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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Neutrino constraints on inelastic dark matter after CDMS II results

We discuss the neutrino constraints from solar and terrestrial dark matter (DM) annihilations in the inelastic dark matter (iDM) scenario after the recent CDMS II results. To reconcile the DAMA/LIBRA data with constraints from all other direct experiments, the iDM needs to be light (m{sub {chi}}<100 GeV) and have a large DM-nucleon cross section ({sigma}{sub n{approx}}10{sup -4} pb in the spin-independent (SI) scattering and {sigma}{sub n{approx}}10 pb in the spin-dependent (SD) scattering). The dominant contribution to the iDM capture in the Sun is from scattering off Fe/Al in the SI/SD case. Current bounds from Super-Kamiokande exclude the hard DM annihilation channels, such as W{sup +}W{sup -}, ZZ, tt, and {tau}{sup +{tau}-}. For soft channels such as bb and cc, the limits are loose, but could be tested or further constrained by future IceCube plus DeepCore. For neutrino constraints from the DM annihilation in the Earth, due to the weaker gravitational effect of the Earth and inelastic capture condition, the constraint exists only for small mass splitting {delta}<40 keV and m{sub {chi}}{approx}(10,50) GeV even in the {tau}{sup +{tau}-} channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Diffractive Pion Dissociation into {pi}{sup -{pi}+{pi}-{pi}+{pi}-} at COMPASS

At the COMPASS experiment a sample of {approx}380000 exclusive events of diffractive pion dissociation on a lead target into a {pi}{sup -{pi}+{pi}-{pi}+{pi}-} final state has been recorded in 2004. The 5{pi} invariant mass spectrum shows a momentum transfer dependent structure peaking around 1.8 GeV/c{sup 2}. In the (4{pi}){sup 0} subsystem there is a clear signal for the f{sub 1}(1285) resonance decaying into 4 pions. In this note we describe the data sample and explore the physics potential of this final state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Interplay between electron-phonon interaction and Hubbard repulsion: Bipolaron formation

In the weak coupling limit, the 2D Hubbard model extended by on-site (local) and inter-site (long range) electron-phonon (EP) interaction has been investigated within Lanczos method of exact diagonalization (ED). On-site (S0) bipolaron formation has been favored by on-site EP interaction induced effective attraction between electrons. But, inter-site phonon mediated interaction between electrons helps to form both S0 and neighboring site (S1) bipolaron. It is further observed that both types of bipolaron formation are suppressed by on-site Hubbard repulsion.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Polycaprolactone: A Promising Addition to the Sequential Infiltration Synthesis Polymer Family Identified through In Situ Infrared Spectroscopy

Infiltration of inorganic oxides inside polymers using sequential infiltration synthesis (SIS) is an effective method for creating materials for a broad range of applications. The reactions between various polymer functional groups and organometallic/inorganic precursors are unique, which makes it essential to understand the specific interactions for a range of precursors and polymers to enable predictive process design and to extend the utility of SIS to applications. In this paper, in situ Fourier transform infrared spectroscopy (FTIR) measurements have been performed during Al 2 O 3 and TiO 2 SIS in three different homopolymers: poly(methyl methacrylate) (PMMA), poly(epsilon-caprolactone) (PCL), and poly(2-vinylpyridine) (P2VP). From the FTIR intensity changes after precursor exposure and during the subsequent purge times, it is demonstrated quantitatively that the interaction dynamics and the stability of the intermediate complexes of these polymers with the metal precursors are substantially different. A key finding from this comparative study is that PCL interacts far more strongly with metal precursors, even though its carbonyl (C=O) and ester (C-O-R) functional groups are similar to those of the more weakly interacting PMMA. This behavior suggests that additional factors beyond the identity of the functional groups dictate how polymers interact with metal compounds in SIS. PCL, which has not previously been reported in SIS processes, may be an attractive polymeric template for implementing SIS with improved uniformity and cost-effectiveness.

36 MATERIALS SCIENCE↗
NASA NTRS1981

The magnetic-anomaly model of the Jovian magnetosphere - A post-Voyager assessment

Predictions previously put forth (Dessler and Vasyliunas, 1979) as tests for the magnetic-anomaly model (in which the anomalously weak magnetic field region in the northern hemisphere of Jupiter influences the outer Jovian magnetosphere by one or more plasma interaction processes) are reexamined in the light of Voyager and other recent observations. With regard to the prediction of a restricted longitude range of enhanced interaction between Io and Jupiter's ionosphere, the longitudinal asymmetries seen both in ground-based observations of sulfur emissions from the Io torus and in Voyager observations of Jovian auroral emissions are found to agree well with the predicted asymmetries.

Vasyliunas, V. M.↗
DOE OSTI2022

Late-onset Circumstellar Medium Interactions are Rare: An Unbiased GALEX View of Type Ia Supernovae

Abstract Using ultraviolet (UV) light curves, we constrain the circumstellar environments of 1080 Type Ia supernovae (SNe Ia) within z < 0.5 from archival Galaxy Evolution Explorer (GALEX) observations. All SNe Ia are required to have pre- and post-explosion GALEX observations to ensure adequate subtraction of the host-galaxy flux. Using the late-time GALEX observations, we look for the UV excess expected from any interaction between the SN ejecta and circumstellar material (CSM). Four SNe Ia are detected near maximum light, and we compare the GALEX photometry to archival data. However, we find that none of our targets show convincing evidence of CSM interaction. A recent Hubble Space Telescope (HST) survey estimates that ∼6% of SNe Ia may interact with distant CSM, but statistical inferences are complicated by the small sample size and selection effects. By injecting model light curves into our data and then recovering them, we constrain a broad range of CSM interactions based on the CSM interaction start time and the maximum luminosity. Combining our GALEX nondetections with the HST results, we constrain occurrence of late-onset CSM interaction among SNe Ia with moderate CSM interaction, similar to that observed in PTF11kx, to f CSM ≲ 5.1% between 0 and 500 days after discovery and ≲2.7% between 500 and 1000 days after discovery at 90% confidence. For weaker CSM interactions similar to SN 2015cp, we obtain limits of ≲16% and ≲4.8%, respectively, for the same time ranges.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Polarization observables in {sup 2}H(e,e'p) at GeV energies

We discuss results for polarization observables in exclusive electron scattering from deuteron targets. In our relativistic calculation, we use the Gross equation to describe the nuclear ground state, and we use the SAID parametrization of the full nucleon-nucleon scattering amplitude for our description of the final state interactions. We show results for polarized deuteron targets and for polarized ejectile nucleons, and discuss the relevance of the different parts of the nucleon-nucleon scattering amplitude for the final state interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Substituent and Heteroatom Effects on π–π Interactions: Evidence That Parallel-Displaced π-Stacking is Not Driven by Quadrupolar Electrostatics

Stacking interactions are a recurring motif in supramolecular chemistry and biochemistry, where a persistent theme is a preference for parallel-displaced aromatic rings rather than face-to-face π-stacking. This is usually explained in terms of quadrupole–quadrupole interactions between the arene moieties but that interpretation is inconsistent with accurate calculations, which reveal that the quadrupolar picture is qualitatively wrong. At typical π-stacking distances, quadrupolar electrostatics may differ in sign from an exact calculation based on charge densities of the interacting arenes. We apply symmetry-adapted perturbation theory to dimers composed of substituted benzene and various aromatic heterocycles, which display a wide range of electrostatic interactions, and we investigate the interplay of Pauli repulsion, dispersion, and electrostatics as it pertains to parallel-displaced π-stacking. Profiles of energy components along cofacial slip-stacking coordinates support a prominent role for the “van der Waals model” (dispersion in competition with Pauli repulsion), even for polar monomers where electrostatic interactions are significant. While electrostatic interactions are necessary to explain the optimal face-to-face π-stacking distance and to account for the relative orientation of one polar arene with respect to another, we find no evidence to support continued invocation of quadrupolar electrostatics as a basis for π-stacking. Our results suggest that a driving force for offset-stacking exists even in the absence of electrostatic interactions. Consequently, tuning electrostatics via functionalization does not guarantee that slip-stacking can be avoided. This has implications for rational design of soft materials and other supramolecular architectures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Isospin dependence of Nucleon-Nucleon Short-range Correlations in Inclusive Scattering with Tritium and Helium-3

The nucleon-nucleon (NN) potential has a strong repulsive core. When a two-nucleon (sub)system falls into this range, they will interact strongly at short distance, and move away from each other with momenta above the Fermi level. This is called the NN Short range Correlations (SRCs). Previous experiments reported a neutron-proton pair (isos inglet) dominance in high-momentum nucleons. In inclusive electron scattering, this np dominance will cause a scaling behavior of cross sections at 1.4 < xbj = Q2/2m? < 2 where the high-momentum nucleons dominate. At Je?erson Lab Hall A we checked this hypothesis with electron Quasi-elastic (QE) scattering on A=3 nuclei systems. Our unique gas cell design made electron-tritium scattering possible for the ?rst time in a decade. The 2H, 3H, and 3He inclusive cross sections at 1 < xbj < 3 were measured in two experiments (E12-11-112 and E12-14-011) with a wide Q2 range (0.4 < Q2 < 3 GeV2). This thesis dis cusses the physics goals, experiment setup, and data analysis of the E12-11-112 experiment. Ratios of 3H/2H, 3He/2H and 3H/3He as well as absolute cross sections are presented at 0.4 < Q2 < 1.8 GeV2. NN SRC plateaus are observed in the cross section ratios at high Q2. The 3H/3He ratio of 0.84±0.01 at NN SRC dominant kinematics indicates a np to pp SRC pair ratio of 2.2±0.2 in A=3 nuclei. That implies a preference in T = 0 isospin singlet con?guration. No plateaus are observed at xbj > 2.

Li, Shujie↗
DOE OSTI2018

Laser Synthesis, Processing, and Spectroscopy of Atomically-Thin Two Dimensional Materials

Atomically-thin two-dimensional (2D) materials display widely varying electronic and vibronic properties compared to their bulk counterparts. Laser interactions with 2D materials are central to their development. Here we attempt to overview recent progress and define the current challenges in the broad range of laser interactions involved in the synthesis, processing, and optical characterization of 2D materials as the field has emerged from graphene and h-BN to encompass a multitude of other atomically-thin semiconducting, superconducting, thermoelectric, etc. 2D materials as “building blocks” for future energy applications and devices. Here, we first focus on challenges in the synthesis and processing of mainly semiconducting 2D layers for optoelectronics, and the advantages offered by non-equilibrium laser processing. Then, we review the optical characterization techniques that are being developed to serve as remote probes of their electronic and vibronic properties, as well as their structure, stacking, and atomistic alignment. Together, examples will be shown how these developments are already being merged to fulfill the promise for tailored synthesis and assembly of these exquisite materials with real-time in situ control of structure and optoelectronic properties.

Geohegan, David↗
DOE OSTI2015

PICASSO, COUPP and PICO - Search for dark matter with bubble chambers

The PICASSO and COUPP collaborations use superheated liquid detectors to search for cold dark matter through the direct detection of weakly interacting massive particles (WIMPs). These experiments, located in the underground laboratory of SNOLAB, Canada, detect phase transitions triggered by nuclear recoils in the keV range induced by interactions with WIMPs. We present details of the construction and operation of these detectors as well as the results, obtained by several years of observations. We also introduce PICO, a joint effort of the two collaborations to build a second generation ton-scale bubble chamber with 250 liters of active liquid.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

The Pierre Auger Project and Enhancements

The current status of the scientific results of the Auger Observatory will be discussed which include spectrum, anisotropy in arrival directions, chemical composition analyses, and limits on neutrino and photon fluxes. A review of the Observatory detection systems will be presented. Auger has started the construction of its second phase which encompasses antennae for radio detection of cosmic rays, high-elevation telescopes, and surface plus muon detectors. Details will be presented on the latter, AMIGA (Auger Muons and Infill for the Ground Array), an Auger project consisting of 85 detector pairs each one composed of a surface water-Cherenkov detector and a buried muon counter. The detector pairs are arranged in an array with spacings of 433 and 750 m in order to perform a detailed study of the 10{sup 17} eV to 10{sup 19} eV spectrum region. Preliminary results on the performance of the 750 m array of surface detectors and the first muon counter prototype will be presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Search for Strangeonia in Photoproduction using CLAS

The HyCLAS experiment at Jefferson Lab is a program to search for new and unusual mesons produced via photoproduction. The strangeonia sector is poorly known and a main component of this program is a search for new strangeonium states. The reaction {gamma}p{yields}p{phi}{eta} is an ideal channel to look for strangeonium states due to the strangeness content of both the {phi} and {eta}. The data was acquired at the JLAB CLAS facility using a 4-5.5 GeV tagged photon beam. The {phi} meson is identified via the K{sup +}K- decay. The recoil proton is observed in the CLAS spectrometer and the {eta} meson is identified through the missing mass. Also of interest is the search for strangeonia decaying to {phi}{pi}{sup 0} and {phi}{omega}. These channels are OZI suppressed for qq-bar mesons and an observation of a meson decaying to these channels would provide a strong evidence of mesons beyond qqa-bar. Preliminary results describing the data quality, kinematics and dynamics will be shown.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Measurements of the Polarization Observables I{sup s} and I{sup c} for {gamma}{sup {yields}p{yields}}p{pi}{sup +{pi}-} using the CLAS Spectrometer

Model predictions regarding the excited baryon spectrum provided by Constituent Quark Models show good agreement with experimental measurements in the low-energy region less than {approx_equal}1.8 GeV. The mass region above {approx_equal}1.8 GeV, however, contains many resonances which are predicted to exist by these models but have not been experimentally verified. The analysis of a double meson final state using linearly polarized photoproduction data allows access to two polarization observables, I{sup s} and I{sup c}(also known as the beam asymmetry {Sigma} for a single meson final state). It has been shown that measurements of these polarizaton observables can provide insight into this missing resonance problem. This analysis was carried out on data taken from the CLAS-g8b data run period conducted at Jefferson Lab in Newport News, Virginia. The analysis of this data and preliminary measurements of these obsevables will be dicussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

High-precision determination of the electric and magnetic form factors of the proton

New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to Q{sup 2} = (GeV/c){sup 2} with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be r{sub E}{sup 2} rpost={sup >>1/2} 0.879(5){sub stat.}(4){sub syst.}(2){sub model}(4){sub group}fm and r{sub M}{sup 2} {sup 1/2} = 0.777(13){sub stat.}(9){sub syst.}(5)model({sub 2})groupfm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

One-pion production in neutrino-nucleus collisions

We use our model for neutrino pion production on the nucleon to study pion production on a nucleus. The model is conveniently modified to include in-medium corrections and its validity is extended up to 2 GeV neutrino energies by the inclusion of new resonant contributions in the production process. Our results are compared with recent MiniBooNE data measured in mineral oil. Our total cross sections are below data for neutrino energies above ≈ 1 GeV. As with other theoretical calculations, the agreement with data improves if we neglect pion final state interaction. This is also the case for differential cross sections convoluted over the neutrino flux.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

The Glashow resonance at IceCube: signatures, event rates and pp vs. pγ interactions

We revisit the signatures of the Glashow resonance process ν-bar {sub e}e → W in the high-energy astrophysical neutrino observatory IceCube. We note that in addition to the standard hadronic and electromagnetic showers produced by an incoming neutrino at the resonance energy of E{sub ν} ≈ 6.3 PeV, there are two clear signals of the process: the 'pure muon' from ν-bar {sub e}e → ν-bar {sub μ}μ and the 'contained lollipop' from ν-bar {sub e}e → ν-bar {sub τ}τ. The event rate and the signal-to-background ratio (the ratio of the resonant to concurrent non-resonant processes) are calculated for each type of interaction, based on current flux limits on the diffuse neutrino flux. Because of the low background in the neighborhood of the resonance, the observation of only one pure muon or contained lollipop event essentially signals discovery of the resonance, even if the expected event numbers are small. We also evaluate the total event rates of the Glashow resonance from the extra-galactic diffuse neutrino flux and emphasize its utility as a discovery tool to enable first observations of such a flux. We find that one can expect 3.6 (0.65) events per year for a pure pp (pγ) source, along with an added contribution of 0.51 (0.21) from non-resonant events. We also give results as a function of the ratio of pp vs pγ sources.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗