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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Heavy quark transport: a theoretical overview

A brief overview on heavy-quark-QGP interactions is presented in this work. Theories at different momentum scales are summarized, including the flavor hierarchy of jet energy loss at high pT, hadronization and the charmed hadron chemistry at medium to low pT, and the extraction of the heavy-quark-QGP potential at low pT. Additionally, recent theoretical developments on heavy quark theories are discussed, such as multi-scale transport models of heavy quarks, probing initial state effects and cold nuclear matter effects using heavy quarks, as well as extending studies from single heavy flavor hadrons to heavy flavor jets.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Measurements of the lightest hypernucleus ($_{Λ}^{3}{H}$): progress and perspective

The hyperon-nucleon (Y-N) interaction is important for the description of the equation-of-state of high baryon density matter. Hypernuclei, the cluster object of nucleons and hyperons, serve as cornerstones of a full understanding of the Y-N interaction. Recent measurements of the lightest known hypernucleus, the hypertriton’s ($_{Λ}^{3}{H}$) and anti-hypertriton’s ($\frac{H}{Λ}$$\bar{H}$) lifetime, mass and Λ separation energy have attracted interests on the subject. Its cross section and collective flow parameters have also been measured in heavy-ion collisions, which have revealed new features on its production mechanism. In this article we summarise recent measurements of $_{Λ}^{3}{H}$, focusing on the heavy-ion collisions. Here, we will discuss their implications for the $_{Λ}^{3}{H}$ properties and the constrains on the Y-N interaction models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Atomically Abrupt Topological p–n Junction

Topological insulators (TI’s) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p–n junctions. Interesting electronic properties of a ‘topological’ p–n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p–n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p–n junction of topological surface states (TSS’s) of a three-dimensional (3D) topological insulator (TI) with an atomically abrupt interface. When a ultrathin Sb film is grown on a 3D TI of Bi 2 Se 3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi 2 Se 3 surface. Thus, the Bi 2 Se 3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS’s as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p–n junctions with the scalability down to atomic dimensions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Hydrogen-induced tunable remanent polarization in a perovskite nickelate

Materials with field-tunable polarization are of broad interest to condensed matter sciences and solid-state device technologies. Here, using hydrogen (H) donor doping, we modify the room temperature metallic phase of a perovskite nickelate NdNiO 3 into an insulating phase with both metastable dipolar polarization and space-charge polarization. We then demonstrate transient negative differential capacitance in thin film capacitors. The space-charge polarization caused by long-range movement and trapping of protons dominates when the electric field exceeds the threshold value. First-principles calculations suggest the polarization originates from the polar structure created by H doping. We find that polarization decays within ~1 second which is an interesting temporal regime for neuromorphic computing hardware design, and we implement the transient characteristics in a neural network to demonstrate unsupervised learning. These discoveries open new avenues for designing ferroelectric materials and electrets using light-ion doping.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Heat control in opto-mechanical system using quantum non-classicality

Cooling of matter to the quantum ground state is a primary directive of quantum control. In other words, to extract entropy from a quantum system, efficient indirect quantum measurements may be implemented. The main objective is the cooling of the oscillator either to its motional ground state or to non-classical states, such as low-number Fock states, squeezed states or entangled states. It is shown that the use of quantum control procedure is better choice for even experimental realizations because it leads to a squeezed steady state with less than one phonon on average. The steady state of system corresponds to cooling of the system.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Applying the Euclidean-signature semi-classical method to the quantum Taub models with a cosmological constant and aligned electromagnetic field

We prove the existence of a countably infinite number of “excited” states for the Lorentzian-signature Taub–Wheeler–DeWitt (WDW) equation when a cosmological constant is present using the Euclidean-signature semi-classical method. We also find a “ground” state solution when both an aligned electromagnetic field and cosmological constant are present; as a result, conjecture that the Euclidean-signature semi classical method can be used to prove the existence of a countably “infinite” number of “excited” states when the two aforementioned matter sources are present. Afterward, we prove the existence of asymptotic solutions to the vacuum Taub–WDW equation using the “no boundary” and “wormhole” solutions of the Taub Euclidean-signature Hamilton–Jacobi equation and compare their mathematical properties. We then discuss the fascinating qualitative properties of the wave functions we have computed. By utilizing the Euclidean-signature semi-classical method in the above manner, we further show its ability to prove the existence of solutions to Lorentzian-signature equations without having to invoke a Wick rotation. This feature of not needing to apply a Wick rotation makes this method potentially very useful for tackling a variety of problems in bosonic relativistic field theory and quantum gravity

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Sterile neutrinos and flavor ratios in IceCube

The flavor composition of astrophysical neutrinos observed in neutrino telescopes is a powerful discriminator between different astrophysical neutrino production mechanisms and can also teach us about the particle physics properties of neutrinos. In this paper, we investigate how the possible existence of light sterile neutrinos can affect these flavor ratios. We consider two scenarios: (i) neutrino production in conventional astrophysical sources, followed by partial oscillation into sterile states; (ii) neutrinos from dark matter decay with a primary flavor composition enhanced in tau neutrinos or sterile neutrinos. Throughout the paper, we constrain the sterile neutrino mixing parameters from a full global fit to short and long baseline data. We present our results in the form of flavor triangles and, for scenario (ii), as exclusion limits on the dark matter mass and lifetime, derived from a fit to IceCube high energy starting events and through-going muons. We argue that identifying a possible flux of neutrinos from dark matter decay may require analyzing the flavor composition as a function of neutrino energy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

DESI DR1 Lyα 1D power spectrum: the optimal estimator measurement

The one-dimensional power spectrum P 1D of Lyα forest offers rich insights into cosmological and astrophysical parameters, including constraints on the sum of neutrino masses, warm dark matter models, and the thermal state of the intergalactic medium. We present the measurement of P 1D using the optimal quadratic maximum likelihood estimator applied to over 300,000 Lyα quasars from Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) survey. This sample represents the largest to date for P 1D measurements and is larger than the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) by a factor of 1.7. We conduct a meticulous investigation of instrumental and analysis systematics and quantify their impact on P 1D . This includes the development of a cross-exposure estimator that eliminates the need to model the pipeline noise and has strong potential for future P 1D measurements. We also present new insights into metal contamination through the 1D correlation function. Using a fitting function we measure the evolution of the Lyα forest bias with high precision: b F (z) = (-0.218 ± 0.002) × ((1 + z)/4) 2.96±0.06 . In a companion validation paper, we substantially extend our previous suite of CCD image simulations to quantify the pipeline's exquisite performance accurately. In another companion paper, we present DR1 P 1D measurements using the Fast Fourier Transform (FFT) approach to power spectrum estimation. These two measurements produce a forest bias parameter that differs by 2.2 sigma. However, our model is simplistic, so this disagreement will be investigated in future work.

Lyman alpha forest↗
DOE OSTI2024

Nuclear structure opportunities with GeV radioactive beams at FAIR

The Facility for Antiproton and Ion Research (FAIR) is in its final construction stage next to the campus of the Gesellschaft für Schwerionenforschung Helmholtzzentrum for heavy-ion research in Darmstadt, Germany. Once it starts its operation, it will be the main nuclear physics research facility in many basic sciences and their applications in Europe for the coming decades. Owing to the ability of the new fragment separator, Super-FRagment Separator, to produce high-intensity radioactive ion beams in the energy range up to about 2 GeV/nucleon, these can be used in various nuclear reactions. This opens a unique opportunity for various nuclear structure studies across a range of fields and scales: from low-energy physics via the investigation of multi-neutron systems and halos to high-density nuclear matter and the equation of state, following heavy-ion collisions, fission and study of short-range correlations in nuclei and hypernuclei. Here, the newly developed reactions with relativistic radioactive beams (R3B) set up at FAIR would be the most suitable and versatile for such studies. An overview of highlighted physics cases foreseen at R3B is given, along with possible future opportunities, at FAIR.

FAIR↗
DOE OSTI2019

Neutron skins as laboratory constraints on properties of neutron stars and on what we can learn from heavy ion fragmentation reactions

The equation of state (EOS) of infinite nuclear matter with a small proton or neutron fraction is a crucial input to determine the properties of neutron stars and compare model predictions to astronomical observations. The so-called symmetry energy is the part of the EOS accounting for the difference in the number of neutrons and protons. Numerous experiments have been devised to assess the symmetry energy and constrain its functional dependence with the nucleon density. Further constraints follow from a stellar modeling using the EOS to reproduce astronomical observations such as neutron star masses and radii. Here, the recent detection of gravitational waves emitted from neutron star mergers and the nucleosynthesis ensuing from these events caused a surge of interest for such studies. Several types of nuclear reactions have been proposed to study the symmetry energy part of the EOS. Some of them consist in determining the neutron skin in nuclei and exploit its correlation with the slope parameter of the symmetry energy. In this article, we explore a particular set of reactions using high-energy (E lab ~ 1 GeV/nucleon) neutron-rich projectiles. We explore measurements of all reaction fragments (a) in the same isotopic chain, i.e., only by removal of neutrons, (b) in all charge-changing channels, and (c) total interaction cross sections. Using Hartree-Fock-Bogoliubov (HBF) predictions for neutron and proton densities with Skyrme interactions, we explore the sensitivity of these cross sections with the neutron skin in nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Direct astrophysical tests of chiral effective field theory at supranuclear densities

Recent observations of neutron stars with gravitational waves and X-ray timing provide unprecedented access to the equation of state (EoS) of cold dense matter at densities difficult to realize in terrestrial experiments. At the same time, predictions for the EoS equipped with reliable uncertainty estimates from chiral effective field theory ( x EFT) allow us to bound our theoretical ignorance. In this work, we analyze astrophysical data using a nonparametric representation of the neutron-star EoS conditioned on x EFT to directly constrain the underlying physical properties of the compact objects without introducing modeling systematics. We discuss how the data alone constrain the EoS at high densities when we condition on x EFT at low densities. Here, we also demonstrate how to exploit astrophysical data to directly test the predictions of x EFT for the EoS up to twice nuclear saturation density, in order to estimate the density at which these predictions might break down. We nd that the existence of massive pulsars, gravitational waves from GW170817, and NICER observations of PSR J0030+0451 favor x EFT predictions for the EoS up to nuclear saturation density over a more agnostic analysis by as much as a factor of 7 for the quantum Monte Carlo (QMC) calculations used in this work. While x EFT predictions using QMC are fully consistent with gravitational-wave data up to twice nuclear saturation density, NICER observations suggest that the EoS stiffens relative to these predictions at or slightly above nuclear saturation density. Additionally, for these QMC calculations, we marginalize over the uncertainty in the density at which x EFT begins to break down, constraining the radius of a 1.4M $\bigodot$ neutron star to R 1.4 = $11.40^{+1.38}_{–1.04}$ ($12.54^{+0.71}_{–0.63}$) km and the pressure at twice nuclear saturation density to p(2n sat ) = $14.2^{+18.1}_{–8.4}$ ($28.7^{+15.3}_{–15.0}$) MeV=fm 3 with massive pulsar and gravitational-wave (and NICER) data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles

In this work, using a (3 + 1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow $v_1 (y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au + Au collisions are considered, performed at $\sqrt {^SNN}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of $v_1$ for both mesons and baryons. We find that the $v_1 (y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Quark-gluon tagging with shower deconstruction: Unearthing dark matter and Higgs couplings

The separation of quark and gluon initiated jets can be an important way to improve the sensitivity in searches for new physics or in measurements of Higgs boson properties. We present a simplified version of the shower deconstruction approach as a novel observable for quark-gluon tagging. Assuming topoclusterlike objects as input, we compare our observable with energy correlation functions and find a favorable performance for a large variety of jet definitions. We address the issue of infrared sensitivity of quark-gluon discrimination. When this approach is applied to dark matter searches in monojet final states, limitations from small signal-to-background ratios can be overcome. We also show that quark-gluon tagging is an alternative way of separating weak boson from gluon-fusion production in the process p+p→H+jet+jet+X.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Confronting gravitational-wave observations with modern nuclear physics constraints

Multi-messenger observations of neutron star (NS) mergers have the potential to revolutionize nuclear astrophysics. They will improve our understanding of nucleosynthesis, provide insights about the equation of state (EOS) of strongly interacting matter at high densities, and enable tests of the theory of gravity and of dark matter. We focus on the EOS, where both gravitational waves (GWs) from neutron-star mergers and X-ray observations from space-based detectors such as NICER will provide more stringent constraints on the structure of neutron stars. Furthermore, recent advances in nuclear theory have enabled reliable calculations of the EOS at low densities using effective field theory based Hamiltonians and advanced techniques to solve the quantum many-body problem. In this paper, we address how the first observation of GWs from GW170817 can be combined with modern calculations of the EOS to extract useful insights about the EOS of matter encountered inside neutron stars. We analyze the impact of various uncertainties, the role of phase transitions in the NS core, and discuss how future observations will improve our understanding of dense matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

A Heavy Ion Fireball freeze-out Dipion Cocktail vs Angular Correlations for Au-Au Collisions at root $\sqrt{S_{NN}}$=200 GeV (Part 2)

The ultra-relativistic heavy ion collision starts out as a state of high density nuclear matter called the Quark Gluon Plasma(QGP) and expands rapidly to freeze-out. During the freeze out phase quarks and gluons form a system of strongly interacting hadrons. These hadrons continue to expand in a thermal manner until no further scattering is possible because the system becomes to dilute.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Laser and Electron Beam Technology for Parity Violating Electron Scattering Measurements

Parity violating electron scattering (PVES) is a precision tool used in a broad program of experiments which include studying the structure of protons and nuclei and searching for new Beyond the Standard Model (BSM) physics. In parity violation electron scattering experiments, a longitudinally polarized electron beam is incident on an unpolarized target. The sign of the longitudinal polarization is changed (making a parity transformation), and the fractional rate difference between right and left helicity states, dσ R and dσ L , is measured. An interference between the electromagnetic and weak amplitudes, M γ and M Z respectively, gives rise to a parity violating asymmetry A PV = $\frac{σ_{R}-σ_{L}}{σ_{R}-σ_{L}}$, defined by the fractional rate difference between right and left helicity states. A PV can be measured to extraordinarily high precision and is proportional to the ratio of the weak and electromagnetic amplitudes. This thesis highlights three such PVES experiments as well as a new polarized beam source which will improve their precision. The PVES experiments are PREX-II, MOLLER, and a 12 C transverse asymmetry measurement at Mainz. Chapters 1-3 of this thesis cover introductions to MOLLER and PREX-II, Chapter 4 contains the results of the 12 C transverse asymmetry measurement at Mainz, and Chapters 5-6 contain the original work performed by this author. PREX-II, the Lead Radius Experiment, measures the weak skin of the 208 Pb nucleus, provides a clean measurement of R N , the RMS radius of neutrons in a heavy nucleus, and constrains the equation of state (EOS) of highly dense matter which is important for describing neutron star structure, heavy ion collisions, and atomic parity violation experiments. The 12 C transverse asymmetry measurement at Mainz, and the future Mainz program of measuring the 208 Pb transverse asymmetry as well, addresses an important systematic correction for PREX and other PVES experiments preformed with heavy-nuclei. MOLLER (Measurement Of Lepton Lepton Electroweak Reaction) is an extremely precise PVES experiment searching for new neutral currents in electron-electron scattering. It’s called MOLLER because it will measure A PV in the Moller ee scattering process, and will infer the weak charge of the electron $Q^e_W$ to extremely high precision. MOLLER is sensitive to new Beyond the Standard Model physics at MeV and multi-TeV scales and will serve as an indirect complementary measurement to direct searches at high energy colliders. To achieve high precision measurements on A PV for MOLLER, we have developed an innovative Rubidium Titanyl Phosphate (RTP) Pockels cell in the polarized source to satisfy both statistical and systematic requirements as regards the electron beam produced. This new ultra-fast RTP cell design uses electric field gradients to provide unprecedented control over helicity correlated beam asymmetries and has been demonstrated to be capable of producing precisely controlled polarized electron beam at Jefferson Laboratory, controlling beam steering down to the nm-level. The precision reached with the RTP cell offers sufficient control over and minimization of helicity correlated beam asymmetries to perform PREX II. The RTP Pockels cell system will provide fast flipping and suitable control helicity correlated beam asymmetries and parity quality beam for the future MOLLER experiment, providing an unprecedented precision on the electron weak charge and electroweak mixing angle.

Palatchi, Caryn↗
DOE OSTI2024

Supplemental Funding - Elementary Particle Physics: Progress and Promise (DE-SC0021427 Final Technical Report)

The field of elementary particle physics explores the universe at the smallest and largest scales to study the fundamental constituents of matter and energy. The United States plays the leading role in this global effort, including some of the world's most extensive scientific collaborations and most complex machines. Current U.S. investments in particle physics are guided by the strategy and priorities identified in the 2014 report of the Particle Physics Project Prioritization Panel (P5), the culmination of a multi-year community-driven process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1974

Neutron stars - General review

A review is presented of those properties of neutron stars upon which there is general agreement and of those areas which currently remain in doubt. Developments in theoretical physics of neutron star interiors are summarized with particular attention devoted to hyperon interactions and the structure of interior layers. Determination of energy states and the composition of matter is described for successive layers, beginning with the surface and proceeding through the central region into the core. Problems encountered in determining the behavior of matter in the ultra-high density regime are discussed, and the effects of the magnetic field of a neutron star are evaluated along with the behavior of atomic structures in the field. The evolution of a neutron star is outlined with discussion centering on carbon detonation, cooling, vibrational damping, rotation, and pulsar glitches. The role of neutron stars in cosmic-ray propagation is considered.

Cameron, A. G. W.↗