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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Modeling of heavy-flavor pair correlations in Au-Au collisions at 200 A GeV at the BNL Relativistic Heavy Ion Collider

In this paper, we study the nuclear modification of angular and momentum correlations between heavy quark pairs in ultrarelativistic heavy-ion collisions. The evolution of heavy quarks inside the thermalized medium is described via a modified Langevin approach that incorporates both elastic and inelastic interactions with the medium constituents. The spacetime evolution of the fireball is obtained from a (2+1)-dimensional viscous hydrodynamics simulation. The hadronization of heavy quarks is performed by utilizing a hybrid model of fragmentation and coalescence. Our results show that the nuclear modification of the transverse momentum imbalance of D $\overline{D}$ pairs reflects the total energy loss experienced by the heavy quarks and may help us probe specific regions of the medium. The angular correlation of heavy-flavor pairs, especially in the low- to intermediate-transverse-momentum regime, is sensitive to the detailed energy-loss mechanism of heavy quarks inside the quark-gluon plasma.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Measurement of elliptic flow of light nuclei at s N N = 200 , 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV at the BNL Relativistic Heavy Ion Collider

Here we present measurements of second-order azimuthal anisotropy ( v 2 ) at midrapidity ( |y| < 1.0 ) for light nuclei d , t , 3 He (for $\sqrt{s}$$_{NN}$ = 200 , 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and antinuclei$\bar{d}$ ( $\sqrt{s}$$_{NN}$ = 200 , 62.4, 39, 27, and 19.6 GeV) and 3 ¯¯¯¯¯ He ( $\sqrt{s}$$_{NN}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The v 2 for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{p}$. We observe mass ordering in nuclei v 2 ( p T ) at low transverse momenta ( p T < 2.0 GeV/c). We also find a centrality dependence of v 2 for d and $\bar{d}$ . The magnitude of v 2 for t and 3 He agree within statistical errors. Light-nuclei v 2 are compared with predictions from a blast-wave model. Atomic mass number ( A ) scaling of light-nuclei v 2 (p T ) seems to hold for p T / A < 1.5 GeV/c . Results on light-nuclei v 2 from a transport-plus-coalescence model are consistent with the experimental measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Measurement of the H Λ 3 lifetime in Au+Au collisions at the BNL Relativistic Heavy Ion Collider [Measurement of the H Λ 3 lifetime in Au+Au collisions at the Relativistic Heavy Ion Collider]

Here, an improved measurement of the 3 Λ H lifetime is presented. In this paper, the mesonic decay modes 3 Λ H → 3 He + π – and 3 Λ H → d + p + π – are used to reconstruct the 3 Λ H from Au+Au collision data collected by the STAR collaboration at Relativistic Heavy Ion Collider (RHIC). A minimum χ2 estimation is used to determine the lifetime of τ = 142 +24 –21 (stat.) ± 29 (syst.) ps. This lifetime is about 50% shorter than the lifetime τ = 263 ± 2 ps of a free Λ, indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R. ( 3 He+π – )/( B.R. ( 3 He+π – ) + B.R. (d+p+π – ) ) = 0.32 ± 0.05 (stat.) ± 0.08 (syst.). Our ratio result favors the assignment J( 3 Λ H) = 1/2 over J( 3 Λ H) = 3/2. These measurements will help to constrain models of hyperon-baryon interactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Harmonic decomposition of three-particle azimuthal correlations at energies available at the BNL Relativistic Heavy Ion Collider

Here, we present measurements of three-particle correlations for various harmonics in Au+Au collisions at energies ranging from √ s NN=7.7 to 200 GeV using the STAR detector. The quantity < cos(mΦ 1 +nΦ 2 –(m+n)Φ 3 ) >, with Φ being the azimuthal angles of the particles is evaluated as a function of √ s NN, collision centrality, transverse momentum, p T , pseudorapidity difference, Δη, and harmonics (m and n). These data provide detailed information on global event properties such as the three-dimensional structure of the initial overlap region, the expansion dynamics of the matter produced in the collisions, and the transport properties of the medium. A strong dependence on Δη is observed for most harmonic combinations, which is consistent with breaking of longitudinal boost invariance. An interesting energy dependence is observed when one of the harmonics m,n, or m+n is equal to two, for which the correlators are dominated by the two-particle correlations relative to the second-harmonic event plane. These measurements can be used to constrain models of heavy-ion collisions over a wide range of temperature and baryon chemical potential.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Examination of the observability of a chiral magnetically driven charge-separation difference in collisions of the Ru 44 96 + Ru 44 96 and Zr 40 96 + Zr 40 96 isobars at energies available at the BNL Relativistic Heavy Ion Collider

Here, anomalous viscous fluid dynamics model calculations for Ru 44 96 + Ru 44 96 and Zr 40 96 + Zr 40 96 collisions ( s N N = 200 GeV) are used in concert with a charge-sensitive correlator to test its ability to detect and characterize the charge separation difference expected from the chiral magnetic effect (CME) in these isobaric collisions. The tests indicate a larger charge separation for Ru 44 96 + Ru 44 96 than for Zr 40 96 + Zr 40 96 collisions and a discernible CME-driven difference of ~ 10 % in the presence of realistic non-CME backgrounds. Furthermore, they suggest a strategy for evaluating the relative influence of the background correlations, present for each isobar. These results suggest that charge-separation measurements for these isobaric species could serve to further constrain unambiguous identification and characterization of the CME in upcoming measurements at the Relativistic Heavy Ion Collider

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Collision-energy dependence of p t correlations in Au + Au collisions at energies available at the BNL Relativistic Heavy Ion Collider

We present two-particle $p_{\rm t}$ correlations as a function of event centrality for Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV show a power law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at $\sqrt{s_{\rm NN}} = 2.76~ {\rm TeV}$ from ALICE. As the collision energy is lowered from $\sqrt{s_{\rm NN}}$ = 200 GeV to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to $\sqrt{s_{\rm NN}}$ = 200 GeV in contrast to previous measurements that showed little dependence on the collision energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Beam energy dependence of (anti-)deuteron production in Au + Au collisions at the BNL Relativistic Heavy Ion Collider

Here, we report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $ \sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at RHIC. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter B 2 are discussed. We find that the values of B 2 for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at $ \sqrt{s_{NN}}$ from 19.6 to 39 GeV. In addition, values of B 2 are found to vary with collision energy and show a broad minimum around $ \sqrt{s_{NN}}$ = 20 to 40 GeV, which might imply a change of the equation of state of the medium in these collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗