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Nuclear Theory·nucl-th

Wednesday·October 18, 2017

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 01

    [Submitted on 17 Oct 2017]

    Gamow-Teller response in the configuration space of DFT-rooted no-core configuration-interaction model

    Maciej Konieczka · Markus Kortelainen · Wojciech Satuła

    The atomic nucleus is a unique laboratory to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics. We have performed a seminal calculation of the GT response by using the no-core-configuration-interaction approach rooted on multi-reference density functional theory (DFT-NCCI). The model treats properly isospin and rotational symmetries and can be applied to calculate both the nuclear spectra and transition rates in atomic nuclei, irrespectively of their mass and particle-number parity. The method is applied to compute the GT strength distribution in selected nuclei including the -shell Li and Be nuclei and the -shell well-deformed nucleus Mg. In order to demonstrate a flexibility of the approach we present also a calculation of the superallowed GT beta decay in doubly-magic spherical Sn and the low-spin spectrum in In. It is demonstrated that the DFT-NCCI model is capable to capture the GT response satisfactorily well by using relatively small configuration space exhausting simultaneously the GT sum rule. The model, due to its flexibility and broad range of applicability, may either serve as a complement or even as an alternative to other theoretical approaches including the conventional nuclear shell model.

    Comments:
    13 pages, 15 figures, submitted to Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1710.06172 [pdf]
    PRC(2018)·12 citations
  2. 02

    [Submitted on 17 Oct 2017]

    Study of the Q.Q Interaction- Single Particle Behavior to Elliott's Rotations

    Arun Kingan · Xiaofei Yu · Larry Zamick

    We perform shell model calculations using a quadrupole-quadrupole interaction (Q.Q).We show results in single j shell spaces and the full S-D shell . We show that one gets useful results with Q.Q in both spaces.. We emphasize the importance of the choice of single particle energies in order to obtain the results of Elliott using a Q.Q interaction without the momentum terms. We show a J(J+1) spectrum for a ground state band but with B(E2)'s different from the rotational model. We also show excited J(J-1), J((J-1) and J(J+3) spectra.We find spectra starting with J=0 which have both even J and odd J members.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
    arXiv:
    1710.06218 [pdf]
    IJMPE(2018)·2 citations
  3. 03

    [Submitted on 17 Oct 2017]

    Thermal dileptons as QCD matter probes at SIS

    Florian Seck🇩🇪 · Tetyana Galatyuk🇩🇪 · Ralf Rapp🇺🇸 · Joachim Stroth🇩🇪

    Electromagnetic radiation is emitted during the whole course of a heavy-ion collision and can escape from the collision zone without further interactions. This makes it an ideal tool to study the properties of hot and dense QCD matter. To model the space-time evolution of the collision at SIS energies a coarse-graining approach is used to convert transport simulations into meaningful temperatures and densities. These parameters serve as input for the determination of the pertinent radiation of thermal dileptons based on an in-medium spectral function that describes available spectra at ultrarelativistic collision energies. The resulting excitation function of the thermal excess radiation provides a baseline for future measurements by the HADES and CBM experiments at GSI/FAIR, and experiments proposed at NICA and J-PARC.

    Comments:
    5 pages, 5 figures, contribution to FAIRness 2017 - FAIR next generation scientists - 5th Edition Workshop (May 28, 2017 to June 3, 2017 in Sitges, Spain)
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1710.06256 [pdf]
    J.Phys.Conf.Ser.(2018)·4 citations
  4. 04

    [Submitted on 17 Oct 2017]

    Isospin-forbidden electric-dipole capture and the Li reaction

    Daniel Baye · E.M. Tursunov

    At the long-wavelength approximation, transitions are forbidden between isospin-zero states. Hence radiative capture is strongly hindered in reactions involving nuclei but the astrophysical factor may remain comparable to, or larger than, the one. Theoretical expressions of the isoscalar and isovector contributions to capture are analyzed in microscopic and three-body approaches in the context of the Li reaction. The lowest non-vanishing terms of the operators are derived and the dominant contributions to matrix elements are discussed. The astrophysical factor computed with some of these contributions in a three-body model is in agreement with the recent low-energy experimental data of the LUNA collaboration. This confirms that a correct treatment of the isovector transitions involving small isospin-one admixtures in the wave functions should be able to provide an explanation of the data without adjustable parameter. The exact-masses prescription which is often used to avoid the disappearance of the matrix element in potential models is not founded at the microscopic level and should not be used for such reactions. The importance of capture components from an initial scattering wave is also discussed.

    Comments:
    24 pages, 1 table, 2 figures, Figures and text updated
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    1710.06352 [pdf]
    J.Phys.G(2018)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE