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Nuclear Theory·nucl-th

Monday·November 2, 2020

3 papers—2 primary·1 cross-listed

All3Primary2Cross-lists1
  1. 01

    [Submitted on 30 Oct 2020]

    Neutron-pair structure in the continuum spectrum of O

    S. Affranchino · R.M. Id Betan

    The structure of O is currently being investigated on both theoretical and experimental fronts. It is well established that it is unbound and the resonance parameters are fairly well-known. The theoretical analysis may involved two- and three-body interactions, as well as correlations with the continuum spectrum of energy. In order to properly assess the structure of the ground and excited states, it is imperative to include a large single particle representation with the right asymptotic behavior. The purpose of this work is to provide details of the single particle continuum configurations of the ground and excited states. We use a large complex energy single particle basis, formed by resonances and complex energy scattering states, the so called Berggren basis, and a separable interaction, which is convenient to solve in a large model space. Three states were found in the complex energy plane. Changes of the resonant parameters, i.e. energy and width, were analyzed as a function of strength of the residual interaction. It is shown how a subtle difference in the interaction could change the unbound character of O into a Borromean nucleus. Only one of the two excited states can be considered as a candidate for a physical meaningful resonance. The calculated occupation probabilities are in agreement with other theoretical approaches although the calculated half live is three-order of magnitude smaller than the experimental one.

    Comments:
    7 pages, 5 figures, 5 tables, 47 references
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2010.16192 [pdf]
    PRC(2020)·1 citation
  2. 02

    [Submitted on 30 Oct 2020]

    Study of ()IAS and (He,)IAS charge-exchange reactions with the -matrix folding method

    Phan Nhut Huan🇻🇳 · Nguyen Le Anh🇻🇳 · Bui Minh Loc🇻🇳 · Isaac Vidana🇮🇹

    Differential cross sections of () and (He,) charge-exchange reactions leading to the excitation of the isobaric analog state (IAS) of the target nucleus are calculated with the distorted wave Born approximation. The -matrix double-folding method is employed to determine the nucleus-nucleus optical potential within the framework of the Lane model. -matrices are obtained from a Brueckner-Hartree-Fock calculation using the Argonne Av18 nucleon-nucleon potential. Target densities have been taken from Skyrme-Hartree-Fock calculations which predict values for the neutron skin thickness of heavy nuclei compatible with current existing data. Calculations are compared with experimental data of the reactions ()IAS on C at MeV and Ca at MeV and MeV, and (He,)IAS on Ni, Zr and Pb at MeV. Experimental results are well described without the necessity of any rescaling of the strength of the optical potential. A clear improvement in the description of the differential cross sections for the (He,)IAS reactions on Ni and Zr targets is found when the neutron excess density is used to determine the transition densities. Our results show that the density and isospin dependences of the -matrices play a non-negligible role in the description of the experimental data.

    Comments:
    9 pages, 5 figures. Accepted for publication in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2010.16343 [pdf]
    PRC(2021)·7 citations
  3. 03

    [Submitted on 29 Oct 2020] (cross-list from hep-ph)

    Ambiguities in the definition of local spatial densities in light hadrons

    Robert L. Jaffe🇺🇸

    The relationship between the matrix element of a local operator and the Fourier transform of the associated form factor fails for systems such as the nucleon where its intrinsic size is of order its Compton wavelength. Although one can conceive of an intrinsic charge density distribution in the proton, there does not seem to be an unambiguous way to define, compute, or measure it precisely.

    Comments:
    8 pages, 4 figures; further minor edits, citations added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2010.15887 [pdf]
    PRD(2021)·83 citations

Affiliations

first authorsco-authorsvia INSPIRE