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Nuclear Theory·nucl-th

Tuesday·October 27, 2020

16 papers—6 primary·10 cross-listed

All16Primary6Cross-lists10
  1. 01

    [Submitted on 23 Oct 2020]

    Spin Susceptibility in Neutron Matter from Quantum Monte Carlo Calculations

    Luca Riz · Francesco Pederiva · Diego Lonardoni · Stefano Gandolfi

    The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions include both the phenomenological Argonne AV8+UIX potential and local interactions that are derived from chiral effective field theory up to next-to-next-to-leading order.

    Comments:
    15 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.12680 [pdf]
    Particles(2020)·5 citations
  2. 02

    [Submitted on 23 Oct 2020]

    Machine learning-based inversion of nuclear responses

    Krishnan Raghavan🇺🇸 · Prasanna Balaprakash🇺🇸 · Alessandro Lovato🇺🇸 · Noemi Rocco🇺🇸 · Stefan M. Wild🇺🇸

    A microscopic description of the interaction of atomic nuclei with external electroweak probes is required for elucidating aspects of short-range nuclear dynamics and for the correct interpretation of neutrino oscillation experiments. Nuclear quantum Monte Carlo methods infer the nuclear electroweak response functions from their Laplace transforms. Inverting the Laplace transform is a notoriously ill-posed problem; and Bayesian techniques, such as maximum entropy, are typically used to reconstruct the original response functions in the quasielastic region. In this work, we present a physics-informed artificial neural network architecture suitable for approximating the inverse of the Laplace transform. Utilizing simulated, albeit realistic, electromagnetic response functions, we show that this physics-informed artificial neural network outperforms maximum entropy in both the low-energy transfer and the quasielastic regions, thereby allowing for robust calculations of electron scattering and neutrino scattering on nuclei and inclusive muon capture rates.

    Comments:
    12 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.12703 [pdf]
    PRC(2021)·31 citations
  3. 03

    [Submitted on 24 Oct 2020]

    Coupled-channels treatment of in effective field theory

    Renato Higa🇧🇷 · Pradeepa Premarathna🇺🇸 · Gautam Rupak🇺🇸

    The E1 and M1 contributions to at low energies are calculated in halo effective field theory. The excited core is included as an explicit degree of freedom in a coupled-channels calculation. The E1 transition is calculated up to next-to-next-to-leading order. The leading contribution from M1 transition that gives significant contribution in a narrow energy region around the resonance state of B is included. We compare our results with previous halo effective field theory calculations that also included the as an explicit degree of freedom. We disagree with these previous calculations in both the formal expressions and also in the analysis. Bayesian inference of the data gives eV b when combined with the expected theory error.

    Comments:
    21 pages, 11 figures, 4 tables, updated manuscript, results unchanged
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
    arXiv:
    2010.13003 [pdf]
    PRC(2022)·12 citations
  4. 04

    [Submitted on 25 Oct 2020]

    Variational and parquet-diagram calculations for neutron matter. III. S-wave pairing

    E. Krotscheck · J. Wang

    We apply parquet-diagram summation methods for the calculation of the superfluid gap in -wave pairing in neutron matter for realistic nucleon-nucleon interactions such as the Argonne and the Reid potentials. It is shown that diagrammatic contributions that are outside the parquet class play an important role. These are, in variational theories, identified as so-called "commutator contributions". Moreover, using a particle-hole propagator appropriate for a superfluid system results in the suppression of the spin-channel contribution to the induced interaction. Applying these corrections to the pairing interaction, our results agree quite well with Quantum Monte Carlo data.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.13194 [pdf]
    PRC(2021)·7 citations
  5. 05

    [Submitted on 26 Oct 2020]

    Constraining the density dependence of the symmetry energy with nuclear data and astronomical observations in the KIDS framework

    Hana Gil · Young-Min Kim · Panagiota Papakonstantinou · Chang Ho Hyun

    The KIDS framework for the nuclear equation of state (EoS) and energy density functional (EDF) offers the possibility to explore symmetry-energy (SE) parameters such as J (value at saturation density), L (slope), Ksym (curvature) and so on independently of each other and of assumptions about the effective mass. Here we examine the performance of EoSs with different SE parameters in reproducing nuclear properties and astronomical observations in an effort to constrain especially L and Ksym or the droplet-model counterpart Ktau. Assuming a standard EoS for symmetric matter, we explore several points on the hyperplane of (J,L,Ksym or Ktau) values. For each point, the corresponding EDF parameters and a pairing parameter are obtained for applications in spherical even-even nuclei. This is the first application of KIDS EDFs with pairing correlations. The EoSs are tested successively on properties of closed-shell nuclei, along the Sn isotopic chain, and on astronomical observations, in a step-by-step process of elimination and correction. A small regime of best-performing parameters is determined. The results strongly suggest that Ksym is negative and no lower than -200MeV, that Ktau lies between roughly -400 and -300MeV and that L lies between 40 and 65MeV with L<55MeV more likely. Correlations between symmetry-energy parameters are critically discussed. Predictions for the position of the neutron drip line and the neutron skin thickness of selected nuclei are reported. They are only weakly affected by the choice of effective mass values. Parts of the drip line can be sensitive to the SE parameters. The results underscore the role of Ktau and of precise astronomical input. Better constraints are possible with precise fits to nuclear energies and, in the future, more-precise input from astronomy.

    Comments:
    15 pages incl. 7 figures, 4 tables; this version of the preprint (v2) corresponds to the published version (some comments added, a few typos corrected)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.13354 [pdf]
    PRC(2021)·32 citations
  6. 06

    [Submitted on 26 Oct 2020]

    -decay rates of Rh into Pd isotopes in the microscopic IBFM-2

    J. Ferretti · J. Kotila · R. I. Magaña Vsevolodovna · E. Santopinto

    The structure of odd- Rh and Pd isotopes is studied by means of the neutron-proton Interacting Boson-Fermion Model (IBFM-2). quantum number assignment for the Pd ground-states is critically discussed and the predicted energy levels are compared to the existing experimental data. The resulting nuclear wave functions are used to compute the -decay values of the transitions from Rh to Pd in the microscopic IBFM-2 and the results compared with the data.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.13487 [pdf]
    PRC(2020)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE