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Nuclear Theory·nucl-th

Friday·October 4, 2024

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    Role of neutron pairing with density-gradient dependence in the semi-microscopic treatment of the inner crust of neutron stars

    Nicolas Chamel · John-Michael Pearson · Nikolay N. Shchechilin

    Using the fourth-order extended Thomas-Fermi method with Strutinsky-integral shell and pairing corrections, we calculate the inner crust of neutron stars with the BSk31 functional, whose pairing has two terms: i) a term that is fitted to the results of microscopic calculations on homogeneous nuclear matter (accounting for both medium polarization and self-energy effects) that are more realistic than those of our earlier functionals; ii) an empirical term that is dependent on the density gradient, which permits an excellent fit to nuclear masses. Both proton and neutron pairing are taken into account, the former in the BCS theory and the latter in the local density approximation. We found that the equilibrium value of the proton number remains 40 over the entire density range considered, whether or not neutron pairing is included. The new equation of state and the composition are very similar to those of our previously preferred functional, BSk24. However, the predicted neutron pairing fields are quite different. In particular, clusters are found to be impermeable to the neutron superfluid. The implications for the neutron superfluid dynamics are briefly discussed. Since the new pairing is more realistic, the functional BSk31 is better suited for investigating neutron superfluidity in neutron-star crusts.

    nucl-thastro-ph.HEPRC(2024)·9 citations
  2. 02

    On the extraction of fission mode properties from fragment mass distributions

    Patrick McGlynn · Cedric Simenel

    Background: Fission modes are typically characterised by fragment mass and total kinetic energy centroids, around which a distribution of these variables is observed. These distributions are usually fitted with Gaussian functions. Purpose: To investigate how the properties of these ``Gaussian fission modes'' compare with underlying ``theoretical fission modes'' defined from the potential energy surface of the fissioning nuclei. Methods: A simple approach, inspired by the scission point model, is introduced to investigate the impact of anharmonicity of the potential along the scission line on Gaussian mode properties. This approach is also used to evaluated an ``effective potential'' from the yields. Results: Several Gaussian functions are usually required to fit yields from non-harmonic potentials associated with a unique theoretical mode. Similarly, ``effective fission modes'', defined from the wells of the effective potentials, are sometime very different to the Gaussian modes. For instance, the S1 and S2 Brosa modes contribute to the same effective potential well at scission. Conclusions: Gaussian fits are useful to identify the role of shell effects in fission. However, comparisons with theoretical potential energy surfaces are better carried with effective potentials extracted from the yields, assuming that a broad range of excitation energies is available.

    nucl-thPRC(2025)·3 citations
  3. 03

    Simulating collectivity in dense baryon matter with multiple fluids

    Iurii Karpenko🇨🇿 · Jakub Cimerman🇨🇿 · Pasi Huovinen🇵🇱 · Boris Tomasik🇨🇿

    We report on construction of a modern multi-fluid approach to heavy-ion collisions at FAIR/BES energies (MUFFIN) and show the reproduction of basic experimental observables in Au-Au collisions in the RHIC Beam Energy Scan program. We also show the -differential and -integrated polarization of (anti-) hyperons. In MUFFIN simulations, we observe a strong splitting between polarizations of and anti-. The splitting is driven purely by a finite baryon chemical potential.

    nucl-thnucl-exEPJ Web Conf.(2025)·1 citation
  4. 04

    Accurate calculation of low energy scattering phase shifts of charged particles in a harmonic oscillator trap

    Mirko Bagnarol · Nir Barnea · Matus Rojik · Martin Schafer

    Considering the elastic scattering of two charged particles, we present two methods for numerically solving the generalized Coulomb-corrected BERW formula with high accuracy across the entire energy spectrum. We illustrate these methods using p-alpha scattering, employing a phenomenological p-alpha short-range interaction. Our results reproduce the phase shifts computed with the Numerov method for all l=0 and l=1 channels. We also provide full access to the Python script used to obtain these results, which can be readily applied to a wide range of core-fragment scattering problems in nuclear and atomic physics.

    nucl-thphysics.chem-phPLB(2025)·5 citations

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first authorsco-authorsvia INSPIRE