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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

CMS Physics Results in the LHC Runs 2,3

The Large hadron Collider at CERN and four scientific collaborations: Alice, ATLAS, CMS, LHCb are in operation since September 2008. The accelerator delivered and the experiments processed trillions of events of proton-proton and heavy ions collisions and provided useful data for thousands of physics analyses and publications. The jewel of the published data is a discovery in 2012 of the long anticipated Higgs boson. During the operation time the regular acquisition of data was interleaved with two periods of maintenance, Long-shutdown-1 (2013-2015) and Long-shutdown-2 (2018-2022), which resulted in several improvements to the machine and the experiments. The CMS collaboration recorded to date two large physics datasets of pp collision data. The first dataset, called Run 2, was recorded between 2015 and 2018 with 140fb-1 of integrated luminosity taken at 13TeV of center of mass energy. The second dataset, called Run 3, has just started in 2022 and it has been recording pp collision data at 13.6 TeV of center of mass energy, with 80 fb-1 of data collected till the end of July 2023.For my presentation I selected the most recent results produced by CMS from Run2 and Run 3 which are covering the topics of Higgs boson properties, searches for new particles and additional scalars, top quark production and properties, and I am discussing other interesting models e.g. using SM particles as portals to the Dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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

Observation of Λ Hyperon Local Polarization in 𝑝-Pb Collisions at $\sqrt{s_{NN}}$ = 8.16 TeV

The polarization of the Λ and $\bar{Λ}$ hyperons along the beam direction has been measured in proton-lead (𝑝-Pb) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of 186.0 ± 6.5 nb −1 . A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient 𝑃 𝑧,s⁢2 , is observed. The 𝑃 𝑧,s⁢2 values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed 𝑃 𝑧,s⁢2 values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the 𝑝-Pb results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Λ spin polarization in event-by-event relativistic heavy-ion collisions

We present a systematic study of $\Lambda$ hyperon's polarization observables using event-by-event (3+1)D relativistic hydrodynamics. The effects of initial hot spot size and QGP's specific shear viscosity on the polarization observables are quantified. We examine the effects of the two formulations of the thermal shear tensor on the polarization observables using the same hydrodynamic background. With event-by-event simulations, we make predictions for the Fourier coefficients of $\Lambda$'s longitudinal polarization $P^z$ with respect to the event planes of different orders of anisotropic flow. We propose new correlations among the Fourier coefficients of $P^z$ and charged hadron anisotropic flow coefficients to further test the mapping from fluid velocity gradients to hyperon's polarization. Finally, we present a system size scan with Au+Au, Ru+Ru, and O+O collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV to study the system size dependence of polarization observables at the Relativistic Heavy-ion Collider.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1993

Potential health effects of space radiation

Crewmembers on missions to the Moon or Mars will be exposed to radiation belts, galactic cosmic rays, and possibly solar particle events. The potential health hazards due to these space radiations must be considered carefully to ensure the success of space exploration. Because there is no human radioepidemiological data for acute and late effects of high-LET (Linear-Energy-Transfer) radiation, the biological risks of energetic charged particles have to be estimated from experimental results on animals and cultured cells. Experimental data obtained to date indicate that charged particle radiation can be much more effective than photons in causing chromosome aberrations, cell killing, mutation, and tumor induction. The relative biological effectiveness (RBE) varies with biological endpoints and depends on the LET of heavy ions. Most lesions induced by low-LET radiation can be repaired in mammalian cells. Energetic heavy ions, however, can produce large complex DNA damages, which may lead to large deletions and are irreparable. For high-LET radiation, therefore, there are less or no dose rate effects. Physical shielding may not be effective in minimizing the biological effects on energetic heavy ions, since fragments of the primary particles can be effective in causing biological effects. At present the uncertainty of biological effects of heavy particles is still very large. With further understanding of the biological effects of space radiation, the career doses can be kept at acceptable levels so that the space radiation environment need not be a barrier to the exploitation of the promise of space.

Yang, Chui-Hsu↗
NASA NTRS2001

Shielded Heavy-Ion Environment Linear Detector (SHIELD): an experiment for the Radiation and Technology Demonstration (RTD) Mission

Radiological assessment of the many cosmic ion species of widely distributed energies requires the use of theoretical transport models to accurately describe diverse physical processes related to nuclear reactions in spacecraft structures, planetary atmospheres and surfaces, and tissues. Heavy-ion transport models that were designed to characterize shielded radiation fields have been validated through comparison with data from thick-target irradiation experiments at particle accelerators. With the RTD Mission comes a unique opportunity to validate existing radiation transport models and guide the development of tools for shield design. For the first time, transport properties will be measured in free-space to characterize the shielding effectiveness of materials that are likely to be aboard interplanetary space missions. Target materials composed of aluminum, advanced composite spacecraft structure and other shielding materials, helium (a propellant) and tissue equivalent matrices will be evaluated. Large solid state detectors will provide kinetic energy and charge identification for incident heavy-ions and for secondary ions created in the target material. Transport calculations using the HZETRN model suggest that 8 g cm -2 thick targets would be adequate to evaluate the shielding effectiveness during solar minimum activity conditions for a period of 30 days or more.

NASA Center LaRC↗
DOE OSTI2020

Far-from-equilibrium search for the QCD critical point

Initial conditions for relativistic heavy-ion collisions may be far from equilibrium (i.e., there are large initial contributions from the shear stress tensor and bulk pressure) but it is expected that on very short time scales the dynamics converge to a universal attractor that defines hydrodynamic behavior. Thus far, studies of this nature have only considered an idealized situation at LHC energies (high temperatures T and vanishing baryon chemical potential µ B = 0) but, in this work, we investigate for the first time how far-from-equilibrium effects may influence experimentally driven searches for the Quantum Chromodynamic critical point at RHIC. We find that the path to the critical point is heavily influenced by far from equilibrium initial conditions where viscous effects lead to dramatically different {T, µ B } trajectories through the QCD phase diagram. We compare hydrodynamic equations of motion with shear and bulk coupled together at finite µB for both DNMR and phenomenological Israel-Stewart equations of motion and discuss their influence on potential attractors at finite µ B and their corresponding {T, µ B } trajectories.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Properties of the QCD matter: review of selected results from the relativistic heavy ion collider beam energy scan (RHIC BES) program

In the paper, we discuss the development of the multigap resistive plate chamber time-of-flight (TOF) technology and the production of the solenoidal tracker at RHIC (STAR) TOF detector in China at the beginning of the twenty-first century. Subsequently, recent experimental results from the first beam energy scan program (BES-I) at the Relativistic Heavy Ion Collider (RHIC) pertaining to measurements of collectivity, chirality, criticality, global polarization, strangeness, heavy flavor, dilepton and light nuclei productions are reviewed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Searching for Parton Energy Loss in Quark-Gluon Plasma Droplets (Technical Report)

This technical report summarizes the main accomplishments of the research performed under the U.S. Department of Energy (DOE) Office of Science, Early Career Award (ECA), grant number DE-SC0018117, from 9/1/2017 to 8/31/2022, with Prof. Dennis Perepelitsa as the single PI. The grant proposal was to investigate the quark-gluon plasma (QGP) created in ultrarelativistic collisions of large nuclei with the ATLAS experiment at the Large Hadron Collider (LHC) and to prepare for this physics with the sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). In particular, the focus was on QGP regions of different sizes and shapes, including the tradtional “large” collision systems such as Pb+Pb as well as small collision systems such as p+Pb, where there has been evidence of QGP “flow” but not yet the accompanying energy loss from hard-scattered partons traversing the QGP medium. Additionally, a particular tool was the use of photon+jet events, where the photon is unaffected by the QGP and thus serves as the “control” while the jet (the result of parton fragmentation) is the “probe” of the QGP. The research was successfully carried out, resulting in over ten publications of experimental measurements in peer-reviewed journals, and the significant training of junior scientists.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Possible octupole deformation of 208 Pb and the ultracentral v 2 to v 3 puzzle

Recent measurements have established the sensitivity of ultracentral heavy-ion collisions to the deformation parameters of nonspherical nuclei. In the case of 129 Xe collisions, a quadrupole deformation of the nuclear profile led to an enhancement of elliptic flow in the most central collisions. In 208 Pb collisions a discrepancy exists in similar centralities, where either elliptic flow is overpredicted or triangular flow is underpredicted by hydrodynamic models; this is known as the v 2 -to-v 3 puzzle in ultracentral collisions. Motivated by low-energy nuclear structure calculations, we consider the possibility that 208Pb nuclei could have a pear-shape deformation (octupole), which has the effect of increasing triangular flow in central PbPb collisions. Using the recent data from ALICE and ATLAS, we reexamine the v 2 -to-v 3 puzzle in ultracentral collisions, including new constraints from recent measurements of the triangular cumulant ratio v 3 {4}/v 3 {2} and comparing two different hydrodynamic models. We find that while an octupole deformation would slightly improve the ratio between v 2 and v 3 , it is at the expense of a significantly worse triangular flow cumulant ratio. In fact, the latter observable prefers no octupole deformation, with β 3 ≲ 0.0375 for 208 Pb, and is therefore consistent with the expectation for a doubly-magic nucleus even at top collider energies. Furthermore, the v 2 -to-v 3 puzzle remains a challenge for hydrodynamic models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Comparing pion production in transport simulations of heavy-ion collisions at 270⁢𝐴 MeV under controlled conditions

Within the TMEP, we present a detailed study of the performance of different transport models in Sn+Sn collisions at 270A MeV, and put particular emphasis on the production of pions and Delta resonances, which have been used as probes of the nuclear symmetry energy. We prescribe a common and rather simple physics model, and follow in detail the results of 4 BUU models and 6 QMD models. The nucleonic evolution of the collision and the nucleonic observables in these codes do not completely converge, but the differences among the codes can be understood as being due to several reasons: the basic differences between BUU and QMD models in the representation of the phase-space distributions, computational differences in the mean-field evaluation, and differences in the adopted strategies for the Pauli blocking in the collision integrals. For pionic observables, we find that a higher maximum density leads to an enhanced pion yield and a reduced pi- pi+ yield ratio, while a more effective Pauli blocking generally leads to a slightly suppressed pion yield and an enhanced pi- pi+ yield ratio. We specifically investigate the effect of the Coulomb force, and find that it increases the total pi- pi+ yield ratio but reduces the ratio at high pion energies, although differences in its implementations do not have a dominating role in the differences among the codes. Taking into account only the results of codes that strictly follow the homework specifications, we find a convergence of the codes in the final charged pion yield ratio to a 1 sigma deviation of about 5%. Furthermore, the uncertainty is expected to be reduced to about 1.6% if the same or similar strategies and ingredients, i.e., an improved Pauli blocking and calculation of the non-linear term in the mean-field potential, are similarly used in all codes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Coulomb field correction due to virtual $e$ + $e$ - production in heavy ion collisions

The correction to the Coulomb energy due to virtual production of $e$ + $e$ - pairs, which is on the order of one percent of the Coulomb energy at nuclear scales is discussed. The effects of including a pair-production term in the semi-empirical mass formula and the correction to the Coulomb barrier for a handful of nuclear collisions using the Bass and Coulomb potentials are studied. Furthermore, with an eye toward future work using Constrained Molecular Dynamics (CoMD) model, we also calculate the correction to the Coulomb energy and force between protons after folding with a Gaussian spatial distribution.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

The QCD phase diagram and Beam Energy Scan physics: A theory overview

Herein we review recent theoretical developments relevant to heavy-ion experiments carried out within the Beam Energy Scan program at the Relativistic Heavy Ion Collider. Our main focus is on the description of the dynamics of systems created in heavy-ion collisions and establishing the necessary connection between the experimental observables and the QCD phase diagram.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Reaction dynamics and in-medium nucleon-nucleon cross section with 12 C+ 1 H at 95 MeV/nucleon

Reaction dynamics and effective in-medium nucleon-nucleon (NN) cross section are studied, using the antisymmetrized molecular dynamics (AMD) model with one of the simplest heavy ion collisions, 12 C+ ⁢1 H. The roles of different stochastic processes are studied, which are installed in the original AMD. One is the diffusion process as a part of the quantum fluctuation originated from the Fermi motion during the time evolution of the wave packets in the mean field (AMD/D). The second is a coalescence treatment for light clusters with A ≤ 8 (AMD/D-COALS). The third is the collision process, installed in AMD with different form of the in-medium NN cross sections. These different processes are examined, using the experimental angular distributions and energy spectra of light charged particles and intermediate mass fragments. The effective in-medium NN cross sections are evaluated from the simulated AMD events and compared with the experimentally extracted values. A good agreement is obtained between the AMD values from the 12 C + 1 H reaction at 95 MeV/nucleon and the experimental results for nuclear matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Chemical freeze-out parameters of net-kaons in heavy-ion collisions

In this work, we study chemical freeze-out parameters for heavy-ion collisions by performing two different thermal analyses. We analyze results from thermal fits for particle yields, as well as, net-charge fluctuations in order to characterize the chemical freeze-out. The Hadron Resonance Gas (HRG) model is employed for both methods. By separating the light hadrons from the strange hadrons in thermal fits, we study the proposed flavor hierarchy. For the net-charge fluctuations, we calculate the mean-over-variance ratio of the net-kaon fluctuations in the HRG model at the five highest energies of the RHIC Beam Energy Scan (BES) for different particle data lists. We compare these results with recent experimental data from the STAR collaboration in order to extract sets of chemical freeze-out parameters for each list. We focused on particle lists which differ largely in the number of resonant states. By doing so, our analysis determines the effect of the amount of resonances included in the HRG model on the freeze-out conditions. Our findings have potential impact on various other models in the field of relativistic heavy ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Measurements of azimuthal anisotropy of nonprompt D 0 mesons in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Measurements of the elliptic ($v$ 2 ) and triangular ($v$ 3 ) azimuthal anisotropy coefficients are presented for D 0 mesons produced in b hadron decays (nonprompt D 0 mesons) in lead-lead collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt D 0 mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb –1 . Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt D 0 mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of $v$ 2 and $v$ 3 and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt D 0 mesons. The results are in agreement with theoretical predictions that include a mass dependence in the interactions of quarks with the medium

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗