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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Azimuthal correlations for inclusive 2-jet, 3-jet, and 4-jet events in pp collisions at $\sqrt{s}= $ 13 TeV

Azimuthal correlations between the two jets with the largest transverse momenta $p_{\mathrm {T}}$ in inclusive 2-, 3-, and 4-jet events are presented for several regions of the leading jet $p_{\mathrm {T}}$ up to 4 $\,\text {Te}\text {V}$ . For 3- and 4-jet scenarios, measurements of the minimum azimuthal angles between any two of the three or four leading $p_{\mathrm {T}}$ jets are also presented. The analysis is based on data from proton–proton collisions collected by the CMS Collaboration at a centre-of-mass energy of 13 $\,\text {Te}\text {V}$ , corresponding to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ . Calculations based on leading-order matrix elements supplemented with parton showering and hadronization do not fully describe the data, so next-to-leading-order calculations matched with parton shower and hadronization models are needed to better describe the measured distributions. Furthermore, we show that azimuthal jet correlations are sensitive to details of the parton showering, hadronization, and multiparton interactions. A next-to-leading-order calculation matched with parton showers in the MC@NLO method, as implemented in herwig 7, gives a better overall description of the measurements than the powheg method.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Numerical and Experimental Study of an Aircraft Igniter Plasma Jet Discharge

The spark discharge of an aircraft plasma jet igniter is studied using high-fidelity numerical simulations and X-ray radiography measurements. The target problem here features the thermal expansion of hot gas introduced by the electric spark within a confined igniter cavity, which eventually evolves into a pulsed jet of a high-temperature kernel. A comprehensive set of models adapted from existing strategies for internal combustion engine spark plug discharge is extended to the target problem, including the modeling of energy deposition, plasma reactions, thermodynamic properties, and heat losses. A series of validation and parameter studies are performed and presented. The kernel size is found to be sensitive to heat losses arising from radiation and hot gas remained within the discharge cavity, rather than heat conduction to the wall in the discharge cavity. Depending on the enforced shape of the post-breakdown electric arc, the spark kernel can be off-centered, tilted, and considerably asymmetric. These features have been previously not considered when studying such igniter configurations and may have a first-order impact on the ignition process. Provided a proper setup of the heat loss models and electric arc shape, the numerical results are quantitatively comparable to the experimental results in terms of the kernel size, shape, and velocity throughout different stages after the spark discharge.

Tang, Yihao↗
NASA NTRS1946

Field of Flow About a Jet and Effect of Jets on Stability of Jet-Propelled Airplanes

A theoretical investigation was conducted on jet-induced flow deviation. Analysis is given of flow inclination induced outside cold and hot jets and jet deflection caused by angle of attack. Applications to computation of effects of jet on longitudinal stability and trim are explained. Effect of jet temperature on flow inclination was found small when thrust coefficient is used as criterion for similitude. The average jet-induced downwash over tail plane was obtained geometrically.

Ribner, Herbert S.↗
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

ATLAS $b$-jet identification performance and efficiency measurement with $t{\bar{t}}$ events in $pp$ collisions at $\sqrt{s}=13$

The algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the simulation and the efficiency with which these algorithms identify jets containing b-hadrons is measured in collision data. The measurement uses a likelihood-based method in a sample highly enriched in $t\bar{t}$ events. The topology of the t → Wb decays is exploited to simultaneously measure both the jet flavour composition of the sample and the efficiency in a transverse momentum range from 20 to 600 GeV. The efficiency measurement is subsequently compared with that predicted by the simulation. The data used in this measurement, corresponding to a total integrated luminosity of 80.5 fb -1 , were collected in proton–proton collisions during the years 2015–2017 at a centre-of-mass energy $ \sqrt{s}$ = 13 TeV. By simultaneously extracting both the efficiency and jet flavour composition, this measurement significantly improves the precision compared to previous results, with uncertainties ranging from 1 to 8% depending on the jet transverse momentum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurements of differential cross sections of top quark pair production in association with jets in pp collisions at $\sqrt{s}=13 $ TeV using the ATLAS detector

Measurements of differential cross sections of top quark pair production in association with jets by the ATLAS experiment at the LHC are presented. The measurements are performed as functions of the top quark transverse momentum, the transverse momentum of the top quark-antitop quark system and the out-of-plane transverse momentum using data from pp collisions at s√=13 TeV collected by the ATLAS detector at the LHC in 2015 and corresponding to an integrated luminosity of 3.2 fb -1 . The top quark pair events are selected in the lepton (electron or muon) + jets channel. The measured cross sections, which are compared to several predictions, allow a detailed study of top quark production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1993

Turbulence measurements in axisymmetric jets of air and helium. I - Air jet. II - Helium jet

Results are presented of measurements on turbulent round jets of air and of helium of the same nozzle momentum efflux, using, for the air jets, x-wire hot-wire probes mounted on a moving shuttle and, for He jets, a composite probe consisting of an interference probe of the Way-Libby type and an x-probe. Current models for scalar triple moments were evaluated. It was found that the performance of the model termed the Full model, which includes all terms except advection, was very good for both the air and the He jets.

Panchapakesan, N. R.↗
NASA NTRS1975

Analytical simulation of the far-field jet noise and the unsteady jet flow-field by a model of periodic shedding of vortex ring from the jet exit

The construction of a theoretical flow field due to shedding of vortex rings, the identification of the controlling parameters, and the determination of whether the theoretical model successfully simulated the unsteady pressure field near jet (and consequently the far field noise) was studied. The basic parameters contained in the analytic solutions were the epoch at which a vortex ring was shed near the jet exit and the eddy viscosity coefficient. These parameters were identified from the experimental data for the real-time pressure and from the spread of the mixing layer of the jet. Results of the theoretical analysis show good qualitative agreement with the experimental data.

Liu, C. H.↗