Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Nuclear matter”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Nuclear Matter in 1 + 1 Dimensions

We review the solution of QCD in two spacetime dimensions. Following the analysis of Baluni, for a single flavor, the model can be analyzed using Abelian bosonization. The theory can be analyzed in strong coupling, when the quarks are much lighter than the gauge coupling. In this limit, the theory is given by a Luttinger liquid.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Dispersive corrections in elastic electron-nucleus scattering: an investigation in the intermediate energy regime and their impact on the nuclear matter

Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of 12 C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of 12 C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

b b ¯ kinematic correlations in cold nuclear matter

Background: The LHCb Collaboration has studied a number of kinematic correlations between B -hadron pairs through their subsequent decays to J / ψ pairs in p + p collisions at 7 and 8 TeV for four minimum values of the J / ψ p T . Purpose: In this work, these measurements are compared to calculations of b b ¯ pairs and their hadronization and inclusive decays to J / ψ J / ψ are compared to the same observables. Potential cold matter effects on the b b ¯ pair observables are discussed to determine which are most likely to provide insights about the system and why. Methods: The calculations, employing the exclusive HVQMNR code, assume the same intrinsic k T -broadening and fragmentation as in prior work. The pair distributions presented by LHCb are calculated in this approach, both for the parent b b ¯ and the J / ψ J / ψ pairs produced in their decays. The sensitivity of the results to the intrinsic k T broadening is shown. The theoretical uncertainties due to the b quark mass and scale variations on both the initial b b ¯ pairs and the resulting J / ψ pairs are also shown, as is the dependence of the results on the rapidity range of the measurement. Possible effects due to the presence of the nucleus are studied by increasing the size of the k T broadening and modifying the fragmentation function. Results: Good agreement with the LHCb data is found for all observables. The parent b b ¯ distributions are more sensitive to the k T broadening than are the final-state J / ψ pairs. Conclusions: Next-to-leading order calculations with k T broadening, as in prior work, can describe all correlated observables. Multiple measurements of correlated observables are sensitive to different nuclear effects which can help distinguish between them.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Bulk Viscosity in Dense Nuclear Matter

NEUTRON star mergers are an extreme environment where, within milliseconds, the cold, dense matter in neutron stars is dramatically heated to some of the hottest temperatures encountered in astrophysics. Matter in neutron star mergers is located solidly in the interior of the QCD phase diagram, and therefore, the observation and simulation of these mergers provides an opportunity to learn about the strong interaction at a set of densities and temperatures that compliment those obtained in relativistic heavy-ion collisions. Matter during the merger of two neutron stars is far from hydrostatic equilibrium, allowing for the study of not only the equation of state of dense matter, but of transport properties as well. Perhaps the most likely transport property to play a role in neutron star mergers is the bulk viscosity, which acts to resist changes in density. Furthermore, the bulk viscosity of matter at high densities has long been anticipated to damp oscillations in isolated neutron stars, and the study of its role in neutron star mergers is just beginning.

Harris, Steven P.↗
DOE OSTI2022

Nuclear matter effects on jet production at electron-ion colliders

In these proceedings we report recent progress on understanding hadron and jet production in electron-nucleus collisions at the future Electron-Ion Collider [1,2]. These processes will play an essential role in the exploration of the partonic structure of nuclei and the study of parton shower evolution in strongly-interacting matter. We employ the framework of soft-collinear effective theory, generalized to include in-medium interactions, to present the first theoretical results for inclusive hadron and jet cross sections, as well as the jet charge modification in deep inelastic scattering on nuclei. We further demonstrate how to separate initial-state and final-state effects.

Li, Hai Tao↗
NASA NTRS1987

Nuclear techniques in studies of condensed matter

Nuclear techniques have played an important role in the studies of materials over the past several decades. For example, X-ray diffraction, neutron diffraction, neutron activation, and particle- or photon-induced X-ray emission techniques have been used extensively for the elucidation of structural and compositional details of materials. Several new techniques have been developed recently. Four such techniques are briefly reviewed which have great potential in the study and development of new materials. Of these four, Mossbauer spectroscopy, muon spin rotation, and positron annihilation spectroscopy techniques exploit their great sensitivity to the local atomic environments in the test materials. Interest in synchrotron radiation, on the other hand, stems from its special properties, such as high intensity, high degree of polarization, and high monochromaticity. It is hoped that this brief review will stimulate interest in the exploitation of these newer techniques for the development of improved materials.

Singh, Jag J.↗
DOE OSTI2026

Semiclassical treatment of bottomonium suppression and regeneration in 𝑝 + Pb collisions

Here, we study bottomonium suppression in 𝑝 + Pb relative to 𝑝 + 𝑝 collisions at center-of-mass energies of $\sqrt{s_{NN}}$ = 5.02 and 8.16 TeV. Specifically, we combine cold nuclear matter effects (nuclear modifications of the parton densities, energy loss, and momentum broadening) with those from hot nuclear matter (suppression and regeneration) by implementing the formation of a quark-gluon plasma in hydrodynamic simulations. Bottomonium transport in the quark-gluon plasma is evaluated semiclassically, employing two different reaction rates. The first includes quasifree inelastic scattering and gluodissociation employing a perturbative coupling to the medium. The second is based on in-medium 𝑇-matrix calculations where the input potential is constrained by lattice quantum chromodynamics to extract the bottomonium masses and dissociation rates. These semiclassical results are compared to previous calculations in an open quantum system approach and to the experimental data. Predictions for 𝜒 𝑏 suppression at $\sqrt{s_{NN}}$ = 8.16 TeV are also presented.

Physics - Physics of elementary particles and fiel↗