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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Measurement of the dineutrino system kinematic variables in dileptonic top quark pair production in proton-proton collisions at $\sqrt{s}=13$ TeV

Differential top quark pair production cross sections are measured in the dilepton final states e + e − , μ + μ − , and e ± μ ∓ , as a function of kinematic variables of the two-neutrino system: the transverse momentum $p^{vv}_{\textrm{T}}$ of the dineutrino system, the minimum distance in azimuthal angle between $\vec{p}^{vv}_{\textrm{T}}$ and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at $\sqrt{s}=13$ TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb −1 . The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations.

Hadron-Hadron Scattering↗
DOE OSTI2020

Phase separation and state oscillation of active inertial particles

Active matter systems are of great interest for their novel out-of-equilibrium collective behavior. Active Brownian particles (ABPs) are known to exhibit clustering and motility-induced phase separation, and there have been many studies revealing this rich behavior in the overdamped limit of Brownian motion, where inertial effects are insignificant. In this work, we simulate an Active Inertial Particle (AIP) model where we focus on the underdamped, rather than overdamped limit, to study the interplay between particle inertia and collective behavior, such as phase separation. We show that inertia reduces particle motility due to collisions and a longer time delay for particles to regain speed, thereby suppressing phase separation relative to that observed in the overdamped limit. Additionally, we observe interesting oscillatory behavior between a phase separated steady-state and a homogeneous fluid state that results from inertia-induced collective motion within active clusters due to momentum transfer. Such oscillatory behavior has been reported for ABP systems with particle shape anisotropy, where collective motion is mediated by particle shape anisotropy. Furthermore, we confirm that there is no single characteristic frequency for the oscillatory behavior. The power spectral density is a power law in the high frequency domain, with an exponent close to -2.5.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Classical non-Markovian Boltzmann equation

The modeling of particle transport involves anomalous diffusion, (x²(t) ) ∝ t{sup α} with α ≠ 1, with subdiffusive transport corresponding to 0 < α < 1 and superdiffusive transport to α > 1. These anomalies give rise to fractional advection-dispersion equations with memory in space and time. The usual Boltzmann equation, with only isolated binary collisions, is Markovian and, in particular, the contributions of the three-particle distribution function are neglected. We show that the inclusion of higher-order distribution functions give rise to an exact, non-Markovian Boltzmann equation with resulting transport equations for mass, momentum, and kinetic energy with memory in both time and space. The two- and the three-particle distribution functions are considered under the assumption that the two- and the three-particle correlation functions are translationally invariant that allows us to obtain advection-dispersion equations for modeling transport in terms of spatial and temporal fractional derivatives.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Developing grain boundary diagrams as a materials science tool: A case study of nickel-doped molybdenum

Impurity-based, premelting-like, grain boundary (GB) ''phases'' (complexions) can form in alloys and influence sintering, creep, and microstructural development. Calculation of Phase Diagrams (CalPhaD) methods and Miedema-type statistical interfacial thermodynamic models are combined to forecast the formation and stability of subsolidus quasiliquid GB phases in binary alloys. This work supports a long-range scientific goal of developing ''GB (phase) diagrams'' as a new materials science tool to help controlling the materials fabrication processing and resultant materials properties. Using nickel-doped molybdenum as a model system, a type of GB diagram (called ''{lambda} diagram'') is computed to represent the temperature- and composition-dependent thermodynamic tendency for general GBs to disorder. Subsequently, controlled sintering experiments are conducted to estimate the GB diffusivity as a function of temperature and overall composition, and the experimental results correlate well with the computed GB diagram. Although they are not yet rigorous GB-phase diagrams with well-defined transition lines, the predictability and usefulness of such {lambda} diagrams are demonstrated. Related interfacial thermodynamic models and computational approaches are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Analysis of the 18 F g,m (d,p) 19 F reactions in the rotational model

Spectroscopic strengths for the 18 F g , m ( d , p ) F 19 reactions to members of the ground-state band in F 19 are interpreted in the rotational model. The analysis considers two different coupling schemes, namely, the strong and decoupled limits of the particle rotor model to describe the ground and isomeric states of F 18 , as well as the transitions to the ground-state band in F 19 . Our results, obtained using Nilsson amplitudes for the neutron levels 1 2 [ 220 ] , 3 2 [ 211 ] , and 5 2 [ 202 ] calculated at a deformation ε 2 = 0.32 are in agreement with the measurements and USDB shell-model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei

The recently developed particle-hole dispersive optical model is applied to describe properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. In particular, the double transition density averaged over the energy of the isoscalar monopole excitations is considered for {sup 208}Pb in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Study of performance of the ATLAS transition radiation tracker in run 1 of the LHC: Tracking characteristics

The ATLAS Transition Radiation Tracker (TRT) contains more than 350000 large straw tubes and it is the outermost of the three subsystems of the ATLAS Inner Detector (ID). The TRT contributes substantially to the ATLAS ID resolution for the tracks of high-energy particles, providing excellent particle identification capabilities and electron-pion separation. Basic performance parameters of the TRT related to its tracking function are described in this paper. The data used in this study were collected during the first period of the Large Hadron Collider (LHC) operation in 2012 with a proton collision energy of 8 TeV. The tracking performance of the TRT has been studied in the case of operating with a Xe-based gas mixture and as a function of the straw occupancy. Special attention was paid to investigation of tracking parameters inside hadronic jets. The experimental data and simulation are in reasonable agreement, even within the dense cores of the most energetic jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Bayesian optimization of the Community Land Model simulated biosphere-atmosphere exchange using CO 2 observations from a dense tower network and aircraft campaigns over Oregon

Here, the vast forests and natural areas of the Pacific Northwest comprise one of the most productive ecosystems in the northern hemisphere. The heterogeneous landscape of Oregon poses a particular challenge to ecosystem models. We present a framework using a scaling factor Bayesian inversion to improve the modeled atmosphere-biosphere exchange of carbon dioxide. Observations from 5 CO/CO 2 towers, eddy covariance towers, and airborne campaigns were used to constrain the Community Land Model CLM4.5 simulated terrestrial CO 2 exchange at a high spatial and temporal resolution (1/24°, 3-hourly). To balance aggregation errors and the degrees of freedom in the inverse modeling system, we applied an unsupervised clustering approach for the spatial structuring of our model domain. Data from flight campaigns were used to quantify the uncertainty introduced by the Lagrangian particle dispersion model that was applied for the inversions. The average annual statewide net ecosystem productivity (NEP) was increased by 32% to 29.7 TgC per year by assimilating the tropospheric mixing ratio data. The associated uncertainty was decreased by 28.4% to 29%, on average over the entire Oregon model domain with the lowest uncertainties of 11% in western Oregon. The largest differences between posterior and prior CO 2 fluxes were found for the Coast Range ecoregion of Oregon that also exhibits the highest availability of atmospheric observations and associated footprints. In this area, covered by highly productive Douglas-fir forest, the differences between the prior and posterior estimate of NEP averaged 3.84 TgC per year during the study period from 2012 through 2014.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

The International Linear Collider (Report to Snowmass 2021)

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Double-power-law Feature of Energetic Particles Accelerated at Coronal Shocks

Recent observations have shown that in many large solar energetic particle (SEP) events the event-integrated differential spectra resemble double power laws. We perform numerical modeling of particle acceleration at coronal shocks propagating through a streamer-like magnetic field by solving the Parker transport equation, including protons and heavier ions. We find that for all ion species the energy spectra integrated over the simulation domain can be described by a double power law, and the break energy depends on the ion charge-to-mass ratio as E B ~ (Q/A) α , with α varying from 0.16 to 1.2 by considering different turbulence spectral indices. We suggest that the double-power-law distribution may emerge as a result of the superposition of energetic particles from different source regions where the acceleration rates differ significantly due to particle diffusion. The diffusion and mixing of energetic particles could also provide an explanation for the increase of Fe/O at high energies as observed in some SEP events. Although further mixing processes may occur, our simulations indicate that either a power-law break or rollover can occur near the Sun and predict that the spectral forms vary significantly along the shock front, which may be examined by upcoming near-Sun SEP measurements from the Parker Solar Probe and Solar Orbiter.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Study of neutrino oscillations and flux systematics in the NOvA experiment at Fermilab

The Standard Model of particle physics explains many experimental results using three generations of quarks, leptons, and their interactions, but fails to account for phenomena such as neutrino masses, matter-antimatter asymmetry, gravity, and the hierarchy problem. The study of neutrinos, especially neutrino oscillations, is crucial for advancing Beyond the Standard Model physics and the future of particle physics.newline

Sharma, Prachi [Panjab U.] (ORCID:0000000276586664↗
DOE OSTI2017

Comprehensive model for predicting elemental composition of coal pyrolysis products

Large-scale coal combustion simulations depend highly on the accuracy and utility of the physical submodels used to describe the various physical behaviors of the system. Coal combustion simulations depend on the particle physics to predict product compositions, temperatures, energy outputs, and other useful information. The focus of this paper is to improve the accuracy of devolatilization submodels, to be used in conjunction with other particle physics models. Many large simulations today rely on inaccurate assumptions about particle compositions, including that the volatiles that are released during pyrolysis are of the same elemental composition as the char particle. Another common assumption is that the char particle can be approximated by pure carbon. These assumptions will lead to inaccuracies in the overall simulation. There are many factors that influence pyrolysis product composition, including parent coal composition, pyrolysis conditions (including particle temperature history and heating rate), and others. All of these factors are incorporated into the correlations to predict the elemental composition of the major pyrolysis products, including coal tar, char, and light gases.

01 COAL, LIGNITE, AND PEAT↗
NASA NTRS1995

Bounce-averaged Hamiltonian for charged particles in an axisymmetric but nondipolar model magnetosphere

In order to facilitate bounce-averaged guiding center simulations of geomagnetically trapped particles, we express the kinetic energy of a particle with magnetic coordinates (L,phi) as an analytic function of the first two adiabatic invariants (M,J) and the L value of the field line. The magnetic field model is axisymmetric, consisting of a dipolar vector-B field plus a uniform southward magnetic field parallel to the dipole moment mu(sub E). This model magnetosphere is surrounded by a circular equatorial neutral line whose radius b is an adjustable parameter. Our formulation provides a computationally efficient method for tracing the bounce-averaged adiabatic motion (conserving all three invariants) and nonadiabatic transport (violating the third invariant while conserving the first two invariants) of geomagnetically trapped particles in the model magnetosphere.

Schulz, Michael↗
DOE OSTI2016

Search for a massive invisible particle X 0 in B + → e + X 0 and B + → μ + X 0 decays

We present a search for a non-Standard-Model invisible particle X 0 in the mass range 0.1-1.8GeV/c 2 in B + →e + X 0 and B + →μ+X 0 decays. The results are obtained from a 711 fb -1 data sample that corresponds to 772×10 6 BB pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB e + e - collider. One B meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner B meson. We find no evidence of a signal and set upper limits on the order of 10 -6 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

AN ANALYTICAL MODEL FOR THE CORONAL COMPONENT OF MAJOR SOLAR ENERGETIC PARTICLE EVENTS

We formulate an analytical model of the coronal-phase acceleration observed in the beginning of major solar energetic particle (SEP) events, before the main-phase acceleration associated with coronal mass ejections (CMEs) in solar wind. The model is driven and constrained by the broadband observations of SEPs and CMEs, in particular SEP data from the particle telescope of the Energetic and Relativistic Nuclei and Electron (ERNE) experiment on the Solar and Heliospheric Observatory (SOHO) spacecraft, solar radio spectrograms, and low-corona observations of CMEs. The model is also verified against observations of solar high-energy neutrons and neutron-decay protons. The model suggests SEP acceleration above {approx} 50 MeV nucleon{sup -1} by coronal shock and the shock-amplified turbulence in closed magnetic structures, and particle release at magnetic reconnection between the closed structure of expanding CME and pre-existing open magnetic flux tubes. The analytical model connects parameters of coronal shocks and structures and the SEP parameters in space, which facilitates analysis of multiwavelength data and will assist in further development of coronal acceleration models.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2010

Development and Demonstration of a Computational Tool for the Analysis of Particle Vitiation Effects in Hypersonic Propulsion Test Facilities

In order to improve the understanding of particle vitiation effects in hypersonic propulsion test facilities, a quasi-one dimensional numerical tool was developed to efficiently model reacting particle-gas flows over a wide range of conditions. Features of this code include gas-phase finite-rate kinetics, a global porous-particle combustion model, mass, momentum and energy interactions between phases, and subsonic and supersonic particle drag and heat transfer models. The basic capabilities of this tool were validated against available data or other validated codes. To demonstrate the capabilities of the code a series of computations were performed for a model hypersonic propulsion test facility and scramjet. Parameters studied were simulated flight Mach number, particle size, particle mass fraction and particle material.

Perkins, Hugh Douglas↗
DOE OSTI2013

Dynamic and impact contact mechanics of geologic materials: Grain-scale experiments and modeling

High fidelity treatments of the generation and propagation of seismic waves in naturally occurring granular materials is becoming more practical given recent advancements in our ability to model complex particle shapes and their mechanical interaction. Of particular interest are the grain-scale processes that are activated by impact events and the characteristics of force transmission through grain contacts. To address this issue, we have developed a physics based approach that involves laboratory experiments to quantify the dynamic contact and impact behavior of granular materials and incorporation of the observed behavior indiscrete element models. The dynamic experiments do not involve particle damage and emphasis is placed on measured values of contact stiffness and frictional loss. The normal stiffness observed in dynamic contact experiments at low frequencies (e.g., 10 Hz) are shown to be in good agreement with quasistatic experiments on quartz sand. The results of impact experiments - which involve moderate to extensive levels of particle damage - are presented for several types of naturally occurring granular materials (several quartz sands, magnesite and calcium carbonate ooids). Implementation of the experimental findings in discrete element models is discussed and the results of impact simulations involving up to 5 Multiplication-Sign 105 grains are presented.

58 GEOSCIENCES↗
DOE OSTI2015

Development and validation of a critical gradient energetic particle driven Alfven eigenmode transport model for DIII-D tilted neutral beam experiments

Recent experiments with the DIII-D tilted neutral beam injection (NBI) varying the beam energetic particle (EP) source profiles have provided strong evidence that unstable Alfven eigenmodes (AE) drive stiff EP transport at a critical EP density gradient. Here the critical gradient is identified by the local AE growth rate being equal to the local ITG/TEM growth rate at the same low toroidal mode number. The growth rates are taken from the gyrokinetic code GYRO. Simulation show that the slowing down beam-like EP distribution has a slightly lower critical gradient than the Maxwellian. The ALPHA EP density transport code, used to validate the model, combines the low-n stiff EP critical density gradient AE mid-core transport with the energy independent high-n ITG/TEM density transport model controling the central core EP density profile. For the on-axis NBI heated DIII-D shot 146102, while the net loss to the edge is small, about half the birth fast ions are transported from the central core r/a < 0.5 and the central density is about half the slowing down density. Lastly, these results are in good agreement with experimental fast ion pressure profiles inferred from MSE constrained EFIT equilibria.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗