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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Top-down analysis of protein samples by de novo sequencing techniques

MOTIVATION: Recent technological advances have made high-resolution mass spectrometers affordable to many laboratories, thus boosting rapid development of top-down mass spectrometry, and implying a need in efficient methods for analyzing this kind of data. RESULTS: We describe a method for analysis of protein samples from top-down tandem mass spectrometry data, which capitalizes on de novo sequencing of fragments of the proteins present in the sample. Our algorithm takes as input a set of de novo amino acid strings derived from the given mass spectra using the recently proposed Twister approach, and combines them into aggregated strings endowed with offsets. The former typically constitute accurate sequence fragments of sufficiently well-represented proteins from the sample being analyzed, while the latter indicate their location in the protein sequence, and also bear information on post-translational modifications and fragmentation patterns.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Using spin alignment of inelastically excited nuclei in fast beams to assign spins: The spectroscopy of 13 O as a test case

Excited states in O 13 were investigated using inelastic scattering of an E / A = 69.5 MeV O 13 beam off of a Be 9 target. The excited states were identified in the invariant-mass spectra of the decay products. Both single-proton and sequential two-proton decays of the excited states were examined. Furthermore, for a number of the excited states, the protons were emitted with strong anisotropy where emissions transverse to the beam axis are favored. The measured proton-decay angular distributions were compared to predictions from distorted-wave Born-approximation calculations of the spin alignment which was shown to be largely independent of the excitation mechanism. The deduced O 13 level scheme is compared to ab initio no-core shell model with continuum predictions. The lowest-energy excited states decay isotropically consistent with predictions of strong proton 1 s 1 / 2 structure. Above these states in the level scheme, we observed a number of higher-spin states not predicted within the model. Possibly these are associated with rotational bands built on deformed cluster configurations predicted by antisymmetrized molecular dynamics calculations. The spin alignment mechanism is shown to be useful for making spin assignments and may have widespread use.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Faddeev-Chiral Unitary Approach to the $K^- d$ scattering length

Our earlier Faddeev three-body study in the $K^-$-deuteron scattering length, $A_{K^-d}$, is revisited here in the light of the recent developments in two fronts: {\it (i)} the improved chiral unitary approach to the theoretical description of the coupled $\Kbar N$ related channels at low energies, and {\it (ii)} the new and improved measurement from SIDDHARTA Collaboration of the strong interaction energy shift and width in the lowest $K^-$-hydrogen atomic level. Those two, in combination, have allowed us to produced a reliable two-body input to the three-body calculation. All available low-energy $K^-p$ observables are well reproduced and predictions for the $\Kbar N$ scattering lengths and amplitudes, $(\pi \Sigma)^\circ$ invariant-mass spectra, as well as for $A_{K^-d}$ are put forward and compared with results from other sources. The findings of the present work are expected to be useful in interpreting the forthcoming data from CLAS, HADES, LEPS and SIDDHARTA Collaborations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Double K S 0 photoproduction off the proton at CLAS

The $f_0$(1500) meson resonance is one of several contenders to have significant mixing with the lightest glueball. This resonance is well established from several previous experiments. Here we present the first photoproduction data for the $f_0$(1500) via decay into the $K_S^0 K_S^0$ channel using the CLAS detector. The reaction $\gamma p$ -> $f_0 p$ -> $K_S^0 K_S^0 p$, where J = 0, 2, was measured with photon energies from 2.7 to 5.1 GeV. A clear peak is seen at 1500 MeV in the background subtracted invariant mass spectra of the two kaons. This is enhanced if the measured 4-momentum transfer to the proton target is restricted to be less than 1.0 GeV2. By comparing data with simulations, it can be concluded that the peak at 1500 MeV is produced primarily at low t, which is consistent with a t-channel production mechanism.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Strangeness production via resonances in heavy-ion collisions at energies available at the GSI Schwerionensynchrotron

Production of strange hadrons in elementary and heavy-ion reactions is studied with the hadronic transport approach called simulating many accelerated strongly interacting hadrons. The poorly known branching ratios of the relevant hadronic resonances are constrained from the known elementary hadronic cross sections and from invariant mass spectra of dileptons. The constrained model is employed as a baseline to compare to heavy-ion-collision experiments at low energies [E kin = (1-2) A GeV] and to predict some of the upcoming pion-beam results at the High-Acceptance Di-Electron Spectrometer, which are expected to be sensitive to the resonance properties. The employed vacuum-resonance approach proves to be viable for small systems at these energies, but for large systems additional in-medium effects might be required.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Twist-2 pseudoscalar and vector meson distribution amplitudes in light-front quark model with exponential-type confining potential

We study the twist-2 distribution amplitudes (DAs) and the decay constants of pseudoscalar light ( π , K ) and heavy ( D , D s , B , B s ) mesons as well as the longitudinally and transversely polarized vector light ( ρ , K * ) and heavy ( D * , D s * , B * , B s * ) mesons in the light-front quark model with the Coulomb plus exponential-type confining potential V exp = a + b e α r in addition to the hyperfine interaction. We first compute the mass spectra of ground state pseudoscalar and vector light and heavy mesons and fix the model parameters necessary for the analysis, applying the variational principle with the trial wave function up to the first three lowest order harmonic oscillator (HO) wave functions $Φ(x,k_{\bot}) = Σ^{3}_{n=1} c_nΦ_{nS}$. We then obtain the numerical results for the corresponding decay constants of light and heavy mesons. We estimate the DAs, analyze their variation as a function of momentum fraction and compute the first six ξ -moments of the B and D mesons as well. We compare our results with the available experimental data as well as with the other theoretical model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Search for an exotic S = – 2 , Q = – 2 baryon resonance in proton-proton interactions at s N N = 17.3 GeV

Pentaquark states have been extensively investigated theoretically in the context of the constituent quark model. In this paper results of an experimental search for pentaquarks in the Ξ – π – , Ξ – π + , Ξ ¯ + π – and Ξ ¯ + π + invariant mass spectra in proton-proton interactions at s = 17.3 GeV are presented. Previous possible evidence from the NA49 collaboration of the existence of a narrow Ξ – π – baryon resonance in p + p interactions is not confirmed with almost 10 times greater event statistics. The search was performed using the NA61/SHINE detector which reuses the main components of the NA49 apparatus. No signal was observed with either the selection cuts of NA49 or newly optimized cuts.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Twist-3 generalized parton distribution for the proton from basis light-front quantization

We investigate the twist-3 generalized parton distributions (GPDs) for the valence quarks of the proton within the basis light-front quantization (BLFQ) framework. We first solve for the mass spectra and light-front waved functions (LFWFs) in the leading Fock sector using an effective Hamiltonian. Using the LFWFs we then calculate the twist-3 GPDs via the overlap representation. By taking the forward limit, we also get the twist-3 parton distribution functions (PDFs), and discuss their properties. Our prediction for the twist-3 scalar PDF agrees well with the CLAS experimental extractions.

Astronomy & Astrophysics↗
DOE OSTI2024

Observation of ψ ( 3686 ) → 3 ϕ

Using ( 2.712 ± 0.014 ) × 10 9 ψ ( 3686 ) events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of ψ ( 3686 ) → 3 ϕ decay with a significance larger than 10 σ . The branching fraction of this decay is determined to be ( 1.46 ± 0.05 ± 0.17 ) × 10 − 5 , where the first uncertainty is statistical and the second is systematic. No significant structure is observed in the ϕ ϕ invariant mass spectra. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2011

Search for new heavy particles decaying to ZZ→llll, lljj in pp̄ collisions at √s=1.96 TeV

We report on a search for anomalous production of Z boson pairs through a massive resonance decay in data corresponding to 2.5–2.9 fb⁻¹ of integrated luminosity in pp̄ collisions at √s=1.96 TeV using the CDF II detector at the Fermilab Tevatron. This analysis, with more data and channels where the Z bosons decay to muons or jets, supersedes the 1.1 fb⁻¹ four-electron channel result previously published by CDF. In order to maintain high efficiency for muons, we use a new forward tracking algorithm and muon identification requirements optimized for these high signal-to-background channels. Predicting the dominant backgrounds in each channel entirely from sideband data samples, we observe four-body invariant mass spectra above 300 GeV/c² that are consistent with background. We set limits using the acceptance for a massive graviton resonance that are 7–20 times stronger than the previously published direct limits on resonant ZZ diboson production.

Aaltonen, T.↗
DOE OSTI2016

125 GeV Higgs boson mass and muon g 2 in 5D MSSM

In the minimal supersymmetric standard model (MSSM), the tension between the observed Higgs boson mass and the experimental result of the muon g-2 measurement requires a large mass splitting between stops and smuons/charginos/neutralinos. Here, we consider a five-dimensional (5D) framework of the MSSM with the Randall-Sundrum warped background metric, and show that such a mass hierarchy is naturally achieved in terms of geometry. In our setup, the supersymmetry is broken at the ultraviolet (UV) brane, while all the MSSM multiplets reside in the 5D bulk. An appropriate choice of the bulk mass parameters for the MSSM matter multiplets can naturally realize the sparticle mass hierarchy desired to resolve the tension. Furthermore, the gravitino is localized at the UV brane and hence becomes very heavy, while the gauginos spreading over the bulk acquire their masses suppressed by the fifth dimensional volume. As a result, the lightest sparticle neutralino is a candidate for the dark matter as usual in the MSSM. In addition to reproducing the SM-like Higgs boson mass of around 125 GeV and the measured value of the muon g-2, we consider a variety of phenomenological constraints, and present the benchmark particle mass spectra that can be explored at the LHC Run-2 in the near future.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Doubly virtual ( π 0 , η , η ' ) → γ * γ * transition form factors in the light-front quark model

We report our investigation on the doubly virtual transition form factors (TFFs) F P γ * ( Q 1 2 , Q 2 2 ) for the P → γ * ( q 1 ) γ * ( q 2 ) ( P = π 0 , η , η ' ) transitions using the light-front quark model (LFQM). Performing a LF calculation in the exactly solvable manifestly covariant Bethe-Salpeter (BS) model as the first illustration, we use the q 1 + = 0 frame and find that both LF and manifestly covariant calculations produce exactly the same results for F P γ * ( Q 1 2 , Q 2 2 ) . This confirms the absence of the LF zero mode in the doubly virtual TFFs. We then map this covariant BS model to the standard LFQM using the more phenomenologically accessible Gaussian wave function provided by the LFQM analysis of meson mass spectra. For the numerical analyses of F P γ * ( Q 1 2 , Q 2 2 ) , we compare our LFQM results with the available experimental data and the perturbative QCD (pQCD) and vector meson dominance (VMD) model predictions. As ( Q 1 2 , Q 2 2 ) → ∞ , our LFQM result for doubly virtual TFF is consistent with the pQCD prediction, i.e., F P γ * ( Q 1 2 , Q 2 2 ) ~ 1 / ( Q 1 2 + Q 2 2 ) , while it differs greatly from the result of the VMD model, which behaves as F P γ * VMD ( Q 1 2 , Q 2 2 ) ~ 1 / ( Q 1 2 Q 2 2 ) . Our LFQM prediction for F η ' γ * ( Q 1 2 , Q 2 2 ) shows an agreement with the very recent experimental data obtained from the BABAR Collaboration for the ranges of 2 < ( Q 1 2 , Q 2 2 ) < 60 GeV 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Visualization of High Resolution Spatial Mass Spectrometric Data during Acquisition

Mass Spectrometric Imaging (IMS) allows the generation of 2D ion density maps that help visualize molecules present in sections of tissues and cells. The combination of spatial and mass resolution results in large and complex data sets that require powerful and efficient analysis and interpretation. In this paper, a graphical user interface (GUI) that can visualize the large data during data acquisition itself is presented. The program also has the ability to perform processing and analysis of the dataset. The various functions of the GUI including visualization of mass spectra, generation of 2D maps for selected species, manipulation of the heat maps, and peak identification are also presented.

Thomas, Mathew↗
DOE OSTI2013

Surface characterization of nanomaterials and nanoparticles: Important needs and challenging opportunities

This review examines characterization challenges inherently associated with understanding nanomaterials and the roles surface and interface characterization methods can play in meeting some of the challenges. In parts of the research community, there is growing recognition that studies and published reports on the properties and behaviors of nanomaterials often have reported inadequate or incomplete characterization. As a consequence, the true value of the data in these reports is, at best, uncertain. With the increasing importance of nanomaterials in fundamental research and technological applications, it is desirable that researchers from the wide variety of disciplines involved recognize the nature of these often unexpected challenges associated with reproducible synthesis and characterization of nanomaterials, including the difficulties of maintaining desired materials properties during handling and processing due to their dynamic nature. It is equally valuable for researchers to understand how characterization approaches (surface and otherwise) can help to minimize synthesis surprises and to determine how (and how quickly) materials and properties change in different environments. Appropriate application of traditional surface sensitive analysis methods (including x-ray photoelectron and Auger electron spectroscopies, scanning probe microscopy, and secondary ion mass spectroscopy) can provide information that helps address several of the analysis needs. In many circumstances, extensions of traditional data analysis can provide considerably more information than normally obtained from the data collected. Less common or evolving methods with surface selectivity (e.g., some variations of nuclear magnetic resonance, sum frequency generation, and low and medium energy ion scattering) can provide information about surfaces or interfaces in working environments (operando or in situ) or information not provided by more traditional methods. Although these methods may require instrumentation or expertise not generally available, they can be particularly useful in addressing specific questions, and examples of their use in nanomaterial research are presented.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Measurements of sputtered neutrals and ions and investigation of their roles on the plasma properties during rf magnetron sputtering of Zn and ZnO targets

Langmuir probe and optical absorption spectroscopy measurements were used to determine the line-integrated electron density, electron temperature, and number density of Ar atoms in metastable {sup 3}P{sub 2} and {sup 3}P{sub 0} levels in a 5 mTorr, rf magnetron sputtering plasmas used for the deposition of ZnO-based thin films. While the average electron energy and density of Ar atoms in {sup 3}P{sub 2} and {sup 3}P{sub 0} excited states were fairly independent of self-bias voltage, the Ar {sup 3}P{sub 2}-to-electron number density ratio decreased by approximately a factor of 5 when going from −115 V to −300 V. This decrease was correlated to an increase by about one order of magnitude of the number density of sputtered Zn atoms determined by absolute actinometry measurements on Zn I using either Ar or Xe as the actinometer gas. These results were also found to be in excellent agreement with the predictions of a global model accounting for Penning ionization of sputtered Zn particles. The importance of the latter reactions was further confirmed by plasma sampling mass spectrometry showing a double peak structure for Zn ions: a low-energy component ascribed to thermalized ions created in the gas phase (by direct electron impact and by Penning ionization) and a high-energy tail due to ions ejected from the target and reaching quasi-collisionlessly the substrate surface.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Chamber wall interactions with HBr/Cl{sub 2}/O{sub 2} plasmas

The authors have studied the interaction of HBr/Cl{sub 2}/O{sub 2} inductively coupled plasmas with reactor chamber wall deposits, with and without Si etching, using the “spinning wall” technique. The spinning wall is part of the reactor chamber walls, allowing near-real-time analysis of the composition of surface layers via Auger electron spectrometry and determination of species desorbing off the walls by mass spectrometry. In HBr plasmas with no bias voltage on the Si substrate, and hence no Si etching, HBr is ∼30% dissociated, and H{sub 2} and Br{sub 2} form in the plasma. Layers deposited on the reactor chamber contained little if any Br under these conditions. Adding O{sub 2} to an HBr plasma leads to formation of H{sub 2}O and increased Br{sub 2} (compared to a pure HBr plasma) products that desorb from the spinning wall. H{sub 2}O has a very long residence time on the surface. With bias voltage applied to the Si substrate in an HBr plasma, mass spectrometer signals are prominent for SiBr and SiBr{sub 3}, and weaker for SiBr{sub 2}, SiBr{sub 4}, Si{sub 2}Br{sub 4}, Si{sub 2}Br{sub 5}, and Si{sub 2}OBr{sub 5}. Under these conditions, a SiO{sub x}Br{sub y} layer deposits on the spinning wall. Adding 20% O{sub 2} to HBr stops etching and eliminates Br from the surface layer, indicating that Br on the reactor walls is a result of SiBr{sub x} impingement and not from bromination by impinging Br. With HBr/Cl{sub 2} plasmas and no bias on the stage, a SiO{sub x}Cl{sub y} layer deposits, and no Br is detected. HCl, BrCl, and Br{sub 2} were detected in the line-of-sight leak, around the spinning wall, of a HBr/Cl{sub 2} (1:1) gas mixture in the absence of a plasma. Residence time analysis of species in the chamber and a change in the product distribution with a change in the composition of the layer deposited on the chamber wall suggest that reactions forming these products in the absence of a plasma occur on the reactor walls. With a plasma and bias on the Si substrate, both Br and Cl incorporate in the layer, and a rich spectrum with numerous SiCl{sub x}Br{sub y} peaks was observed up to at least 500 amu. The spectrum does not change with the addition of 6% O{sub 2}. Adding 20% O{sub 2} suppresses Br adsorption, but Cl still adsorbs. In 40% O{sub 2}/HBr/Cl{sub 2} plasmas with stage bias, Cl adsorption also ceases and no etching products are observed in the mass spectrum.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗