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Nuclear Theory·nucl-th

Wednesday·November 30, 2022

14 papers—6 primary·8 cross-listed

All14Primary6Cross-lists8
  1. 01

    [Submitted on 28 Nov 2022]

    Directed flow in a baryonic fireball

    Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳

    Directed flow of identified hadrons in a baryon rich fireball is an interesting observable as it is expected to probe several physics aspects: the initial three dimensional baryon profile in the thermalised fireball that can be treated as an input for the hydrodynamic evolution, the nature of baryon dissipation current and baryon transport coefficients, the QCD equation of state at finite baryon densities as well as the nature of phase transition between the quark gluon and hadronic phases. Particularly, the mid-rapidity slope of the rapidity dependence of directed flow of protons have been proposed as a sensitive observable to several of these physics aspects while a consistent description of the splitting in directed flow of baryon and its anti-particle has been a challenge. In this work, we propose a suitable ansatz of the initial condition for baryon deposition. When such a baryon deposition ansatz is coupled to a tilted fireball, we manage to find parameter space that can describe the directed flow of identified hadrons including the elusive baryon antibaryon splitting of directed flow. Further, we demonstrate that future measurements of baryon antibaryon directed flow at larger rapidities have the potential to constrain the baryon diffusion coefficient.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2211.15729 [pdf]
    12 citations
  2. 02

    [Submitted on 29 Nov 2022]

    QRPA calculations for M1 transitions with the noniterative finite amplitude method and the application to neutron radiative capture cross sections

    Hirokazu Sasaki · Toshihiko Kawano · Ionel Stetcu

    We derive the equations of quasiparticle random-phase approximation (QRPA) based on the finite amplitude method (FAM) with the Hartree-Fock+BCS (HF+BCS) single-particle states, and calculate the magnetic dipole (M1) transition for deformed gadolinium isotopes. Our QRPA calculation shows both large spin-flip transitions in the 5 to 10 MeV excitation energy and the low energy orbital transition that would correspond to the M1 scissors mode observed in nuclear experiments. Then, we calculate neutron capture reactions based on the statistical Hauser-Feshbach theory with the photoabsorption cross sections given by QRPA. We find that the capture cross section is enhanced due to the contribution from the low energy M1 transition although the calculated capture cross section still underestimates the experimental data. This issue in the calculated capture cross section could be improved by uncertainties of low energy E1 transition neglected in our QRPA calculation.

    Comments:
    9 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2211.15935 [pdf]
    PRC(2023)·8 citations
  3. 03

    [Submitted on 29 Nov 2022]

    Normal ordering of three-nucleon interactions for ab initio calculations of heavy nuclei

    K. Hebeler · V. Durant · J. Hoppe · M. Heinz · A. Schwenk · J. Simonis · A. Tichai

    Three-nucleon (3N) interactions are key for an accurate solution of the nuclear many-body problem. However, fully taking into account 3N forces constitutes a computational challenge and hence approximate treatments are commonly employed. The method of normal ordering has proven to be a powerful tool that allows to systematically include 3N interactions in an efficient way, but traditional normal-ordering frameworks require the representation of 3N interactions in a large single-particle basis, typically necessitating a truncation of 3N matrix elements. While this truncation has only a minor impact for light and medium-mass nuclei, its effects become sizable for heavier systems and hence limit the scope of \textit{ab initio} calculations. In this work, we present a novel normal-ordering framework that allows to circumvent this limitation by performing the normal ordering directly in a Jacobi basis. We discuss in detail the new framework, benchmark it against established results, and present calculations for ground-state energies and charge radii of heavy nuclei, such as Sn and Pb.

    Comments:
    13 pages, 9 figures, 2 tables, published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2211.16262 [pdf]
    PRC(2023)·47 citations
  4. 04

    [Submitted on 29 Nov 2022]

    The 3D structure of anisotropic flow in small collision systems at the Relativistic Heavy Ion Collider

    Wenbin Zhao🇺🇸 · Sangwook Ryu🇺🇸 · Chun Shen🇺🇸 · Björn Schenke🇺🇸

    We present (3+1)D dynamical simulations of asymmetric nuclear collisions at the Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the RHIC small system scan at 200 GeV center of mass energy. We calibrate parameters to describe central He+Au collisions and make extrapolations to d+Au and p+Au collisions. Our calculations demonstrate that approximately 50% of the difference between the measurements by the STAR and PHENIX Collaborations can be explained by the use of reference flow vectors from different rapidity regions. This emphasizes the importance of longitudinal flow decorrelation for anisotropic flow measurements in asymmetric nuclear collisions, and the need for (3+1)D simulations. We also present results for the beam energy dependence of particle spectra and anisotropic flow in d+Au collisions.

    Comments:
    Include the STAR new data, and include the statistical error and systematic error
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2211.16376 [pdf]
    PRC(2023)·60 citations
  5. 05

    [Submitted on 29 Nov 2022]

    Probing initial baryon stopping and equation of state with rapidity-dependent directed flow of identified particles

    Lipei Du🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    Using a (3+1)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving Au+Au collisions are considered, performed at ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudo-rapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of for both mesons and baryons. We find that the of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the dense nuclear matter at finite chemical potentials.

    Comments:
    v1: 6+3 pages, 4 figures; v2: add discussion on the Lund string model
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2211.16408 [pdf]
    PRC(2023)·42 citations
  6. 06

    [Submitted on 29 Nov 2022]

    Lee-Yang-inspired functional including contributions to fourth order in effective field theory

    Jérémy Bonnard🇫🇷

    In the last years, a new family of energy density functionals directly inspired by effective field theory (EFT) has been developed, among which the ELYO (extended Lee-Yang Orsay) functional. In this paper, a new extension of ELYO that includes the recently calculated fourth-order EFT terms is presented. Compared to the previous version, the description of neutron-drop energies slightly degrades for a harmonic trap MeV -- yet remaining reasonable -- , but improves for MeV. Furthermore, the obtained neutron effective mass agrees significantly better with \textit{ab-initio} estimates.

    Comments:
    6 pages, 3 figures, 2 tables. Contribution to the proceedings of the 28th International Nulcear Physics Conference 2022, Cape Town, South Africa 11 to 16 September 2022
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2211.16447 [pdf]
    J.Phys.Conf.Ser.(2023)·0 citations

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first authorsco-authorsvia INSPIRE