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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Search for low-scale gravity signatures in multi-jet final states with the ATLAS detector at $\sqrt{s}=8 $ TeV

A search for evidence of physics beyond the Standard Model in final states with multiple high-transverse-momentum jets is performed using 20.3 fb -1 of proton-proton collision data at √s = 8 TeV recorded by the ATLAS detector at the LHC. No significant excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross sections for non-Standard Model production of multi-jet final states are set. A wide variety of models for black hole and string ball production and decay are considered, and the upper limit on the cross section times acceptance is as low as 0.16 fb at the 95% confidence level. For these models, excluded regions are also given as function of the main model parameters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Measurement of the cross section for $\text{t}\bar{\text{t}}$ production with additional jets and b jets in pp collisions at $\sqrt{s}=$ 13 TeV

Measurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks $ \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}}\right) $ and in association with a pair of jets from quarks of any flavor or gluons $ \left({\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}}\right) $ and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb$^{−1}$. The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately for the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results of the measurements in the fiducial phase space for the dilepton and lepton+jets channels, respectively, are $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} $ = 2.36±0.02 (stat)±0.20 (syst) pb and 31.0±0.2 (stat)±2.9 (syst) pb, and for the cross section ratio 0.017 ± 0.001 (stat) ± 0.001 (syst) and 0.020 ± 0.001 (stat) ± 0.001 (syst). The values of $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{b}\overline{\mathrm{b}}} $ are determined from the product of the $ {\sigma}_{\mathrm{t}\overline{\mathrm{t}}\mathrm{jj}} $ and the cross section ratio, obtaining, respectively, 0.040±0.002 (stat)±0.005 (syst) pb and 0.62±0.03 (stat)±0.07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for pair production of heavy vector-like quarks decaying into high-p T W bosons and top quarks in the lepton-plus-jets final state in pp collisions at $ \sqrt{s}=13$ TeV with the ATLAS detector

A search is presented for the pair production of heavy vector-like B quarks, primarily targeting B quark decays into a W boson and a top quark. The search is based on 36.1 fb -1 of pp collisions at s√=13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, and multiple jets, of which at least one is b-tagged. No significant deviation from the Standard Model expectation is observed. The 95% confidence level lower limit on the B mass is 1350 GeV assuming a 100% branching ratio to Wt. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. The 100% branching ratio limits are found to be also applicable to heavy vector-like X production, with charge +5/3, that decay into Wt. In conclusion, this search is also sensitive to a heavy vector-like B quark decaying into other final states (Zb and Hb) and thus mass limits on B production are set as a function of the decay branching ratios.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at $ \sqrt{s}=8 $ TeV with the ATLAS detector

Several models of physics beyond the Standard Model predict neutral particles that decay into final states consisting of collimated jets of light leptons and hadrons (so-called “lepton jets”). These particles can also be long-lived with decay length comparable to, or even larger than, the LHC detectors’ linear dimensions. This paper presents the results of a search for lepton jets in proton-proton collisions at the centre-of-mass energy of $ \sqrt{s}=8 $ TeV in a sample of 20.3 fb collected during 2012 with the ATLAS detector at the LHC. Limits on models predicting Higgs boson decays to neutral long-lived lepton jets are derived as a function of the particle’s proper decay length.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Cost-effective valorization of 2,3-butanediol to high-value chemicals and jet fuel

Here, this work outlines an optimized process for converting 2,3-butanediol (BDO) into sustainable aviation fuel (SAF) and C4 chemicals. BDO is reactively separated from fermentation broth by forming dioxolanes, which are converted to isobutyraldehyde, methyl ethyl ketone (MEK), and 1,3-butadiene. These intermediates are reduced and dehydrated over Cu/ZSM-5 to form alkenes, which can be oligomerized and hydrotreated to jet-range alkanes. Previous BDO-dioxolane-alkene processes are limited by the requirement for a continuous aldehyde source for dioxolane formation. Brønsted acidic zeolites catalyze dioxolane deacetalization to form isobutyraldehyde and MEK in a >2:1 molar ratio, providing an internal, recyclable aldehyde source. Dioxolane formation optimization was performed to achieve >95% dioxolane yields over Amberlyst-15 and minimize isobutyraldehyde recycle. The overall BDO-dioxolane-fuel process yields an alkane mixture that enables at least a 50% v/v blend with Jet-A. Techno-economic analyses and life cycle assessments for this BDO-dioxolane-fuel process yield scenarios with <$2.50 per gallon gas equivalent and >58% reduction in CO2 emissions.

2,3-butanediol↗
DOE OSTI2015

Optical detection of the Pictor A jet and tidal tail: Evidence against an IC/CMB JET

New images of the FR II radio galaxy Pictor A from the Hubble Space Telescope reveal a previously undiscovered tidal tail, as well as a number of jet knots coinciding with a known X-ray and radio jet. The tidal tail is approximately 5″ wide (3 kpc projected), starting 18″ (12 kpc) from the center of Pictor A, and extends more than 90″ (60 kpc). The knots are part of a jet observed to be about 4′ (160 kpc) long, extending to a bright hotspot. These images are the first optical detections of this jet, and by extracting knot flux densities through three filters, we set constraints on emission models. While the radio and optical flux densities are usually explained by synchrotron emission, there are several emission mechanisms that might be used to explain the X-ray flux densities. Our data rule out Doppler-boosted inverse Compton scattering as a source of the high-energy emission. Instead, we find that the observed emission can be well described by synchrotron emission from electrons with a low-energy index (p∼2) that dominates the radio band, while a high-energy index (p∼3) is needed for the X-ray band and the transition occurs in the optical/infrared band. This model is consistent with a continuous electron injection scenario.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Penetration of Ar and He RF-driven plasma jets into micrometer-sized capillary tubes

The penetration and propagation of cold atmospheric pressure plasmas into volumes having sub-millimeter to micrometer sizes with large aspect ratios is required for enabling an effective disinfection of the inside of catheter tubes, tooth cavities, skin pores and enhance plasma catalysis in porous catalysts. Here, we report on a study using a low voltage RF driven argon and helium plasma jets with the plasma generation outside a capillary tube with a large aspect ratio followed by its penetration and propagation inside the capillary. We present the experimental determination of the limitations on the penetration diameter, and the underpinning mechanisms of the plasma propagation and penetration process. Experimental results include time resolved imaging of plasma propagation and penetration in capillaries with different internal diameter and surface electric field measurements. We found that the time between the plasma jet in first contact with the capillary tube surface and the subsequent penetration into the capillary tube spans several RF cycles due to electric fields at the plasma-tube interface below 4 kV cm –1 . These low electric fields require Penning ionization and/or stepwise ionization and hence a buildup of the metastable and electron density is required to achieve a sufficiently large ionization rate near the capillary tube inlet to enable penetration and propagation. Furthermore, it is found that the propagation of the argon jet into the capillary occurs during the positive half cycle of the RF waveform and is very similar to the propagation of the jet in surrounding air.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Effect of plasma on gas flow and air concentration in the effluent of a pulsed cold atmospheric pressure helium plasma jet

In this work, we report on the flow effects induced by a nanosecond pulsed helium cold atmospheric pressure plasma jet impinging on a glass substrate. Herein, gas temperature measurements have been performed using optical emission spectroscopy including rotational spectra of OH(A-X) (0,0) and N 2 (C-B) (0,0) and resonance broadening of a helium emission line at 667.8 nm. The measured increase in gas temperature was less than 15 K. We have measured the air concentration distribution in the jet effluent by means of Rayleigh scattering exploiting the large difference in Rayleigh cross-section of air and helium. The obtained results show that the plasma causes a broadening of the helium channel suggesting an enhanced gas velocity and mixing with the ambient air. The impact of the plasma on the jet effluent is polarity dependent and is larger in the case of positive applied voltage pulses. Using an estimation of the increased gas velocity required to obtain the observed air concentrations, we have shown that both gas heating and electrohydrodynamic (EHD) forces related to the propagation of an ionization front are not causing the observed phenomena. The surface charge which can exist for a much longer time than the duration of the applied voltage pulse is the primary cause of the EHD forces on the bulk charges which lead to significant different air concentration profiles in the jet effluent for plasma on and off.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Search for low-mass resonances decaying into two jets and produced in association with a photon or a jet at √s = 13 TeV with the ATLAS detector

A search is performed for localized excesses in the low-mass dijet invariant mass distribution, targeting a hypothetical new particle decaying into two jets and produced in association with either a high transverse momentum photon or a jet. The search uses the full Run 2 data sample from LHC proton-proton collisions collected by the ATLAS experiment at a center-of-mass energy of 13 TeV during 2015–2018. Two variants of the search are presented for each type of initial-state radiation: one that makes no jet flavor requirements and one that requires both of the jets to have been identified as containing b-hadrons. No excess is observed relative to the Standard Model prediction, and the data are used to set upper limits on the production cross section for a benchmark Z' model and, separately, for generic, beyond the Standard Model scenarios which might produce a Gaussian-shaped contribution to dijet invariant mass distributions. The results extend the current constraints on dijet resonances to the mass range between 200 and 650 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of top quark polarization in t t ¯ lepton + jets final states

We present a measurement of top quark polarization in t ¯ t pair production in p ¯ p collisions at √ s = 1.96 TeV using data corresponding to 9.7 fb -1 of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the t ¯ t production plane. This is the first measurement of top quark polarization at the Tevatron using lepton + jet final states and the first measurement of the transverse polarization in t ¯ t production. The observed distributions are consistent with standard model predictions of nearly no polarization.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Higgs boson decay to light jets at the LHC

We study here the Higgs boson $(h)$ decay to two light jets at the 14 TeV High-Luminosity-LHC (HL-LHC), where a light jet ($j$) represents any non-flavor tagged jet from the observational point of view. The decay mode $h\to gg$ is chosen as the benchmark since it is the dominant channel in the Standard Model (SM), but the bound obtained is further applicable to the light quarks $(j=u,d,s)$. We also estimate the achievable bounds on the decay branching fractions through the associated production $Vh\ (V=W^\pm,Z)$. Events of the Higgs boson decaying into heavy (tagged) or light (un-tagged) jets are correlatively analyzed. We find that with 3000 fb$^{-1}$ data at the HL-LHC, we should expect approximately $1\sigma$ statistical significance on the SM $Vh(gg)$ signal in this channel. This corresponds to a reachable upper bound ${\rm BR}(h\to jj) \leq 4~ {\rm BR}^{SM}(h\to gg)$ at $95\%$ confidence level. A consistency fit also leads to an upper bound ${\rm BR}(h\to cc) < 15~ {\rm BR}^{SM}(h\to cc)$ at $95\%$ confidence level. The estimated bound may be further strengthened by adopting multiple variable analyses, or adding other production channels.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Z-boson production in association with a jet at next-to-next-to-leading order in perturbative QCD

Here, we present the first complete calculation of Z-boson production in association with a jet in hadronic collisions through next-to-next-to-leading order in perturbative QCD. Our computation uses the recently proposed N-jettiness subtraction scheme to regulate the infrared divergences that appear in the real-emission contributions. We present phenomenological results for 13 TeV proton-proton collisions with fully realistic fiducial cuts on the final-state particles. The remaining theoretical uncertainties after the inclusion of our calculations are at the percent level, making the Z+jet channel ready for precision studies at the LHC run II.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the underlying event in jet events from 7 TeV proton–proton collisions with the ATLAS detector

Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on 37 pb -1 of proton–proton collision data collected at a centre-of-mass energy of 7 TeV. Charged-particle mean p T and densities of all-particle E T and charged-particle multiplicity and p T have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 to 800 GeV. The correlation of charged-particle mean p T with charged-particle multiplicity is also studied, and the E T densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurements of jet vetoes and azimuthal decorrelations in dijet events produced in pp collisions at √s = 7 TeV using the ATLAS detector

In addition jet activity in dijet events is measured using pp collisions at ATLAS at a centre-of-mass energy of 7TeV, for jets reconstructed using the anti-k t algorithm with radius parameter R=0.6. This is done using variables such as the fraction of dijet events without an additional jet in the rapidity interval bounded by the dijet subsystem and correlations between the azimuthal angles of the dijet s. They are presented, both with and without a veto on additional jet activity in the rapidity interval, as a function of the scalar average of the transverse momenta of the dijet s and of the rapidity interval size. The double differential dijet cross section is also measured as a function of the interval size and the azimuthal angle between the dijet s. These variables probe differences in the approach to resummation of large logarithms when performing QCD calculations. The data are compared to POWERHEG , interfaced to the PYTHIA 8 and HERWIG parton shower generators, as well as to HEJ with and without interfacing it to the ARIADNE parton shower generator. None of the theoretical predictions agree with the data across the full phase-space considered; however, POWERHEG + PYTHIA 8 and HEJ + ARIADNE are found to provide the best agreement with the data. These measurements use the full data sample collected with the ATLAS detector in 7TeV pp collisions at the LHC and correspond to integrated luminosities of 36.1pb –1 and 4.5fb –1 for data collected during 2010 and 2011, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector

A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb –1 of proton–proton collision data at √s = 7 TeV from 2010 and 0.1 nb –1 of data at √s = 8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of Geant4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2–5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of $WW/WZ \rightarrow \ell \nu q q^{\prime }$ production with the hadronically decaying boson reconstructed as one or two jets in $pp$ collisions at $\sqrt{s} =8~\text {TeV}$ with ATLAS, and constraints on anomalous gauge couplings

This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to e? or µv and one W or Z boson decaying hadronically. The analysis uses 20.2fb -1 of s=8TeVpp collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for WW / WZ production are measured in high-p T fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗