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Nuclear Theory·nucl-th

Thursday·September 30, 2021

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 01

    [Submitted on 28 Sept 2021]

    Systematical studies of the E1 photon strength functions combining Skyrme-HFB+QRPA model and experimental giant dipole resonance properties

    Y. Xu🇷🇴 · S. Goriely🇧🇪 · E. Khan🇫🇷

    Valuable theoretical predictions of nuclear dipole excitations in the whole nuclear chart are of great interest for different applications, including in particular nuclear astrophysics. We present here the systematic study of the electric dipole (E1) photon strength functions (PSFs) combining the microscopic Hartree-Fock-Bogoliubov plus Quasiparticle Random Phase Approximation (HFB+QRPA) model and the parametrizations constrained by the available experimental giant dipole resonance (GDR) data. For about 10000 nuclei with 8<Z<124 lying between the proton and the neutron drip-lines on nuclear chart, the particle-hole strength distributions are computed using the HFB+QRPA model under the assumption of spherical symmetry and making use of the BSk27 Skyrme effective interaction derived from the most accurate HFB mass model (HFB-27) so far achieved. Large-scale calculations of the BSk27+QRPA E1 PSFs are performed in the framework of a specific folding procedure, in which three phenomenological improvements are considered. First, two interference factors are introduced and adjusted to reproduce at best the available experimental GDR data. Second, an empirical expression accounting for the deformation effect is applied to describe the peak splitting of the strength function. Third, the width of the strength function is corrected by a temperature-dependent term, which effectively increases the de-excitation photon strength function at low-energy. The E1 PSFs as well as the extracted GDR peaks and widths are compared with available experimental data. A relatively good agreement with data indicates the reliability of the calculations. Eventually, the astrophysical (n,g) rates for all the 10000 nuclei with 8<Z<124 are estimated using the present E1 PSFs. The resulting reaction rates are compared with previous BSk7+QRPA results and Gogny-HFB+QRPA predictions based on the D1M interaction.

    Comments:
    16 pages, 14 figures, to be published on Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
    arXiv:
    2109.13968 [pdf]
    PRC(2021)·18 citations
  2. 02

    [Submitted on 28 Sept 2021]

    Gaussian process error modeling for chiral effective-field-theory calculations of at low energies

    Bijaya Acharya🇩🇪 · Sonia Bacca🇩🇪

    We calculate the energy-dependent cross section of the process in chiral effective field theory and apply state-of-the-art tools for quantification of theory uncertainty. We focus on the low-energy regime, where the magnetic dipole and the electric dipole transitions cross over, including the range relevant for big-bang nucleosynthesis. Working with the leading one- and two-body electromagnetic currents, we study the order-by-order convergence of this observable in the chiral expansion of the nuclear potential. We find that the Gaussian process error model describes the observed convergence very well, allowing us to present Bayesian credible intervals for the truncation error with correlations between the cross sections at different energies taken into account. We obtain a 1 estimate of about 0.2\% for the uncertainty from the truncation of the nuclear potential. This is an important step towards calculations with statistically interpretable uncertainties for astrophysical reactions involving light nuclei.

    Subjects:
    Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
    arXiv:
    2109.13972 [pdf]
    PLB(2022)·22 citations
  3. 03

    [Submitted on 29 Sept 2021]

    The sixth order cumulant of net-proton number in Binomial distribution at 200 GeV

    Li-Zhu Chen🇨🇳 · Ye-Yin Zhao🇨🇳 · Jin Wu🇨🇳 · Zhi-Ming Li🇨🇳 · Yuan-Fang Wu🇨🇳

    It is proposed that ratios of the sixth order to the second order cumulant () of conserved quantities are sensitive to the chiral crossover transition. Recently, the negative was obtained both in theoretical Lattice QCD and experiments at 200 GeV. In this study, we investigate the behavior of net-proton in statistical Binomial distribution (BD) at 200 GeV in Au + Au collisions. With the BD parameters extracted from RHIC/STAR, it is found that can be negative. Furthermore, the obtained becomes smaller when applying the same magnitude of experimental statistics and calculation method to simulations. In 0-10\% centrality, there is a significant difference between the simulated result and theoretical expectation. Based on the extracted parameters and experimentally collected statistics, the baseline of net-proton in BD is presented.

    Comments:
    8 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2109.14169 [pdf]
    CPC(2021)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE