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Nuclear Theory·nucl-th

Thursday·May 21, 2020

10 papers—5 primary·5 cross-listed

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  1. 01

    [Submitted on 20 May 2020]

    Isoscalar monopole and quadrupole modes in Mo isotopes: microscopic analysis

    Gianluca Colo' (1,2) · Danilo Gambacurta (3,4) · Wolfgang Kleinig (5) · Jan Kvasil (6) · Valentin O. Nesterenko (5,7,8) · Alessandro Pastore (9) ((1) Dipartimento di Fisica, Universita degli Studi di Milano, Italy, (2) INFN, Sezione di Milano, Italy, (3) Extreme Light Infrastructure - Nuclear Physics (ELI-NP), Magurele, Romania, (4) LNS-INFN, Catania, Italy, (5) Laboratory of Theoretical Physics, JINR, Dubna, Russia, (6) Institute of Particle and Nuclear Physics, Charles University, Praha, Czech Republic, (7) State University "Dubna'', Russia, (8) Moscow Institute of Physics and Technology, Dolgoprudny, Russia, (9) Department of Physics, University of York, UK)

    The recent RCNP data on the Isoscalar Giant Monopole Resonance (ISGMR) and Isoscalar Giant Quadrupole Resonance (ISGQR) in Mo are analyzed within a fully self-consistent Quasiparticle Random Phase Approximation (QRPA) approach with Skyrme interactions, in which pairing correlations and possible axial deformations are taken into account. The Skyrme sets SkM*, SLy6, SVbas and SkP, that explore a diversity of nuclear matter properties, are used. We discuss the connection between the line shape of the monopole strength ISGMR and the deformation-induced coupling between the ISGMR and the branch of the ISGQR. The ISGMR centroid energy is best described by the force SkP, having a low incompressibility = 202 MeV. The ISGQR data are better reproduced by SVbas, that has large isoscalar effective mass = 0.9. The need of describing simultaneously the ISGMR and ISGQR data is stressed, with the requirement of suitable values of and . Possible extensions of the QRPA to deal with soft systems are also envisaged.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2005.09954 [pdf]
    PLB(2020)·19 citations
  2. 02

    [Submitted on 20 May 2020]

    Correlation studies of fission fragment neutron multiplicities

    M. Albertsson · B.G. Carlsson · T. Døssing · P. Möller · J. Randrup · S. Åberg

    We calculate neutron multiplicities from fission fragments with specified mass numbers for events having a specified total fragment kinetic energy. The shape evolution from the initial compound nucleus to the scission configurations is obtained with the Metropolis walk method on the five-dimensional potential-energy landscape, calculated with the macroscopic-microscopic method for the three-quadratic-surface shape family. Shape-dependent microscopic level densities are used to guide the random walk, to partition the intrinsic excitation energy between the two proto-fragments at scission, and to determine the spectrum of the neutrons evaporated from the fragments. The contributions to the total excitation energy of the resulting fragments from statistical excitation and shape distortion at scission is studied. Good agreement is obtained with available experimental data on neutron multiplicities in correlation with fission fragments from U(n,f). At higher neutron energies a superlong fission mode appears which affects the dependence of the observables on the total fragment kinetic energy.

    Comments:
    12 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.09988 [pdf]
    PRC(2021)·24 citations
  3. 03

    [Submitted on 20 May 2020]

    Exact sum rules with approximate ground states

    Calvin W. Johnson · Ken A. Luu · Yi Lu

    Electromagnetic and weak transitions tell us a great deal about the structure of atomic nuclei. Yet modeling transitions can be difficult: it is often easier to compute the ground state, if only as an approximation, than excited states. One alternative is through transition sum rules, in particular the non-energy-weighted and energy-weighted sum rules, which can be computed as expectation values of operators. We investigate by computing sum rules for a variety of nuclei, comparing the numerically exact full configuration-interaction shell model, as a reference, to Hartree-Fock, projected Hartree-Fock, and the nucleon pair approximation. These approximations yield reasonable agreement, which we explain by prior work on the systematics of transition moments.

    Comments:
    15 pages, 5 figures, 1 table; revised version to match published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.10143 [pdf]
    J.Phys.G(2020)·6 citations
  4. 04

    [Submitted on 20 May 2020]

    Future of Nuclear Fission Theory

    Michael Bender🇫🇷 · Remi Bernard🇦🇺 · George Bertsch🇺🇸 · Satoshi Chiba🇯🇵 · Jacek Dobaczewski🇬🇧 · Noel Dubray🇫🇷 · Samuel Giuliani🇺🇸 · Kouichi Hagino🇯🇵 · Denis Lacroix🇫🇷 · Zhipan Li🇨🇳 · Piotr Magierski🇵🇱 · Joachim Maruhn🇩🇪 and 21 other authors

    There has been much recent interest in nuclear fission, due in part to a new appreciation of its relevance to astrophysics, stability of superheavy elements, and fundamental theory of neutrino interactions. At the same time, there have been important developments on a conceptual and computational level for the theory. The promising new theoretical avenues were the subject of a workshop held at the University of York in October 2019; this report summarises its findings and recommendations.

    Comments:
    86 LaTeX pages, 3 figures, 331 references, version published as Topical Review in Journal of Physics G
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.10216 [pdf]
    J.Phys.G(2020)·163 citations
  5. 05

    [Submitted on 20 May 2020]

    Chirally improved quark Pauli blocking in nuclear matter and applications to quark deconfinement in neutron stars

    David Blaschke🇵🇱 · Hovik Grigorian🇷🇺 · Gerd Röpke🇷🇺

    The relativistic mean field (RMF) model of the nuclear matter equation of state has been modified by including the effect of Pauli-blocking owing to quark exchange between the baryons. Different schemes of a chiral enhancement of the quark Pauli blocking have been suggested according to the adopted density dependence of the dynamical quark mass. The resulting equations of state for the pressure are compared to the RMF model DD2 with excluded volume correction. On the basis of this comparison a density-dependent nucleon volume is extracted which parametrises the quark Pauli blocking effect in the respective scheme of chiral enhancement. The dependence on the isospin asymmetry is investigated and the corresponding density dependent nuclear symmetry energy is obtained in fair accordance with phenomenological constraints. The deconfinement phase transition is obtained by a Maxwell construction with a quark matter phase described within a higher order NJL model. Solutions for rotating and nonrotating (hybrid) compact star sequences are obtained which show the effect of high-mass twin compact star solutions for the rotating case.

    Comments:
    20 pages, 12 figures, 3 tables, text revised and extended, figures updated, references added, accepted for publication in Particles (2020)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2005.10218 [pdf]
    Particles(2020)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE