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Nuclear Theory·nucl-th

Friday·October 27, 2023

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    Probing spin and pseudospin symmetries in deformed nuclei by the Green's function method

    Ting-Ting Sun · Bing-Xin Li · Kun Liu

    (Pseudo)spin symmetries play vital roles in nuclear physics and have been studied extensively in spherical nuclei. In this work, possible spin and pseudospin symmetries in deformed nuclei are examined by solving a coupled-channel Dirac equation with quadruple deformation. The Green's function method is taken which provides a novel way to exactly determine the single-particle levels and properly describe the spacial density distributions. Taking axially-deformed nucleus Dy as an example, the spin doublets with a combination of Nilsson levels and pseudospin doublets with a combination of are determined. Different behaviors are displayed for the spin and pseudospin doublets. For the spin partners, those with smaller angular momentum and the third component owns better symmetry such as the doublet while good pseudospin symmetry appears in partners locating close to the continuum threshold. By examining the single-particle Nilsson levels and the energy splittings between the partners, the conservation and breaking of SS and PSS are examined at different deformations. In the prolate side, the Nilsson levels for the spin and pseudospin doublets are almost parallel and the energy splittings are stable against varying deformations. By examining the density distributions, great similarities have been observed in the upper components for the spin doublets while great similarities in the lower component for the pseudospin doublets. Besides, these similarities maintain well at different deformations.

    nucl-thPRC(2024)·6 citations
  2. 02

    Baryon density dependence of viscosities of the quark-gluon plasma at hadronization

    Zhidong Yang🇨🇳 · Yifeng Sun🇨🇳 · Lie-Wen Chen🇨🇳

    The meson and baryon provide unique probes of the properties of the quark-gluon plasma (QGP) at hadronization in relativistic heavy-ion collisions. Using the quark recombination model with the quark phase-space information parameterized in a viscous blastwave, we perform Bayesian inference of the shear and bulk viscosities of the QGP at hadronization with a temperature of MeV by analyzing the and data in Au+Au collisions at 19.6-200 GeV and Pb+Pb collisions at 2.76 TeV, corresponding to a baryon chemical potential variation from (at TeV) to MeV (at GeV). We find that the shear viscosity to enthalpy ratio of the QGP at hadronization decreases as increases, with at and at MeV, while the corresponding specific bulk viscosity is essentially constant with for MeV. Our results suggest that the QGP at hadronization ( MeV) with finite baryon density is more close to perfect fluid than that with zero baryon density.

    nucl-thastro-ph.HEhep-phnucl-exPRC(2024)·4 citations
  3. 03

    Applications of emulation and Bayesian methods in heavy-ion physics

    Jean-François Paquet🇺🇸

    Heavy-ion collisions provide a window into the properties of many-body systems of deconfined quarks and gluons. Understanding the collective properties of quarks and gluons is possible by comparing models of heavy-ion collisions to measurements of the distribution of particles produced at the end of the collisions. These model-to-data comparisons are extremely challenging, however, because of the complexity of the models, the large amount of experimental data, and their uncertainties. Bayesian inference provides a rigorous statistical framework to constrain the properties of nuclear matter by systematically comparing models and measurements. This review covers model emulation and Bayesian methods as applied to model-to-data comparisons in heavy-ion collisions. Replacing the model outputs (observables) with Gaussian process emulators is key to the Bayesian approach currently used in the field, and both current uses of emulators and related recent developments are reviewed. The general principles of Bayesian inference are then discussed along with other Bayesian methods, followed by a systematic comparison of seven recent Bayesian analyses that studied quark-gluon plasma properties, such as the shear and bulk viscosities. The latter comparison is used to illustrate sources of differences in analyses, and what it can teach us for future studies.

    nucl-thJ.Phys.G(2024)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE