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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

The ladder and readout cables of intermediate silicon strip detector for sPHENIX

A new silicon-strip-type detector was developed for precise charged-particle tracking in the central rapidity region of heavy ion collisions. A new detector and collaboration at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory is sPHENIX, which is a major upgrade of the PHENIX detector. The intermediate tracker (INTT) is part of the advanced tracking system of the sPHENIX detector complex together with a CMOS monolithic-active-pixel-sensor based silicon-pixel vertex detector, a time-projection chamber, and a micromegas-based detector. The INTT detector is barrel shaped and comprises 56 silicon ladders. Two different types of strip sensors of 78 micron pitch and 320 micron thick are mounted on each half of a silicon ladder. Each strip sensor is segmented into 8 × 2 and 5 × 2 blocks with lengths of 16 and 20 mm. Strips are read out with a silicon strip-readout (FPHX) chip. In order to transmit massive data from the FPHX to the down stream readout electronics card (ROC), a series of long and high speed readout cables were developed. This document focuses on the silicon ladder, the readout cables, and the ROC of the INTT. The radiation hardness is studied for some parts of the INTT devices in the last part of this document, since the INTT employed some materials from the technology frontier of the industry whose radiation hardness is not necessarily well known.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Reaction plane correlated triangular flow in Au + Au collisions at $\sqrt{s_{NN}}$ = 3 GeV

Here, we measure triangular flow relative to the reaction plane at 3 GeV center-of-mass energy in Au + Au collisions at the BNL Relativistic Heavy Ion Collider. A significant v 3 signal for protons is observed, which increases for higher rapidity, higher transverse momentum, and more peripheral collisions. The triangular flow is essentially rapidity-odd with a slope at midrapidity, dv 3 /dy| (y=0) , opposite in sign compared to the slope for directed flow. No significant v 3 signal is observed for charged pions and kaons. Comparisons with models suggest that a mean field potential is required to describe these results, and that the triangular shape of the participant nucleons is the result of stopping and nuclear geometry.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Hadronization of heavy quarks

Heavy-flavor hadrons produced in ultrarelativistic heavy-ion collisions are a sensitive probe for studying hadronization mechanisms of the quark-gluon-plasma. In this paper, we survey how different transport models for the simulation of heavy-quark diffusion through a quark-gluon plasma in heavy-ion collisions implement hadronization and how this affects final state observables. Utilizing the same input charm-quark distribution in all models at the hadronization transition, we find that the transverse-momentum dependence of the nuclear modification factor of various charm hadron species has significant sensitivity to the hadronization scheme. In addition, the charm-hadron elliptic flow exhibits a nontrivial dependence on the elliptic flow of the hadronizing partonic medium.

Atomic, Nuclear and Particle Physics↗
DOE OSTI2024

Quarkonium polarization in medium from open quantum systems and chromomagnetic correlators

Here, by considering the Markovian condition and applying the Wigner transformation upon the diagonal spin components of the quarkonium density matrix with the semiclassical expansion, we systematically derive the Boltzmann transport equation for quarkonia with polarization dependence in the quantum optical limit. Unlike the spin-independent collision terms governed by certain chromoelectric field correlators, new gauge invariant correlators of chromomagnetic fields determine the recombination and dissociation terms with polarization dependence at the order we are working. We also derive a Lindblad equation describing the in-medium transitions between spin-singlet and spin-triplet heavy quark-antiquark pairs in the quantum Brownian motion limit. The Lindblad equation is governed by new transport coefficients defined in terms of the chromomagnetic field correlators. Our formalism is generic and valid for both weakly coupled and strongly coupled quark gluon plasmas. It can be further applied to study spin alignment of vector quarkonia in heavy ion collisions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Heavy ion collisions from $\sqrt{s_{NN}}$ of 62.4 GeV down to 7.7 GeV in the EPOS4 framework

The EPOS4 project is an attempt to construct a realistic model for describing relativistic collisions of different systems, from proton-proton (𝑝⁢𝑝) to nucleus-nucleus (𝐴⁢𝐴), at energies from several TeV per nucleon down to several GeV. We argue that a parallel scattering formalism (as in EPOS4) is relevant for primary scatterings in 𝐴⁢𝐴 collisions above 4 GeV, whereas sequential scattering (cascade) is appropriate below. We present briefly the basic elements of EPOS4, and then investigate heavy ion collisions from 62.4 GeV down to 7.7 GeV, to understand how physics changes with energy, studying in particular the disappearance of the fluid component at low energies.

Monte Carlo methods↗
DOE OSTI2024

Measurements of charged-particle multiplicity dependence of higher-order net-proton cumulants in p + p collisions at $\sqrt{s}$ = 200 GeV from STAR at RHIC

We report on the charged-particle multiplicity dependence of net-proton cumulant ratios up to sixth order from $\sqrt{s}$ = 200 GeV p+p collisions at the Relativistic Heavy Ion Collider (RHIC). The measured ratios C 4 /C 2 , C 5 /C 1 , and C 6 /C 2 decrease with increased charged-particle multiplicity and rapidity acceptance. Neither the Skellam baselines nor PYTHIA8 calculations account for the observed multiplicity dependence. In addition, the ratios C 5 /C 1 and C 6 /C 2 approach negative values in the highest-multiplicity events, which implies that thermalized QCD matter may be formed in p+p collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

New Data-Driven Constraints on the Sign of Gluon Polarization in the Proton

Recently, the possible existence of negative gluon helicity Δ g has been observed to be compatible with existing empirical constraints, including from jet production in polarized proton-proton collisions at the Relativistic Heavy Ion Collider, and lattice QCD data on polarized gluon Ioffe time distributions. We perform a new global analysis of polarized parton distributions in the proton with new constraints from the high- x region of deep-inelastic scattering (DIS). A dramatic reduction in the quality of the fit for the negative Δ g replicas compared to those with positive Δ g suggests that the negative Δ g solution cannot simultaneously account for high- x polarized DIS data along with lattice and polarized jet data. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the transverse energy density in Measurement of the transverse energy density in Au + Au collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV with the sPHENIX detector

Here, this paper reports measurements of the transverse energy per unit pseudorapidity (𝑑⁢𝐸 𝑇 /𝑑⁢𝜂) produced in Au + Au collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV, performed with the sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The results cover the pseudorapidity range |𝜂| < 1.1 and constitute the first such measurement performed using a hadronic calorimeter at RHIC. Measurements of 𝑑⁢𝐸 𝑇 /𝑑⁢𝜂 are presented for a range of centrality intervals and the average 𝑑⁢𝐸 𝑇 /𝑑⁢𝜂 as a function of the number of participating nucleons, 𝑁 part , is compared to a variety of Monte Carlo heavy-ion event generators. The results are in agreement with previous measurements at RHIC, and feature an improved granularity in 𝜂 and improved precision in low-𝑁 part events.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of inclusive jet cross section and substructure in 𝑝 + 𝑝 collisions at $\sqrt{s}$ = 200 GeV

The jet cross section and jet-substructure observables in 𝑝 + 𝑝 collisions at $\sqrt{s}$ =200 GeV were measured by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC). Jets are reconstructed from charged-particle tracks and electromagnetic-calorimeter clusters using the anti-𝑘 𝑡 algorithm with a jet radius of 𝑅 = 0.3 for jets with transverse momentum within 8.0 < 𝑝 𝑇 < 40.0 GeV/𝑐 and pseudorapidity |𝜂| < 0.15. Measurements include the jet cross section, as well as distributions of SoftDrop-groomed momentum fraction (𝑧 𝑔 ), charged-particle transverse momentum with respect to jet axis (𝑗 𝑇 ), and radial distributions of charged particles within jets (𝑟). Also measured was the distribution of 𝜉 = −ln⁡(𝑧), where 𝑧 is the fraction of the jet momentum carried by the charged particle. The measurements are compared to theoretical next-to and next-to-next-to-leading-order calculations, the PYTHIA and H erwig event generators, and to other existing experimental results. Indicated from these measurements is a lower particle multiplicity in jets at RHIC energies when compared to models. Also noted are implications for future jet measurements with sPHENIX at RHIC as well as at the future Electron-Ion Collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Unveiling Baryon Charge Carriers through Charge Stopping in Isobar Collisions

Utilizing a comprehensive (3 + 1)⁢D relativistic hydrodynamic framework with multiple conserved charge currents and charge-dependent lattice-QCD-based equation of state, we study the baryon and electric charge number deposition at midrapidity in isobar Ru + Ru and Zr + Zr collisions at the center of mass energy $\sqrt{s}_{NN}$ = 200 GeV. Comparing our predictions with upcoming experimental data from the Relativistic Heavy Ion Collider will shed light on the existence of baryon junctions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Detecting anomalous C P violation in heavy-ion collisions through baryon-electric charge correlations

The chiral magnetic effect and the chiral vortical effect induce a correlation between baryon and electric currents. Here we show that this correlation can be detected using a new observable: a mixed baryon-electric charge correlator. This correlator is proportional to the baryon asymmetry, suggesting a novel way to separate the chiral effects from the background in heavy-ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Observation of Strong Nuclear Suppression in Exclusive J/ψ Photoproduction in Au + Au Ultraperipheral Collisions at RHIC

We report a measurement of exclusive J/ψ and ψ⁡(2⁢s) photoproduction in Au+Au ultraperipheral collisions at √s NN = 200 GeV using the STAR detector. For the first time, (i) the ψ⁡(2⁢s) photoproduction in midrapidity at the Relativistic Heavy-Ion Collider has been experimentally measured; (ii) nuclear suppression factors are measured for both the coherent and incoherent J/ψ production. At average 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. The stronger suppression observed in the incoherent production provides a new experimental handle to study the initial-state parton density in heavy nuclei. As a result, data are compared with theoretical models quantitatively.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Energy dependence of polarized 𝛾⁢𝛾 → 𝑒 + ⁢ 𝑒− in peripheral Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 and 200 GeV with the STAR experiment at RHIC

We report the differential yields at mid-rapidity of the Breit-Wheeler process (𝛾⁢𝛾 → 𝑒 + ⁢𝑒 − ) in peripheral Au+Aucollisions at $\sqrt{s_{NN}}$ = 54.4 and 200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC), as a function of energy $\sqrt{s_{NN}}$, 𝑒 + ⁢𝑒 − transverse momentum 𝑝 T , 𝑝$^{2}_{T}$, invariant mass 𝑀 𝑒⁢𝑒 , and azimuthal angle. In the invariant mass range of 0.4 < 𝑀 𝑒⁢𝑒 < 2.6GeV/𝑐 2 at low transverse momentum (𝑝 T < 0.15GeV/𝑐), the yields increase while the pair √⟨𝑝$^{2}_{T}$⟩ decreases with increasing $\sqrt{s_{NN}}$, a feature that is correctly predicted by the QED calculation. Here, the energy dependencies of the measured quantities are sensitive to the nuclear form factor, infrared divergence and photon polarization. The data are compiled and used to extract the charge radius of the Au nucleus.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Charm and bottom hadrons in hot hadronic matter

Heavy quarks, and the hadrons containing them, are excellent probes of the QCD medium formed in high-energy heavy-ion collisions, as they provide essential information on the transport properties of the medium and how quarks color-neutralize into hadrons. Large theoretical and phenomenological efforts have been dedicated thus far to assess the diffusion of charm and bottom quarks in the quark–gluon plasma and their subsequent hadronization into heavy-flavor (HF) hadrons. However, the fireball formed in heavy-ion collisions also features an extended hadronic phase, and therefore any quantitative analysis of experimental observables needs to account for the rescattering of charm and bottom hadrons. This is further reinforced by the presence of a QCD cross-over transition and the notion that the interaction strength is maximal in the vicinity of the pseudo-critical temperature. We review existing approaches for evaluating the interactions of open HF hadrons in a hadronic heat bath and the pertinent results for scattering amplitudes, spectral functions and transport coefficients. While most of the work to date has focused on D -mesons, we also discuss excited states as well as HF baryons and the bottom sector. Both the HF hadro-chemistry and bottom observables will play a key role in future experimental measurements. We also conduct a survey of transport calculations in heavy-ion collisions that have included effects of hadronic HF diffusion and assess its impact on various observables.

effective field theories↗
DOE OSTI2024

Probing nuclear structure of heavy ions at energies available at the CERN Large Hadron Collider

We perform high-statistics simulations to study the impacts of nuclear structure on the ratios of anisotropic flow observables in 208 Pb + 208 Pb and 129 Xe + 129 Xe collisions at the Large Hadron Collider. Even with 40% difference in atomic numbers between 208 Pb and 129 Xe nuclei, the ratios of anisotropic flow in the same centrality class between the two collision systems are strongly affected by the nuclear structure inputs in the initial state. The ratios of v 2 ⁡{4}/v 2 ⁡{2} in these collisions are sensitive to the nuclear skin thickness of the colliding nuclei, providing indirect constraints on the nuclei's neutron skin. In conclusion, our model predictions serve as a benchmark to compare with experimental measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Relaxation times for disoriented isospin condensates in high energy heavy ion collisions

Fluctuations between charged and neutral kaons measured by the ALICE Collaboration in Pb-Pb collisions at the CERN Large Hadron Collider (LHC) exceed conventional explanations. Previously it was shown that if the scalar condensate is accompanied by an electrically neutral isospin-1 field then the combination can produce large equilibrium fluctuations where ⟨$\overline{𝑢}$ ⁢𝑢⟩≠⟨ $\overline{𝑑}$𝑑⟩. Hadronizing strange and antistrange quarks might then strongly fluctuate between charged ($\overline{𝑢}$⁢𝑠 or $\overline{𝑠}$⁢𝑢) and neutral (𝑑⁢$\overline{𝑠}$⁢ or 𝑠⁢$\overline{𝑑}$) kaons. Here, we estimate the times for the condensates to achieve their equilibrium probability distributions within causal volumes in high energy heavy ion collisions. This is achieved by modeling the temperature dependence of the condensates, mesonic collective excitations, decay rates of the associated fields, and employing the Langevin and Fokker-Planck equations. Within this model, we find that the equilibration times are short compared with the expansion time, making disoriented isospin condensates a viable explanation for the anomalous fluctuations observed at the LHC.

Quark-gluon plasma↗
DOE OSTI2024

Charmonium Transport in Heavy-Ion Collisions at the LHC

We provide an update on our semi-classical transport approach for quarkonium production in high-energy heavy-ion collisions, focusing on 𝐽/𝜓 and 𝜓(2𝑆) mesons in 5.02 TeV Pb-Pb collisions at the Large Hadron Collider (LHC) at both forward and mid-rapidity. In particular, we employ the most recent charm-production cross sections reported in pp collisions, which are pivotal for the magnitude of the regeneration contribution, and their modifications due to cold-nuclear-matter (CNM) effects. Multi-differential observables are calculated in terms of nuclear modification factors as a function of centrality, transverse momentum, and rapidity, including the contributions from feeddown from bottom hadron decays. For our predictions for 𝜓(2𝑆) production, the mechanism of sequential regeneration relative to the more strongly bound 𝐽/𝜓 meson plays an important role in interpreting recent ALICE data.

Astronomy & Astrophysics↗