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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Amplitude analysis of D + → K S 0 π + π + π -

The decay D + → K S 0 π + π + π - is studied with an amplitude analysis using a data set of 2.93 fb - 1 of e + e - collisions at the ψ ( 3770 ) peak accumulated by the BESIII detector. Intermediate states and nonresonant components, and their relative fractions and phases, have been determined. The significant amplitudes, which contribute to the model that best fits the data, are composed of five quasitwo-body decays K S 0 a 1 ( 1260 ) + , K ¯ 1 ( 1270 ) 0 π + K ¯ 1 ( 1400 ) 0 π + , K ¯ 1 ( 1650 ) 0 π + , and K ¯ ( 1460 ) 0 π + , a three-body decay K S 0 π + ρ 0 , as well as a nonresonant component K S 0 π + π + π - . The dominant amplitude is K S 0 a 1 ( 1260 ) + , with a fit fraction of ( 40.3 ± 2.1 ± 2.9 ) % , where the first and second uncertainties are statistical and systematic, respectively.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Observation of the decay ψ ( 3686 ) → Σ 0 Σ ¯ 0 ω

Using a dataset of ( 27.12 ± 0.14 ) × 10 8 ψ ( 3686 ) events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of the decay ψ ( 3686 ) → Σ 0 Σ ¯ 0 ω with a statistical significance of 8.9 σ . The measured branching fraction is ( 1.24 ± 0.1 6 stat ± 0.1 1 sys ) × 10 − 5 , where the first uncertainty is statistical and the second is systematic. Additionally, we investigate potential intermediate states in the invariant mass distributions of Σ 0 ω , Σ ¯ 0 ω and Σ 0 Σ ¯ 0 . A hint of a resonance is observed in the invariant mass distribution of M Σ 0 ( Σ ¯ 0 ) ω , located around 2.06 GeV / c 2 , with a significance of 2.5 σ . Published by the American Physical Society 2025

Ablikim, M.↗
DOE OSTI2011

Constraints on dark matter models from a Fermi LAT search for high-energy cosmic-ray electrons from the Sun

During its first year of data taking, the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope has collected a large sample of high-energy cosmic-ray electrons and positrons (CREs). We present the results of a directional analysis of the CRE events, in which we searched for a flux excess correlated with the direction of the Sun. Two different and complementary analysis approaches were implemented, and neither yielded evidence of a significant CRE flux excess from the Sun. Here, we derive upper limits on the CRE flux from the Sun’s direction, and use these bounds to constrain two classes of dark matter models which predict a solar CRE flux: (1) models in which dark matter annihilates to CREs via a light intermediate state, and (2) inelastic dark matter models in which dark matter annihilates to CREs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Pascalutsa-Vanderhaeghen light-by-light sum rule from photon-photon collisions

Light-by-light scattering sumrules based on general field theory principles relate cross-sections with different helicities. In this paper the simplest sumrule is tested for the $I=0$ and $2$ channels for \lq\lq real'' photon-photon collisions. Important contributions come from the long-lived pseudoscalar mesons and from di-meson intermediate states. The latest Amplitude Analysis of $\gamma\gamma\to\pi\pi, \overline{K}K$ allows this contribution to be evaluated. Furthermore, we find that other multi-meson contributions up to 2.5~GeV are required to satisfy the sumrules. While data on three and four pion cross-sections exist, there is no information about their isospin and helicity decomposition. Nevertheless, we show the measured cross-sections are sufficiently large to ensure the sumrules for the helicity differences are likely fulfilled.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Path description of coordinate-space amplitudes

We develop a coordinate version of light-cone-ordered perturbation theory, for general time-ordered products of fields, by carrying out integrals over one light-cone coordinate for each interaction vertex. The resulting expressions depend on the lengths of paths, measured in the same light-cone coordinate. Each path is associated with a denominator equal to a “light-cone deficit,” analogous to the “energy deficits” of momentum-space time- or light-cone-ordered perturbation theory. In effect, the role played by intermediate states in momentum space is played by paths between external fields in coordinate space. We derive a class of identities satisfied by coordinate diagrams, from which their imaginary parts can be derived. Using scalar QED as an example, we show how the eikonal approximation arises naturally when the external points in a Green function approach the light cone, and we give applications to products of Wilson lines. Although much of our discussion is directed at massless fields in four dimensions, we extend the formalism to massive fields and dimensional regularization.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Radiative Corrections to Superallowed β Decays in Effective Field Theory

The accuracy of V u d determinations from superallowed β decays critically hinges on control over radiative corrections. Recently, substantial progress has been made on the single-nucleon, universal corrections, while nucleus-dependent effects, typically parametrized by a quantity δ NS , are much less well constrained. Here, we lay out a program to evaluate this correction from effective field theory (EFT), highlighting the dominant terms as predicted by the EFT power counting. Moreover, we compare the results to a dispersive representation of δ NS and show that the expected momentum scaling applies even in the case of low-lying intermediate states. Our EFT framework paves the way toward calculations of δ NS and thereby addresses the dominant uncertainty in V u d . Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Nature of polyamorphic transformations in H 2 O under isothermal compression and decompression

In this paper, we report polyamorphic transformations of H 2 O under isothermal compression and decompression at 150 K, observed by in situ x-ray diffraction. Detailed structural information across the transformations among low-, high-, and very high-density amorphs (LDA, HDA, VHDA) reveals the mechanisms, the reversibility, and (dis)continuity of the transformations. During isothermal (de)compression, the polyamorphic transformations are characterized by a sharp and reversible LDA-VHDA transformation, with an HDA-like form (referred to as HDA’) appearing as an intermediate state. The LDA-VHDA transformation is found to occur in two steps: a discontinuous transition between LDA and HDA’ and a continuous change within HDA’ involving structural reconfigurations and finally converging to VHDA. Both LDA and VHDA are found to be structurally stable showing elastic behavior under (de)compression, while HDA’ is structurally unstable. Lastly, possible relations of these observations to low- and high-density liquids are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Nonresonant two-photon x-ray absorption in Cu

We present a real-space Green's function theory and calculations of two-photon x-ray absorption (TPA). Our focus is on nonresonant 𝐾-shell TPA in metallic Cu, which has been observed experimentally at intense x-ray free electron laser (XFEL) sources. The theory is based on an independent particle Green's function treatment of the Kramers-Heisenberg equation and an approximation for the sum over nonresonant intermediate states in terms of a static quadrupole transition operator. XFEL effects are modeled by a partially depleted 𝑑 band. This approach is shown to give results for 𝐾-shell TPA in quantitative agreement with XFEL experiment and with a Bethe-Salpeter equation approach. Furthermore, we also briefly discuss many-body corrections and TPA sum rules.

Approximation methods for many-body systems↗
DOE OSTI2026

Towards time-resolved MicroED grid preparation using mix-and-inject gas dynamic virtual nozzles

Recent progress in gas dynamic virtual nozzle (GDVN) technologies in combination with high-brilliance synchrotron and X-ray free-electron lasers (XFELs) has allowed the visualization of protein dynamics in crystallo by mixing macromolecular protein crystals with a substrate using tunable mixing times on the order of milliseconds to seconds prior to serial X-ray diffraction data collection. This has become the method of choice for high-resolution structure determination of intermediate states. However, such experiments require large counts of crystals of proper sizes for high-resolution data collection, and premium beam times for screening efforts. Cryogenic microcrystal electron diffraction (MicroED) represents a complementary technique that may be a more accessible avenue for time-resolved nanocrystallography compared with serial X-ray diffraction experiments. MicroED can produce full diffraction datasets from just a few submicrometre-thick crystals, and the approach is more readily accessible, requiring standard cryogenic transmission electron microscopy (TEM) equipment available at many universities and institutes. Cryogenic MicroED, like other forms of cryo-EM, begins with rapidly freezing biological material on electron microscopy grids. In the case of MicroED, micro- to nano-crystals (<500 nm thick) are deposited onto electron microscopy grids and plunge-frozen for subsequent electron diffraction data collection. Here, we have incorporated GDVN technology developed originally for XFEL experiments into the freezing process as a first step towards time-resolved studies. We describe the limited deposition efficiency of the model MicroED protein proteinase K on TEM grids using GDVNs, preceding sample vitrification and successful MicroED data collection. We discuss both the initial results from such experiments and the methodological challenges in developing this approach into a reliable workflow for millisecond-to-second time-resolved structural studies of macromolecules. Our results promise a strategy to deposit crystals on grids using GDVNs and determine high-resolution structures by MicroED, constituting a first step towards development of time-resolved MicroED experiments.

MicroED↗
DOE OSTI2021

Electronic surface reconstruction of TiO 2 nanocrystals revealed by resonant inelastic x-ray scattering

The identification of lattice multiphases in TiO 2 nanocrystals is studied by high resolution transmission electron microscope and electron diffraction patterns. Based on the spectroscopic analysis using soft x-ray absorption and resonant inelastic soft x-ray scattering, it is believed that the oxygen vacancies at the interface exhibit structural distortion of the TiO$^{8-}_6$ cluster around the defect site as for the multiphase lattice. We elucidate that the extra 3d electrons nearby induce the inelastic scattering features with the excitation energy dependence owing to different energy relaxation processes, a characteristic of the electron-phonon coupling or the nature of the electron-hole pair at the intermediate state. The manifold dd excitations driven by the strong interaction between Ti-3d and O-2p electrons are noticeably rich, coexisting on both Ti and O sites. Finally, this sophisticated experiment can advance the perspective of nanocomposite TiO 2 for various interactions of surface Ti 3+ in applications of future devices.

36 MATERIALS SCIENCE↗
DOE OSTI2016

SU-G-IeP4-12: Performance of In-111 Coincident Gamma-Ray Counting: A Monte Carlo Simulation

Purpose: The decay of In-111 results in a non-isotropic gamma-ray cascade, which is normally imaged using a gamma camera. Creating images with a gamma camera using coincident gamma-rays from In-111 has not been previously studied. Our objective was to explore the feasibility of imaging this cascade as coincidence events and to determine the optimal timing resolution and source activity using Monte Carlo simulations. Methods: GEANT4 was used to simulate the decay of the In-111 nucleus and to model the gamma camera. Each photon emission was assigned a timestamp, and the time delay and angular separation for the second gamma-ray in the cascade was consistent with the known intermediate state half-life of 85ns. The gamma-rays are transported through a model of a Siemens dual head Symbia “S” gamma camera with a 5/8-inch thick crystal and medium energy collimators. A true coincident event was defined as a single 171keV gamma-ray followed by a single 245keV gamma-ray within a specified time window (or vice versa). Several source activities (ranging from 10uCi to 5mCi) with and without incorporation of background counts were then simulated. Each simulation was analyzed using varying time windows to assess random events. The noise equivalent count rate (NECR) was computed based on the number of true and random counts for each combination of activity and time window. No scatter events were assumed since sources were simulated in air. Results: As expected, increasing the timing window increased the total number of observed coincidences albeit at the expense of true coincidences. A timing window range of 200–500ns maximizes the NECR at clinically-used source activities. The background rate did not significantly alter the maximum NECR. Conclusion: This work suggests coincident measurements of In-111 gamma-ray decay can be performed with commercial gamma cameras at clinically-relevant activities. Work is ongoing to assess useful clinical applications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Picosecond amorphization of SiO 2 stishovite under tension

It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested “high-density glass polymorphs” before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids.

36 MATERIALS SCIENCE↗