pseudorapidities , |$η^γ$| < 0.9 and a separation in η–φ space Δ$\mathscr{R}_{γγ}$ >0.4. We present comparisons with the predictions from Monte Carlo event generators DIPHOX and RESBOS implementing QCD calculations at next-to-leading order, 2γNNLO at next-to-next-to-leading order, and SHERPA using matrix elements with higher-order real emissions matched to parton shower.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Cross section measurements at LANSCE for defense, science and applications

The Los Alamos Neutron Science Center (LANSCE) has three neutron sources that are used for nuclear science measurements. These sources are driven by an 800 MeV proton linear accelerator and cover an energy range from sub-thermal to hundreds of MeV. Research at the facilities is performed under the auspices of a US DOE user program under which research proposals are rated for merit by a program advisory committee and are scheduled based on merit and availability of beam time. A wide variety of instruments is operated at the neutron flight paths at LANSCE including neutron detector arrays, gamma-ray detector arrays, fission fragment detectors, and charged particle detectors. These instruments provide nuclear data for multiple uses that range from increasing knowledge in fundamental science to satisfying data needs for diverse applications such as nuclear energy, global security, and industrial applications. In addition, highlights of recent research related to cross sections measurements are presented, and future research initiatives are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Preface: Special Topic Section on Advanced Electronic Structure Methods for Solids and Surfaces

This Special Topic section on Advanced Electronic Structure Methods for Solids and Surfaces contains a collection of research papers that showcase recent advances in the high accuracy prediction of materials and surface properties. It provides a timely snapshot of a growing field that is of broad importance to chemistry, physics, and materials science.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Measurement of the ratio of differential cross sections σ(pp̄→Z+b jet)/σ(pp̄→Z+jet) in pp̄ collisions at √s=1.96 TeV

We measure the ratio of cross sections, σ(pp̄→Z+b jet)/σ(pp̄→Z+jet), for associated production of a Z boson with at least one jet. The ratio is also measured as a function of the Z boson transverse momentum, jet transverse momentum, jet pseudorapidity, and the azimuthal angle between the Z boson with respect to the highest p T b tagged jet. These measurements use data collected by the D0 experiment in Run II of Fermilab’s Tevatron pp̄ Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of 9.7 fb⁻¹. The results are compared to predictions from next-to-leading order calculations and various Monte Carlo event generators.

Abazov, V. M.↗
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 OSTI2019

Infrared absorption cross section of SiN x thin films

At the molecular level, resonant coupling of infrared radiation with oscillations of the electric dipole moment determines the absorption cross section, $σ$. The parameter σ relates the bond density to the total integrated absorption. In this work, $σ$ was measured for the Si–N asymmetric stretch mode in SiN x thin films of varying composition and thickness. Thin films were deposited by low pressure chemical vapor deposition at 850 °C from mixtures of dichlorosilane and ammonia. σ for each film was determined from Fourier transform infrared spectroscopy and ellipsometric measurements. Increasing the silicon content from 0% to 25% volume fraction amorphous silicon led to increased optical absorption and a corresponding systematic increase in σ from 4.77 × 10 –20 to 6.95 × 10 –20 cm 2 , which is consistent with literature values. The authors believe that this trend is related to charge transfer induced structural changes in the basal SiN x tetrahedron as the volume fraction of amorphous silicon increases. Furthermore, experimental $σ$ values were used to calculate the effective dipole oscillating charge, q, for four films of varying composition. The authors find that q increases with increasing amorphous silicon content, indicating that compositional factors contribute to modulation of the Si–N dipole moment. Additionally, in the composition range investigated, the authors found that $σ$ agrees favorably with trends observed in films deposited by plasma enhanced chemical vapor deposition.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector

The inclusive top quark pair (tt¯) production cross-section σ tt¯ has been measured in proton–proton collisions at √s = 7 TeV √s = 8 TeV with the ATLAS experiment at the LHC, using tt¯ events with an opposite-charge eμ pair in the final state. Thus, the measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb –1 and the 2012 8 TeV dataset of 20.3 fb –1 . The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σ tt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimizing the associated systematic uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the differential cross-sections of prompt and non-prompt production of J / ψ and ψ (2S) in pp collisions at √s = 7 and 8 TeV with the ATLAS detector

The production rates of prompt and non-prompt J/ψ and ψ(2S) mesons in their dimuon decay modes are measured using 2.1 and 11.4 fb -1 of data collected with the ATLAS experiment at the Large Hadron Collider, in proton–proton collisions at √s=7 and 8 respectively. Production cross-sections for prompt as well as non-prompt sources, ratios of ψ(2S) to J/ψ production, and the fractions of non-prompt production for J/ψ and ψ(2S) are measured as a function of meson transverse momentum and rapidity. Lastly, the measurements are compared to theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of top-quark pair differential cross-sections in the lepton+jets channel in pp collisions at $\sqrt{s}=8\,~{\mathrm {TeV}}$ using the ATLAS detector

Measurements of normalized differential cross-sections of top-quark pair production are presented as a function of the top-quark, t$\bar{t}$ system and event-level kinematic observables in proton–proton collisions at a centre-of-mass energy of √s=8TeV. The observables have been chosen to emphasize the t$\bar{t}$ production process and to be sensitive to effects of initial- and final-state radiation, to the different parton distribution functions, and to non-resonant processes and higher-order corrections. The dataset corresponds to an integrated luminosity of 20.3 fb - 1 , recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations. The results are in fair agreement with the predictions over a wide kinematic range. Nevertheless, most generators predict a harder top-quark transverse momentum distribution at high values than what is observed in the data. Predictions beyond NLO accuracy improve the agreement with data at high top-quark transverse momenta. Using the current settings and parton distribution functions, the rapidity distributions are not well modelled by any generator under consideration. However, the level of agreement is improved when more recent sets of parton distribution functions are used.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Searches for scalar leptoquarks and differential cross-section measurements in dilepton–dijet events in proton–proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV with the ATLAS experiment

Searches for scalar leptoquarks pair-produced in proton–proton collisions at $\sqrt{s}$ =13 TeV at the Large Hadron Collider are performed by the ATLAS experiment. A data set corresponding to an integrated luminosity of 36.1 fb -1 is used. Final states containing two electrons or two muons and two or more jets are studied, as are states with one electron or muon, missing transverse momentum and two or more jets. No statistically significant excess above the Standard Model expectation is observed. The observed and expected lower limits on the leptoquark mass at 95% confidence level extend up to 1.29 TeV and 1.23 TeV for first- and second-generation leptoquarks, respectively, as postulated in the minimal Buchmüller–Rückl–Wyler model, assuming a branching ratio into a charged lepton and a quark of 50%. In addition, measurements of particle-level fiducial and differential cross sections are presented for the Z→ ee, Z→ μμ and $ t\bar{t} $ processes in several regions related to the search control regions. Predictions from a range of generators are compared with the measurements, and good agreement is seen for many of the observables. However, the predictions for the Z→ ℓℓ measurements in observables sensitive to jet energies disagree with the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

Isoprene (C 5 H 8 , 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O 3 -initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600–6500 cm -1 region. The pressure-broadened (1 atmosphere N 2 ) spectra were recorded at 278, 298, and 323 K in a 19.94 cm path-length cell at 0.112 cm -1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.

Brauer, C. S.↗
NASA NTRS1972

Calculation of photoionization cross section near auto-ionizing lines and magnesium photoionization cross section near threshold

The research performed is briefly reviewed. A simple method was developed for the calculation of continuum states of atoms when autoionization is present. The method was employed to give the first theoretical cross section for beryllium and magnesium; the results indicate that the values used previously at threshold were sometimes seriously in error. These threshold values have potential applications in astrophysical abundance estimates.

Moore, E. N.↗
NASA NTRS1974

Reduction of acoustic disturbances in the test section of supersonic wind tunnels by laminarizing their nozzle and test section wall boundary layers by means of suction

The feasibility of quiet, suction laminarized, high Reynolds number (Re) supersonic wind tunnel nozzles was studied. According to nozzle wall boundary layer development and stability studies, relatively weak area suction can prevent amplified nozzle wall TS (Tollmien-Schlichting) boundary layer oscillations. Stronger suction is needed in and shortly upstream of the supersonic concave curvature nozzle area to avoid transition due to amplified TG (Taylor-Goertler) vortices. To control TG instability, moderately rapid and slow expansion nozzles require smaller total suction rates than rapid expansion nozzles, at the cost of larger nozzle length Re and increased TS disturbances. Test section mean flow irregularities can be minimized with suction through longitudinal or highly swept slots (swept behind local Mach cone) as well as finely perforated surfaces. Longitudinal slot suction is optimized when the suction-induced crossflow velocity increases linearly with surface distance from the slot attachment line toward the slot (through suitable slot geometry). Suction in supersonic blowdown tunnels may be operated by one or several individual vacuum spheres.

Pfenninger, W.↗
NASA NTRS1976

The Effects of Blowing Over Various Trailing-edge Flaps on an NACA 0006 Airfoil Section, Comparisons with Various Types of Flaps on other Airfoil Sections, and an Analysis of Flow and Power Relationships for Blowing Systems

The results are presented of a two-dimensional investigation conducted to determine the effect of blowing over various types of trailing-edge flaps on a wing having the NACA 0006 airfoil section and a drooped-nose flap. The position and profile of the trailing-edge flap, the nozzle height, and the location of the flap with respect to the nozzle were found to be important variables. Data from many investigations were used to make an evaluation of the effects of blowing on lift. An analysis was made of flow and power relationships for blowing systems.

Dods, J. B., Jr.↗