PaperPanorama
FAQ

Nuclear Theory·nucl-th

Tuesday·February 28, 2023

16 papers—4 primary·12 cross-listed

All16Primary4Cross-lists12
  1. 01

    [Submitted on 27 Feb 2023]

    Evidence of Hexadecapole Deformation in Uranium-238 at the Relativistic Heavy Ion Collider

    Wouter Ryssens🇧🇪 · Giuliano Giacalone🇩🇪 · Björn Schenke🇺🇸 · Chun Shen🇺🇸

    There is strong evidence of the failure of hydrodynamic simulations of the quark-gluon plasma (QGP) to reproduce data on the elliptic flow of particles in relativistic collisions of U nuclei at the BNL Relativistic Heavy Ion Collider (RHIC). We demonstrate that this failure is caused by an inappropriate implementation of well-deformed ions, such as U, in the hydrodynamic framework. Past studies have identified the deformation of the nuclear surface with that of the nuclear volume, though these are different concepts. In particular, a volume quadrupole moment can be generated by both a surface hexadecapole and a surface quadrupole moment. This feature was so far neglected in the modeling of heavy-ion collisions, and is particularly relevant for nuclei like U, which is both quadrupole- and hexadecapole-deformed. With rigorous input from Skyrme density functional calculations, we show that correcting for such effects in the implementation of nuclear deformations in hydrodynamic simulations restores agreement with BNL RHIC data. This brings consistency to the results of nuclear experiments across energy scales, and demonstrates the impact of the hexadecapole deformation of U on high-energy collisions.

    Comments:
    7 pages, 2 figures; supplementary material contains best-fit Woods-Saxon parameters for 197Au and 238U
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2302.13617 [pdf]
    PRL(2023)·90 citations
  2. 02

    [Submitted on 27 Feb 2023]

    Rapidity scan with multistage hydrodynamic and statistical thermal models

    Lipei Du🇨🇦 · Han Gao🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    We calibrate a (3+1)-dimensional multistage hybrid framework using the measured pseudo-rapidity distribution of charged particles and rapidity distribution of net protons for central Au+Au collisions at GeV. We then study the thermodynamic properties of the nuclear matter along the beam direction, and the phase diagram regions probed by the hadronization process near the chemical freeze-out. Using the rapidity-dependent thermal yields of identified particles with full rapidity coverage from the hybrid framework, we apply different scenarios of the statistical thermal model to extract the thermodynamic parameters at the freeze-out, with the known system properties from the hybrid model as a closure test. We find significant theoretical uncertainties in the thermal models when applied to regions away from midrapidity. We also propose a thermal model inspired by the hybrid approach that includes thermal smearing and longitudinal flow for the nuclear matter created at low beam energies.

    Comments:
    v1: 17 pages, 12 figures; v2: structure mainly adjusted in Sec. IIB, results remain unchanged
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2302.13852 [pdf]
    PRC(2024)·27 citations
  3. 03

    [Submitted on 27 Feb 2023]

    Decoding the flow evolution in Au+Au reactions at GeV using hadron flow correlations and dileptons

    Tom Reichert🇩🇪 · Oleh Savchuk🇩🇪 · Apiwit Kittiratpattana🇩🇪 · Pengcheng Li🇨🇳 · Jan Steinheimer🇩🇪 · Mark Gorenstein🇩🇪 · Marcus Bleicher🇩🇪

    We investigate the development of the directed, , and elliptic flow, , in heavy ion collisions in mid-central Au+Au reactions at GeV. We demonstrate that the elliptic flow of hot and dense matter is initially positive () due to the early pressure gradient. This positive transfers its momentum to the spectators, which leads to the creation of the directed flow . In turn, the spectator shadowing of the in-plane expansion leads to a preferred decoupling of hadrons in the out-of-plane direction and results in a negative for the observable final state hadrons. We propose a measurement of flow correlations and of the elliptic flow of dileptons as methods to pin down this evolution pattern. The elliptic flow of the dileptons allows then to determine the early-state EoS more precisely, because it avoids the strong modifications of the momentum distribution due to shadowing seen in the protons. This opens the unique opportunity for the HADES and CBM collaborations to measure the Equation-of-State directly at 2-3 times nuclear saturation density.

    Comments:
    8 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2302.13919 [pdf]
    PLB(2023)·19 citations
  4. 04

    [Submitted on 27 Feb 2023]

    Methods for systematic study of nuclear structure in high-energy collisions

    Matthew Luzum🇧🇷 · Mauricio Hippert🇺🇸 · Jean-Yves Ollitrault🇫🇷

    There is increasing interest in using high-energy collisions to probe the structure of nuclei, in particular with the high-precision data made possible by collisions performed with pairs of isobaric species. A systematic study requires a variation of parameters representing nuclear properties such as radius, skin thickness, angular deformation, and short-range correlations, to determine the sensitivity of the various observables on each of these properties. In this work we propose a method for efficiently carrying out such study, based on the shifting of positions of nucleons in Monte-Carlo samples. We show that by using this method, statistical demands can be dramatically reduced -- potentially reducing the required number of simulated events by orders of magnitude -- paving the way for systematic study of nuclear structure in high-energy collisions,

    Comments:
    13 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2302.14026 [pdf]
    EPJA(2023)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE