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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Measurement of the isolated diphoton cross section in p p collisions at s = 7 TeV with the ATLAS detector

Here, the ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s = 7 TeV. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of 37 pb –1 . The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass (m γγ ), total transverse momentum (pT, γγ ), and azimuthal separation (ΔΦ γγ ), are presented and compared to the predictions of next-to-leading-order QCD.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Measurements of single top quark production cross sections and |V tb | in pp̄ collisions at √s=1.96 TeV

We present measurements of production cross sections of single top quarks in pp̄ collisions at √s=1.96 TeV in a data sample corresponding to an integrated luminosity of 5.4 fb⁻¹ collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of σ(pp̄→tb+X,tqb+X)=3.43± 0.73 0.74 pb and use it to extract the CKM matrix element 0.79<|V tb |≤1 at the 95% C.L. We also measure σ(pp̄→tb+X)=0.68±0.380.35 pb and σ(pp̄→tqb+X)=2.86± 0.69 0.63 pb when assuming, respectively, tqb and tb production rates as predicted by the standard model.

Abazov, V. M.↗
DOE OSTI2019

First measurement of elastic, inelastic and total cross-section at $$\sqrt{s}=13$$ s = 13 TeV by TOTEM and overview of cross-section data at LHC energies: TOTEM Collaboration

The TOTEM collaboration has measured the proton–proton total cross section at s√=13 TeV with a luminosity-independent method. Using dedicated β*=90 m beam optics, the Roman Pots were inserted very close to the beam. The inelastic scattering rate has been measured by the T1 and T2 telescopes during the same LHC fill. After applying the optical theorem the total proton–proton cross section is σ tot =(110.6 ± 3.4 ) mb, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections σ el =(31.0 ± 1.7) mb and σ inel =(79.5 ± 1.8) mb .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the Inelastic Proton-Proton Cross Section at s = 13 TeV with the ATLAS Detector at the LHC

This Letter presents a measurement of the inelastic proton-proton cross section using 60 μ b -1 of p p collisions at a center-of-mass energy √ s of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region ( 2.07 < | η | < 3.86 ) of the detector. A cross section of 68.1 ± 1.4 mb is measured in the fiducial region ξ = M $2\atop{X}$ / s > 10 - 6 , where M X is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with M X > 13 GeV . The measured cross section is compared with a range of theoretical predictions. When extrapolated to the full phase space, a cross section of 78.1 ± 2.9 mb is measured, consistent with the inelastic cross section increasing with center-of-mass energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of fiducial differential cross sections of gluon-fusion production of Higgs bosons decaying to WW *→eνμν with the ATLAS detector at s = 8 $$ \sqrt{s}=8 $$ TeV

This paper describes a measurement of fiducial and differential cross sections of gluon-fusion Higgs boson production in the H → W W*→ eνμν channel, using 20.3 fb -1 of proton-proton collision data. The data were produced at a centre-of-mass energy of √=8 TeV at the CERN Large Hadron Collider and recorded by the ATLAS detector in 2012. Cross sections are measured from the observed H→ W W*→ eνμν signal yield in categories distinguished by the number of associated jets. The total cross section is measured in a fiducial region defined by the kinematic properties of the charged leptons and neutrinos. Differential cross sections are reported as a function of the number of jets, the Higgs boson transverse momentum, the dilepton rapidity, and the transverse momentum of the leading jet. The jet-veto efficiency, or fraction of events with no jets above a given transverse momentum threshold, is also reported. All measurements are compared to QCD predictions from Monte Carlo generators and fixed-order calculations, and are in agreement with the Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Photoionization of Ne Atoms and Ne{sup +} Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

Single, double, and triple photoionization of Ne{sup +} ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon–ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV, facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne{sup +}(1s2s{sup 2}2p{sup 62}S{sub 1/2}) level, for example, requires cooperative interaction of at least four electrons.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Measurement of the prompt J /$\psi$ pair production cross-section in pp collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

The production of two prompt J/ψ mesons, each with transverse momenta p T > 8.5 GeV and rapidity |y| < 2.1, is studied using a sample of proton-proton collisions at $\sqrt{s} = 8$ TeV, corresponding to an integrated luminosity of 11.4 fb –1 collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised J/ψ production, is measured as a function of the transverse momentum of the lower-p T J/ψ meson, di-J/ψp T and mass, the difference in rapidity between the two J/ψ mesons, and the azimuthal angle between the two J/ψ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/ψ mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be σ eff = 6.3 ± 1.6(stat)±1.0(syst) mb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

PIXiE: an algorithm for automated ion mobility arrival time extraction and collision cross section calculation using global data association

Abstract Motivation Drift tube ion mobility spectrometry coupled with mass spectrometry (DTIMS-MS) is increasingly implemented in high throughput omics workflows, and new informatics approaches are necessary for processing the associated data. To automatically extract arrival times for molecules measured by DTIMS at multiple electric fields and compute their associated collisional cross sections (CCS), we created the PNNL Ion Mobility Cross Section Extractor (PIXiE). The primary application presented for this algorithm is the extraction of data that can then be used to create a reference library of experimental CCS values for use in high throughput omics analyses. Results We demonstrate the utility of this approach by automatically extracting arrival times and calculating the associated CCSs for a set of endogenous metabolites and xenobiotics. The PIXiE-generated CCS values were within error of those calculated using commercially available instrument vendor software. Availability and implementation PIXiE is an open-source tool, freely available on Github. The documentation, source code of the software, and a GUI can be found at https://github.com/PNNL-Comp-Mass-Spec/PIXiE and the source code of the backend workflow library used by PIXiE can be found at https://github.com/PNNL-Comp-Mass-Spec/IMS-Informed-Library. Supplementary information Supplementary data are available at Bioinformatics online.

Ma, Jian↗
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 OSTI2012

Rapidity gap cross sections measured with the ATLAS detector in pp collisions at $\sqrt{s} = 7 \mbox{~TeV}$

Pseudorapidity gap distributions in proton-proton collisions at s√=7 ~TeVs=7 ~TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 μb -1 . Cross sections are measured differentially in terms of Δη F , the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at η= ±4.9, in which no final state particles are produced above a transverse momentum threshold p$cut\atop{T}$ . The measurements span the region 0<Δη F < 8 for 200~MeV< p$cut\atop{T}$ <800~MeV200~MeV F , the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process (pp→Xp), enhanced by double dissociation (pp→XY) where the invariant mass of the lighter of the two dissociation systems satisfies M Y ≲7 GeV. The resulting cross section is dσ/dΔη F ≈1 mb for Δη F ≳3. The large rapidity gap data are used to constrain the value of the Pomeron intercept appropriate to triple Regge models of soft diffraction. Finally, the cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Measurement of the inclusive jet cross section in pp collisions at sqrt(s)=2.76 TeV and comparison to the inclusive jet cross section at sqrt(s)=7 TeV using the ATLAS detector

CERN-LHC. This paper reports the measurement of inclusive jet cross sections in proton-proton collisions at a centre-of-mass energy of 2.76 TeV using a data sample of integrated luminosity of 0.20 pb-1 collected in 2011. Jets are identified using the anti-kt algorithm with two radius parameters (0.4 and 0.6). The cross sections are presented as a function of the jet transverse momentum and rapidity covering jets from 20-430 GeV in transverse momentum and |rapidity| < 4.4. The data are also compared with previous ATLAS 7 TeV cross sections as functions of PT and XT. The main tables below show the results correlated and uncorrelated systematic errors individually combined, as presented in the plots in the paper. The first table below gives access to the complete tables with the various sources of systematic error individually presented. Correlations over the rapidity bins and to the 7 TeV data are shown in table 1 of the paper and repeated below.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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.↗