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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Nucleon off-shell structure and the free neutron valence structure from A=3 inclusive electron scattering measurements

Understanding the differences between the distribution of quarks bound in protons and neutrons is key for constraining the mechanisms of SU(6) spin-flavor symmetry breaking in Quantum Chromodynamics (QCD). While vast amounts of proton structure measurements were done, data on the structure of the neutron is much more spars as experiments typically extract the structure of neutrons from measurements of light atomic nuclei using model-dependent corrections for nuclear effects. Recently the MARATHON collaboration performed such an extraction by measuring inclusive deep-inelastic electron-scattering on helium-3 and tritium mirror nuclei where nuclear effects are expected to be similar and thus be suppressed in the helium-3 to tritium ratio. Here we evaluate the model dependence of this extraction by examining a wide range of models including the effect of using instant-form and light-cone nuclear wave functions and several different parameterizations of nucleon modification effects, including those with and without isospin dependence. We find that, while the data cannot differentiate among the different models of nuclear structure and nucleon modification, they consistently prefer a neutron-to-proton structure function ratio of at $x_B \rightarrow 1$ of $\sim 0.4$ with a typical uncertainty ($1\sigma$) of $\sim0.05$ and $\sim0.10$ for isospin-independent and isospin-dependent modification models, respectively. While strongly favoring SU(6) symmetry breaking models based on perturbative QCD and the Schwinger-Dyson equation calculation, the MARATHON data do not completely rule out the scalar di-quark models if an isospin-dependent modification exist.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

First demonstration of a triton beam using target normal sheath acceleration

Tritiated titanium targets were irradiated by the short-pulse OMEGA EP laser (1.25 kJ, 10 ps) to generate a laser accelerated pulsed beam of tritons by target normal sheath acceleration. Using a Thomson parabola, the beam was found to contain 10 12 tritons per pulse, with a mean energy of 2.2 MeV and an exponential tail reaching up to 10 MeV. In a separate experiment, the triton beam was directed onto a secondary deuterated polyethylene (CD) target to induce deuterium–tritium (D–T) nuclear reactions. Using neutron time-of-flight spectrometers, approximately 10 8 D–T fusion neutrons were observed per laser pulse. Furthermore, this triton beam presents new research opportunities for the study of the 3 H(t, 2n) 4 He reaction and di-neutron transfers to lithium and beryllium that may produce exotic neutron-rich nuclei of interest to basic nuclear science, astrophysics, and inertial confinement fusion technology.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Unveiling the dynamics of little-bang nucleosynthesis

High-energy nuclear collisions provide a unique site for the synthesis of both nuclei and antinuclei at temperatures of kT ≈ 100 – 150 MeV. In these little bangs of transient collisions, a quark-gluon plasma (QGP) of nearly vanishing viscosity is created, which is believed to have existed in the early universe within the first few microseconds after the Big Bang. Analyses of identified particles produced in these little bangs based on the statistical hadronization model for the QGP have suggested that light (anti)nuclei are produced from the QGP as other hadrons and their abundances are little affected by later hadronic dynamics. Here, we find a strong reduction of the triton yield by about a factor of 1.8 in high-energy heavy-ion collisions based on a kinetic approach that includes the effects of hadronic re-scatterings, particularly that due to pion-catalyzed multi-body reactions. This finding is supported by the latest experimental measurements and thus unveils the important role of hadronic dynamics in the little-bang nucleosynthesis.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Tagging efficiency study of incoherent diffractive vector meson production at the second interaction region at the Electron-Ion Collider

The Electron-Ion Collider (EIC) is an upcoming accelerator facility aimed at exploring the properties of quarks and gluons in nucleons and nuclei, shedding light on their structure and dynamics. The inaugural experimental apparatus, ePIC (electron-Proton and Ion Collider), is designed as a general-purpose detector to address the National Academy of Sciences and the Nuclear Science Advisory Committee physics program at the EIC. The wider EIC community is strongly supporting a second interaction region and an associated second detector to enhance the full science program. In this study, we evaluate how this second interaction region and detector can be complementary to ePIC. The layout of an interaction region for the second detector offers a secondary focus that provides better forward detector acceptance at scattering angles near θ ~ 0 mrad, which can specifically enhance the exclusive, tagging, and diffractive physics program. Here, this article presents an analysis of a tagging program using the second interaction region layout with incoherent diffractive vector meson production. The current design of the second EIC interaction region is evaluated for its vetoing capabilities of incoherent events required for the study of coherent diffractive measurements. We find an increased vetoing performance compared to the ePIC interaction region, thus improving measurements which are important for the spatial imaging of nucleons and nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Toward scalable quantum computations of atomic nuclei

We solve the nuclear two-body and three-body bound states via quantum simulations of pionless effective field theory on a lattice in position space. While the employed lattice remains small, the usage of local Hamiltonians including two- and three-body forces ensures that the number of Pauli terms scales linearly with increasing numbers of lattice sites. We use an adaptive ansatz grown from unitary coupled cluster theory to parametrize the ground states of the deuteron and 3 He, compute their corresponding energies, and analyze the scaling of the required computational resources. Our quantum simulations reproduce exact benchmarks for 2 H and 3 He within 100 keV, requiring at most 30 layers in the ansatz and thus resulting in modest circuit depths. Additionally, we find the number of shots required to reach a given precision scales linearly in the lattice size and more mildly in the system size. Furthermore, based on the agreement with exact benchmarks and mild scaling, we conclude that this can be an efficient, scalable approach for quantum computations of nuclear ground states, particularly to prepare initial states for quantum phase estimation or other filtering algorithms.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Search for an s -wave resonance in Li 7 just above the proton-decay threshold

Near-threshold resonances play an important role in nucleosynthesis and applied nuclear science. The study of nuclei removed from stability has greatly extended the list of resonances close to decay thresholds. The no core shell model with continuum (NCSMC) recently predicted an s-wave resonance just above the proton-decay threshold of 7 Li at an excitation energy of 10.2 MeV. This potential case of a near-threshold resonance is dependent on the quantum mechanics of the p + 6 He fragments extended into the continuum. Further, the 6 He(d,n) 7 Li* reaction was employed in an attempt to populate this resonance and search for its proton decay via the invariant-mass method. No evidence of this resonance was found. However, the data collected in this search led to better constraints on the energy and width of the isobaric analog state (IAS) with (J π ,T) = (3/2 - , 3/2) and revealed a new weak resonance just above the IAS in energy, predicted by the NCSMC as a (J π , T ) = (3/2 – , 1/2) state and potentially a part of the antianalog structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Efficacy of the symmetry-adapted basis for ab initio nucleon-nucleus interactions for light- and intermediate-mass nuclei

We study the efficacy of a new ab initio framework that combines the symmetry-adapted (SA) no-core shell-model approach with the resonating group method (RGM) for unified descriptions of nuclear structure and reactions. We obtain ab initio neutron-nucleus interactions for 4 He, 16 O, and 20 Ne targets, starting with realistic nucleon-nucleon potentials. We discuss the effect of increasing model space sizes and symmetry-based selections on the SA-RGM norm and direct potential kernels, as well as on phase shifts, which are the input to calculations of cross sections. We demonstrate the efficacy of the SA basis and its scalability with particle numbers and model space dimensions, with a view toward ab initio descriptions of nucleon scattering and capture reactions up through the medium-mass region.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC

This work reports femtoscopic correlations of p – – p ($\overline{p}$ – – $\overline{p}$) and p – – d ($\overline{p}$ – – $\overline{d}$) pairs measured in Pb–Pb collisions at center-of-mass energy per nucleon $\sqrt{s_{NN}}$ = 5.02 TeV in the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass (m T ) and on the average charge particle multiplicity $\langle$dN ch /dη$\rangle$ 1/3 for three centrality intervals (0–10%, 10 – – 30 %, 30 – – 50 %). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p–d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p-(p-n) system, due to the large inter-particle distances in Pb–Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at 2.73$^{+0.05}_{–0.05}$ and 3.10$^{+1.04}_{–0.86}$ fm, respectively, for the 30–50% centrality collisions. Moreover, the m T -scaling obtained for the p–p and p–d systems is compatible within 1σ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Ab initio symmetry-adapted approaches to nuclear reactions

In this review, we discuss recent applications of the ab initio symmetry-adapted no-core shell-model (SA-NCSM) theory for study and prediction of structure and reactions of stable and unstable nuclei from light to medium mass range. We explore structure properties of neutron-rich He, Li, and Mg isotopes, with a focus on nuclear collectivity, clustering, and spectroscopic factors, as well as multi-particle excitations of utmost significance in the proximity of the drip lines. In addition, we present extensions of the SA-NCSM with continuum for determining the microscopic structure of reaction fragments, which enables calculations of reaction cross sections for targets from the lightest He to 40Ca, rooted in first principles. We illustrate this for neutron and proton elastic scattering, deuteron and alpha capture reactions, and alpha knock-out reactions. Furthermore, we discuss microscopic optical potentials with uncertainty quantification, a critical ingredient in many reaction models. As a result, we also discuss the impact of alpha clustering on reactions of significance to nuclear astrophysics, as well as on beta decays and beyond-the-standard-model physics.

Ab initio approaches to nuclear reactions↗
DOE OSTI2021

Two- and three-nucleon contact interactions and ground-state energies of light- and medium-mass nuclei

Classes of two-nucleon (2N) contact interactions are developed in configuration space at leading order (LO), next-to-leading order (NLO), and next-to-next-to-next-to-leading order (N3LO) by fitting the experimental singlet np scattering length and deuteron binding energy at LO, and np and pp scattering data in the laboratory-energy ranges 0–15 MeV at NLO and 0–25 MeV at N3LO. These interactions are regularized by including two Gaussian cutoffs, one for T = 0 and the other for T = 1 channels. The cutoffs are taken to vary in the ranges R 0 = (1.5 –2.3) fm and R 1 = (1.5 –3.0) fm. The 780 (1100) data points up to 15 (25) MeV energy, primarily differential cross sections, are fitted by the NLO (N3LO) models with a χ 2 / datum about 1.7 or less (well below 1.5), when harder cutoff values are adopted. As a first application, we report results for the binding energies of nuclei with mass numbers A = 3 –6 and 16 obtained with selected LO and NLO 2N models both by themselves as well as in combination with a LO three-nucleon (3N) contact interaction. The latter is characterized by a single low-energy constant that is fixed to reproduce the experimental 3 H binding energy. The inclusion of the 3N interaction largely removes the sensitivity to cutoff variations in the few-nucleon systems and leads to predictions for the 3 He and 4 He binding energies that cluster around 7.8 and 30 MeV, respectively. However, in 16 O this cutoff sensitivity remains rather strong. Finally, predictions at LO only are also reported for medium-mass nuclei with A = 40 , 48, and 90.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Quantifying resonance behavior in the fusion of O 17 with C 12 at above-barrier energies

Recent measurement of the fusion excitation function for 17 O + 12 C reported the significant suppression of the fusion cross section at E c.m. ≈ 14 MeV. This suppression was hypothesized to signal the existence of a 16 O + n + 12 C molecular configuration. Using the active-target detector MuSIC@Indiana provided an effective means of reexamining the fusion excitation function for 17 O + 12 C.The accuracy of this thick-target measurement is strengthened through comparison with the thin-target measurement of the excitation function for 17 F + 12 C. Furthermore, the result provides important information about the dependence of the average fusion cross section for the oxygen isotopic chain on neutron excess.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

First Measurement of Discrimination between Helium and Electron Recoils in Liquid Xenon for Low-Mass Dark Matter Searches

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading α particles from Po 210 with a gold foil situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurements of Chemical Potentials in Pb-Pb Collisions at $\sqrt{s_{NN}}$=5.02 TeV

This Letter presents the most precise measurement to date of the matter-antimatter imbalance at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 5.02 TeV. Using the Statistical Hadronization framework, it is possible to obtain the value of the electric charge and baryon chemical potentials, μ Q = -0.18 ± 0.90 MeV and μ B = 0.71 ± 0.45 MeV, with unprecedented precision. A centrality-differential study of the antiparticle-to-particle yield ratios of charged pions, protons, Ω baryons, and light (hyper)nuclei is performed. These results indicate that the system created in Pb-Pb collisions at the LHC is on average baryon-free and electrically neutral at midrapidity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Diffractive Physics Program at the Electron–Ion Collider’s (EIC) 2 nd Detector

The Electron–Ion Collider (EIC) will be a novel experimental facility to explore the properties of gluons in nucleons and nuclei, shedding light on their structure and dynamics. The EIC community outlined the physics program of the EIC in a White Paper, and the demanding detector re quirements and potential technologies to deploy at an EIC detector were published in a comprehensive Yellow Report. The general-purpose detector resulting from these efforts, ePIC, is designed to perform a broad physics program. At the same time, the wider EIC community is strongly in favor of a second detector at the EIC. Having two general-purpose collider detec tors to support the EIC science program allows us to have cross-checks and control of systematic uncertainties for potential scientific discoveries. The second detector should feature complementary technologies where possible. It can also focus on specific measurements that are less well-addressed by ePIC. The second interaction region provides potentially improved forward detector acceptance at low pT and a secondary beam focus that enables to enhance the exclusive, tagging, and diffractive physics program. Hereby, I will present the potential capabilities of the second detector and discuss studies related to its diffractive physics program.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Active Galactic Nuclei Continuum Reverberation Mapping Based on Zwicky Transient Facility Light Curves

We perform a systematic survey of active galactic nuclei (AGNs) continuum lags using ~3 days cadence gri-band light curves from the Zwicky Transient Facility. We select a sample of 94 type 1 AGNs at z < 0.8 with significant and consistent inter-band lags based on the interpolated cross-correlation function method and the Bayesian method JAVELIN. Within the framework of the "lamp-post" reprocessing model, our findings are: (1) The continuum emission (CE) sizes inferred from the data are larger than the disk sizes predicted by the standard thin-disk model. (2) For a subset of the sample, the CE size exceeds the theoretical limit of the self-gravity radius (12 lt-days) for geometrically thin disks. (3) The CE size scales with continuum luminosity as R CE ∝ L 0.48±0.04 with a scatter of 0.2 dex, analogous to the well-known radius–luminosity relation of broad Hβ. These findings suggest a significant contribution of diffuse continuum emission from the broad-line region (BLR) to AGN continuum lags. We find that the R CE –L relation can be explained by a photoionization model that assumes ~23% of the total flux comes from the diffuse BLR emission. In addition, the ratio of the CE size and model-predicted disk size anticorrelates with the continuum luminosity, which is indicative of a potential nondisk BLR lag contribution evolving with the luminosity. Finally, a robust positive correlation between the CE size and black hole mass is detected.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Changes of deformed shell gaps at N ~ 100 in light rare-earth, neutron-rich nuclei

There have been compelling evidences indicating that deformed single-particle states in neutron- rich regions are different from those in the stable region. It was pointed out that for the light rare- earth (60Nd, 62Sm, and 64Gd), neutron-rich (N = 98-102) nuclei, the Woods-Saxon potential, the Nilsson modified oscillator potential with "universal" parameters, and the folded Yukawa potential all failed to describe the correct ordering of neutron single-particle states. The location and size of deformed shell gaps in this mass region are under current debate. We propose a modification for the "standard" Nilsson parameters of Bengtsson and Ragnarsson introduced in 1985. The proposed N-dependent spin-orbit interaction brings an effect of the tensor force for the deformed potential, which causes dynamic changes in deformed shell gaps with neutron number and deformation. By applying the modified Nilsson parameters to generate deformed bases for the Projected Shell Model, we demonstrate that the calculation can explain consistently the current experimental data, including the ground state configuration in odd-neutron nuclei, upbending of the yrast moment of inertia at higher spins and the energies of 2-quasineutron 6- and 4- isomers in even-even nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Ground-state properties of light 4 n self-conjugate nuclei in ab initio no-core Monte Carlo shell model calculations with nonlocal N N interactions

We report J π = 0 + ground-state energies and point-proton radii of 4 He, 8 Be, 12 C, 16 O, and 20 Ne nuclei calculated by the ab initio no-core Monte Carlo shell model with the JISP16 and Daejeon16 nonlocal NN interactions. Ground-state energies are obtained in the basis spaces up to seven oscillator shells (N shell =7) with several oscillator energies (ℏω) around the optimal oscillator energy for the convergence of ground-state energies. These energy eigenvalues are extrapolated to obtain estimates of converged ground-state energies in each basis space using energy variances of computed energy eigenvalues. We further extrapolate these energy-variance-extrapolated energies obtained in the finite basis spaces to infinite basis-space results with an empirical exponential form. This form features a dependence on the basis-space size but is independent of the value of ℏω used for the harmonic-oscillator basis functions. Point-proton radii for these states of atomic nuclei are also calculated following techniques employed for the energies. From these results, it is found that the Daejeon16 NN interaction provides good agreement with experimental data up to approximately 16 O, while the JISP16 NN interaction provides good agreement with experimental data up to approximately 12 C. Beyond these nuclei, the interactions produce overbinding accompanied by radii that are too small. These findings suggest and encourage further revisions of nonlocal NN interactions towards the investigation of nuclear structure in heavier-mass regions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Cosmic ray spectrum of protons plus helium nuclei between 6 and 158 TeV from HAWC data

Here, a measurement with high statistics of the differential energy spectrum of light elements in cosmic rays, in particular, of primary H plus He nuclei, is reported. The spectrum is presented in the energy range from 6 to 158 TeV per nucleus. Data was collected with the High Altitude Water Cherenkov (HAWC) Observatory between June 2015 and June 2019. The analysis was based on a Bayesian unfolding procedure, which was applied on a subsample of vertical HAWC data that was enriched to 82% of events induced by light nuclei. To achieve the mass separation, a cut on the lateral age of air shower data was set guided by predictions of CORSIKA/QGSJET-II-04 simulations. The measured spectrum is consistent with a broken power-law spectrum and shows a kneelike feature at around E = 24.0$^{+3.6}_{-3.1}$ TeV , with a spectral index γ = -2.51 ± 0.02 before the break and with γ = -2.83 ± 0.02 above it. The feature has a statistical significance of 4.1σ. Within systematic uncertainties, the significance of the spectral break is 0.8σ.

79 ASTRONOMY AND ASTROPHYSICS↗