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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Radiative corrections for factorized jet observables in heavy ion collisions

I look at the renormalization of the medium structure function and a medium induced jet function in a factorized cross section for jet substructure observables in Heavy Ion collisions. This is based on the formalism developed in [1], which uses an Open quantum system approach combined with the Effective Field Theory (EFT) for forward scattering to derive a factorization formula for jet observables which work as hard probes of a long lived dilute Quark Gluon Plasma (QGP) medium. I show that the universal medium structure function that captures the observable independent physics of the QGP has both rapidity and UV anomalous dimensions that appear due to medium induced Bremsstrahlung. The resulting Renormalization Group (RG) equations correspond to the BFKL equation and the running of the QCD coupling respectively. I present the first results for the numerical impact of resummation using these RG equations on the mean free path of the jet in the medium. I also briefly discuss the prospects of extending this formalism for a short lived dense medium.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Strong Electromagnetic Fields in Heavy Ion Collisions

Photons play a pivotal role in both theoretical and applied physics, ranging from elementary particle studies to practical technologies. This article explores how ultra-peripheral collisions of heavy ions act as sources of nearly real photons, enabling the investigation of a wide range of photon-induced processes. By applying the equivalent photon approximation, one can study nuclear structure, QED phenomena, and potential new physics, all in a backgroundsuppressed environment.

Bertulani, C. A. [East Texas A & M Univ., Commerce↗
DOE OSTI2023

Energy dependence of light hypernuclei production in heavy-ion collisions from a coalescence and statistical-thermal model perspective

A comparison of light hypernuclei production, from Ultra-relativistic Quantum Molecular Dynamics (UrQMD)+coalescence and the thermal model, in heavy ion collisions over a wide range of beam energies and system sizes is presented. We find that both approaches provide generally similar results, with differences in specific details. Especially the ratios of hypertriton to Λ are affected by both the source radius Δr of the coalescence procedure as well as canonical effects. On the other hand, the double ratio S 3 is almost independent of canonical effects, which is in contrast to coalescence. Thus, both the beam energy dependence and centrality dependence of S 3 can be used to constrain the hypertriton source radius. To do so the currently available data are not yet sufficient. Elliptic flow is shown to be unaffected by the source size of the nuclei and an almost perfect mass scaling of the elliptic flow is observed. Furthermore, our predictions further suggest that the existence of the H-dibaryon(ΛΛ) seems ruled out by ALICE data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Accessing tens-to-hundreds femtoseconds nuclear state lifetimes with low-energy binary heavy-ion reactions

A novel Monte Carlo technique has been developed to determine lifetimes of excited states in the tens-to-hundreds femtoseconds range in products of low-energy heavy-ion binary reactions, with complex velocity distributions. The method is based on a detailed study of Doppler-broadened γ-ray lineshapes. Its relevance is demonstrated in connection with the 18 O(7.0MeV/u)+ 181 Ta experiment, performed at GANIL with the AGATA+VAMOS+PARIS setup, to study neutron-rich O, C, N, ... nuclei. Excited states in 17 O and 19 O, with known lifetimes, are used to validate the method over the ~20-400fs lifetime-sensitivity range. Emphasis is given to the unprecedented position resolution provided by γ-tracking arrays, which turns out to be essential for reaching the required accuracy in Doppler-shift correction. The technique is anticipated to be an important tool for lifetime investigations in exotic neutron-rich nuclei, produced with intense ISOL-type beams.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

The high-density equation of state in heavy-ion collisions: constraints from proton flow

Abstract A set of different equations of state is implemented in the molecular dynamics part of a non-equilibrium transport simulation (UrQMD) of heavy-ion collisions. It is shown how different flow observables are affected by the density dependence of the equation of state. In particular, the effects of a phase transition at high density are explored, including an expected reduction in mean $$m_T$$ m T . We also show that an increase in $$v_2$$ v 2 is characteristic for a strong softening of the equation of state. The phase transitions with a low coexistence density, $$n_{\text {CE}}<4 n_0$$ n CE < 4 n 0 , show a distinct minimum in the slope of the directed flow as a function of the beam energy, which would be a clear experimental signal. By comparing our results with experimental data, we can exclude any strong phase transition at densities below $$4n_0$$ 4 n 0 .

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Heavy ion induced e + e − pair production: Theoretical and preliminary experimental efforts

The production of real e + e − pairs is an important quantum electrodynamics phenomenon, that could have significant implications on low energy heavy ion dynamics. Here, we employ an established Schwingerinspired theory to study this effect in nuclear disintegrations. We extend the current framework with a Monte Carlo approach to include non-perturbative contributions. Simultaneously, we supplement our study with a preliminary experimental procedure, via the use of the Global Spectrometer for Positron and Electron Characterization developed at the Texas Petawatt Laser facility of the University of Texas at Austin. Theory and experiment agree within one order of magnitude, which signals promise for further investigations.

Depastas, T.↗
DOE OSTI2022

Flow-plane decorrelations in heavy-ion collisions with multiple-plane cumulants

The azimuthal correlations between local flow planes at different (pseudo)rapidities (η) may reveal important details of the initial nuclear matter density distributions in heavy-ion collisions. Extensive experimental measurements of a factorization ratio (r 2 ) and its derivative (F 2 ) have shown evidence of the longitudinal flow-plane decorrelation. However, nonflow effects also affect this observable and prevent a quantitative understanding of the phenomenon. In this paper, to distinguish decorrelation and nonflow effects, we propose a new cumulant observable, T 2 , which largely suppresses nonflow. Here, the technique sensitivity to different initial-state scenarios and nonflow effects are tested with a simple Monte Carlo model, and in the end, the method is applied to events simulated by a multiphase transport model (AMPT) for Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. We also emphasize that a distinct decorrelation signal requires not only the right sign of an observable but also its proper dependence on the η window of the reference flow plane to be consistent with the pertinent decorrelation picture.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Longitudinal dependence of B and D meson nuclear modifications in heavy-ion collisions at RHIC and the LHC

It is widely acknowledged that heavy flavor probes are sensitive to the properties of the quark-gluon plasma and are often considered an important tool for the plasma tomography studies. Forward rapidity observables can provide further insight on the dynamics of the medium due to the interplay between the medium size and the differences in the production spectra of heavy quark probes. In this proceedings we present the nuclear modification factor R AA 's for B and D mesons, as well as heavy flavor leptons, in the rapidity range -4.0 < y < 4.0 obtained from relativistic Langevin equation with gluon radiation coupled with a (3+1)-dimensional viscous hydrodynamics medium background. Finally, we present comparison with experimental data at mid-rapidity as well as predictions for different rapidity ranges.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Probing criticality with deep learning in relativistic heavy-ion collisions

Systems with different interactions could develop the same critical behavior due to the underlying symmetry and universality. Using this principle of universality, we can embed critical correlations modeled on the 3D Ising model into the simulated data of heavy-ion collisions, hiding weak signals of a few inter-particle correlations within a large particle cloud. Employing a point cloud network with dynamical edge convolution, we are able to identify events with critical fluctuations through supervised learning, and pick out a large fraction of signal particles used for decision-making in each single event.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Exclusive J / ψ , ψ ( 2 s ) , and e + e - pair production in Au + Au ultraperipheral collisions at the BNL Relativistic Heavy Ion Collider

Measurements of exclusive J/ψ, ψ(2⁢s), and electron-positron (e + ⁢e - ) pair photoproduction in Au+Au ultraperipheral collisions are reported by the STAR experiment at $\sqrt{s_{NN}}$ = 200GeV. Here, we report several first measurements at the BNL Relativistic Heavy Ion Collider, which are (i) J/ψ photoproduction with large momentum transfer up to 2.2⁢(GeV/c) 2 , (ii) coherent J/ψ photoproduction associated with neutron emissions from nuclear breakup, (iii) the rapidity dependence of incoherent J/ψ photoproduction, (iv) the ψ⁡(2⁢s) photoproduction cross section at midrapidity, and (v) e + ⁢e - pair photoproduction up to high invariant mass of 6GeV/c 2 . For measurement (ii), the coherent J/ψ total cross section of γ + Au → J/ψ + Au as a function of the center-of-mass energy W γN has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, quantum electrodynamics, and the next-to-leading-order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent J/ψ cross sections of Au nuclei are found to be 71% ± 10% and 36% ± 7%, respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Hydrodynamic description of D meson production in high-energy heavy-ion collisions *

The large values and constituent-quark-number scaling of the elliptic flow of low-p T D mesons imply that charm quarks, initially produced through hard processes, might be partially thermalized through strong interactions with quark-gluon plasma (QGP) in high-energy heavy-ion collisions. To quantify the degree of thermalization of low-p T charm quarks, we compare the D 0 meson spectra and elliptic flow from a hydrodynamic model to experimental data as well as transport model simulations. We use an effective charm chemical potential at the freeze-out temperature to account for the initial charm quark production from hard processes and assume that they are thermalized in the local comoving frame of the medium before freeze-out. D 0 mesons are sampled statistically from the freeze-out hyper-surface of the expanding QGP as described by the event-by-event (3+1)D viscous hydrodynamic model CLVisc. Both the hydrodynamic and transport models can describe the elliptic flow of D 0 mesons at P T < 3 GeV/c as measured in Au+Au collisions at $sqrts_{NN} = 200$ GeV. Though the experimental data on spectra are consistent with the hydrodynamic result at small p T ~ 1 GeV/c, they deviate from the hydrodynamic model at high transverse momentum, GeV/c. The diffusion and parton energy loss mechanisms in the transport model can describe the measured spectra reasonably well within the theoretical uncertainty. Finally, our comparative study indicates that charm quarks only approach local thermal equilibrium at small p T , even though they acquire sizable elliptic flow comparable to light-quark hadrons at both small and intermediate p T .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Heavy ion beam physics at Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams (FRIB) will be the world's premier rare-isotope beam facility. Experiments with the majority (~80%) of the isotope predicted to exist will become available. The FRIB facility is based on a superconducting (SC) heavy ion linac with output energy above 200 MeV/u for any ions at beam power of 400 kW. FRIB includes a target facility for in-flight production of rare isotopes. A three-stage fragment separator will be used to prepare fast rare isotope beams with high-purity for nuclear physics experiments. The installation work of the accelerator and experimental systems is approaching completion and multi-stage beam commissioning activities started in summer 2017 with expected project completion in early 2022. In conclusion, the commencement of operation for users' experiments is planned immediately following the project completion.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Disoriented isospin condensates in heavy-ion collisions

Anomalous neutral to charged kaon correlations measured by the ALICE collaboration have defied usual explanations. We propose that the large fluctuations could arise because of a disoriented isospin condensate where there is an imbalance between up and down condensates at the time kaons hadronize. This could happen in heavy-ion collisions when the quark condensate re-forms as the system cools and the approximate chiral symmetry of QCD is broken. Within the linear sigma model, we show that the energy cost of forming a disoriented isospin condensate is small making it very plausible.

Kapusta, Joseph [University of Minnesota, Minneapo↗
DOE OSTI2022

Structural and thermodynamic evolution of an amorphous SiOC ceramic after swift heavy ion irradiation

Radiation induced structural and energetic changes have been widely studied in crystalline materials, but studied to a much lesser extent in amorphous solids. Using a combination of neutron pair distribution function (PDF) analysis and high temperature oxide melt solution calorimetry, we obtained critical insights into the structural and energetic evolution in a swift heavy ion irradiated amorphous SiOC polymer-derived ceramic. The radiation modified SiOC structure becomes energetically less stable by 24.0±1.6 kJ/mol compared to the unirradiated structure. This destabilization is related to decreased connectivity of the Si-O-C network and destruction of free carbon. In comparison with unirradiated SiOC, the irradiated structure is more likely to become phase separated during subsequent thermal annealing. Here, our study has important implications for evaluating amorphous SiOC ceramic as a possible radiation resistant structure for nuclear applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Fabrication, thermal analysis, and heavy ion irradiation resistance of epoxy matrix nanocomposites loaded with silane-functionalized ceria nanoparticles

This paper describes a detailed understanding of how nanofillers function as radiation barriers within the polymer matrix, and how their effectiveness is impacted by factors such as composition, size, loading, surface chemistry, and dispersion. Here, we designed a comprehensive investigation of heavy ion irradiation resistance in epoxy matrix composites loaded with surface-modified ceria nanofillers, utilizing tandem computational and experimental methods to elucidate radiolytic damage processes and relate them to chemical and structural changes observed through thermal analysis, vibrational spectroscopy, and electron microscopy. A detailed mechanistic examination supported by FTIR spectroscopy data identified the bisphenol A moiety as a primary target for degradation reactions. Results of computational modeling by the Stopping Range of Ions in Matter (SRIM) Monte Carlo simulation were in good agreement with damage analysis from surface and cross-sectional SEM imaging. All metrics indicated that ceria nanofillers reduce the damage area in polymer nanocomposites, and that nanofiller loading and homogeneity of dispersion are key to effective damage prevention. The results of this study represent a significant pathway for engineered irradiation tolerance in a diverse array of polymer nanocomposite materials. Numerous areas of materials science can benefit from utilizing this facile and effective method to extend the reliability of polymer materials.

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

A theoretical study on quasifission and fusion–fission processes in heavy-ion collisions

Despite recent advances and focus on rigorous uncertainty quantification for microscopic models of quantum many-body systems, the uncertainty on the dynamics of those systems has been underexplored. To address this, we have used time-dependent Hartree-Fock to examine the model uncertainty for a collection of low-energy, heavy-ion fusion reactions. Fusion reactions at near-barrier energies represent a rich test-bed for the dynamics of quantum many-body systems owing to the complex interplay of collective excitation, transfer, and static effects that determine the fusion probability of a given system. The model uncertainty is sizable for many of the systems studied and the primary contribution arises from static properties that are ill-constrained, such as the neutron radius of neutron-rich nuclei. These large uncertainties motivate the use of information from reactions to better constrain existing models and to infer static properties from reaction data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Investigation of Nano-Scale Segregation in Nanostructured Ferritic Alloy 14YWT after Heavy Ion Irradiation

Oxide-dispersion-strengthened (ODS) steels, which contain nano-scale Y-Ti-O particles, are being considered for high-temperature radiation environments of nuclear reactors. It is important to accurately characterize the structure of grain boundaries and understand the behavior of segregation at grain boundaries in ODS steels during irradiation. The effect of heavy ion irradiation at 700 °C on Nanostructured Ferritic Alloy 14YWT was investigated using Atom Probe Tomography. Enrichment of Cr occurs at the grain boundaries as well as at nano oxide particle surfaces in the unirradiated sample. The enrichment of Ti and Y at a grain boundary corresponds with Y-Ti-O nano oxide particles with larger size compared to those in the grain, and the Cr enrichment is particularly accentuated at these larger nano oxide particles. The segregation of W occurs at the grain boundaries that are without nano oxide particles. O is segregated at grain boundaries without oxide particles after irradiation. The segregation behavior of Cr, W, Ti, and Y at the grain boundary in the irradiated samples is similar to that in the unirradiated sample. The nano oxide particles embedded in the grain boundary are a primary reason for the increase in Cr segregation at the grain boundary.

36 MATERIALS SCIENCE↗