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Nuclear Theory·nucl-th

Thursday·September 14, 2017

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 01

    [Submitted on 12 Sept 2017]

    RAINIER: A Simulation Tool for Distributions of Excited Nuclear States and Cascade Fluctuations

    L. E. Kirsch · L. A. Bernstein

    A new code has been developed named RAINIER that simulates the -ray decay of discrete and quasi-continuum nuclear levels for a user-specified range of energy, angular momentum, and parity including a realistic treatment of level spacing and transition width fluctuations. A similar program, DICEBOX, uses the Monte Carlo method to simulate level and width fluctuations but is restricted to -ray decay from no more than two initial states such as de-excitation following thermal neutron capture. On the other hand, modern reaction codes such as TALYS and EMPIRE populate a wide range of states in the residual nucleus prior to -ray decay, but do not go beyond the use of deterministic functions and therefore neglect cascade fluctuations. This combination of capabilities allows RAINIER to be used to determine quasi-continuum properties through comparison with experimental data. Several examples are given that demonstrate how cascade fluctuations influence experimental high-resolution -ray spectra from reactions that populate a wide range of initial states.

    Comments:
    14 pages, 13 figures, Nuclear Instrumentation and Methods A, 2017
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1709.04006 [pdf]
    Nucl.Instrum.Meth.A(2018)·22 citations
  2. 02

    [Submitted on 12 Sept 2017]

    Projection of angular momentum via linear algebra

    Calvin W. Johnson · Kevin D. O'Mara

    Projection of many-body states with good angular momentum from an initial state is usually accomplished by a three-dimensional integral. We show how projection can instead be done by solving a straightforward system of linear equations. We demonstrate the method and give sample applications to Cr and Fe in the shell. This new projection scheme, which is competitive against the standard numerical quadrature, should also be applicable to other quantum numbers such as isospin and particle number.

    Comments:
    14 pages, 2 figures, 1 table
    Subjects:
    Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
    arXiv:
    1709.04028 [pdf]
    PRC(2017)·23 citations
  3. 03

    [Submitted on 13 Sept 2017]

    Algebraic diagrammatic construction formalism with three-body interactions

    Francesco Raimondi · Carlo Barbieri

    Self-consistent Green's function theory has recently been extended to the basic formalism needed to account for three-body interactions [A. Carbone, A. Cipollone, C. Barbieri, A. Rios, and A. Polls, (Phys. Rev. C 88, 054326 (2013))]. The contribution of three-nucleon forces has so far been included in ab initio calculations on nuclear matter and finite nuclei only as averaged two-nucleon forces. We derive the working equations for all possible two- and three-nucleon terms that enter the expansion of the self-energy up to the third order, thus including the interaction-irreducible (i.e., not averaged) diagrams with three-nucleon forces that have been previously neglected. We employ the algebraic diagrammatic construction up to the third order as an organization scheme for generating a non perturbative self-energy, in which ring (particle-hole) and ladder (particle-particle) diagrams are resummed to all orders. We derive expressions of the static and dynamic self-energy up to the third order, by taking into account the set of diagrams required when either the skeleton or nonskeleton expansions of the single-particle propagator are assumed. A hierarchy of importance among different diagrams is revealed, and a particular emphasis is given to a third-order diagram (see Fig. 2c) that is expected to play a significant role among those featuring an interaction-irreducible three-nucleon force. A consistent formalism to resum at infinite order correlations induced by three-nucleon forces in the self-consistent Green's function theory is now available and ready to be implemented in the many-body solvers.

    Comments:
    35 pages, 15 figures (significant changes to the text and corrected typos in the text and equations)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1709.04330 [pdf]
    PRC(2018)·37 citations
  4. 04

    [Submitted on 13 Sept 2017]

    Towards microscopic studies of survival probabilities of compound superheavy nuclei

    Yi Zhu · Junchen Pei

    The microscopic approach of fission rates and neutron emission rates in compound nuclei have been applied to No and Cn. The microscopic framework is based on the finite-temperature Skyrme-Hartree-Fock+BCS calculations, in which the fission barriers and mass parameters are self-consistently temperature dependent. The fission rates from low to high temperatures can be obtained based on the imaginary free energy method. The neutron emission rates are obtained with neutron gases at surfaces. Finally the survival probabilities of superheavy nuclei can be calculated microscopically. The microscopic approach has been compared with the widely used statistical models. Generally, there are still large uncertainties in descriptions of fission rates.

    Comments:
    9 pages,7 figures, accepted for Physica Scripta Special Issue
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1709.04350 [pdf]
    Phys.Scripta(2017)·4 citations
  5. 05

    [Submitted on 12 Sept 2017]

    Distillation of scalar exchange by coherent hypernucleus production in antiproton-nucleus collisions

    A.B. Larionov🇩🇪 · H. Lenske🇩🇪

    The total and angular differential cross sections of the coherent process are evaluated at the beam momenta GeV/c within the meson exchange model with bound proton and -hyperon wave functions. It is shown that the shape of the beam momentum dependence of the hypernucleus production cross sections with various discrete states is strongly sensitive to the presence of the scalar -meson exchange in the amplitude. This can be used as a clean test of the exchange by scalar correlation in coherent reactions.

    Comments:
    12 pages, 6 figures, accepted in Phys. Lett. B. arXiv admin note: substantial text overlap with arXiv:1703.02073
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1709.04370 [pdf]
    PLB(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE