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Nuclear Theory·nucl-th

Monday·July 25, 2016

4 papers—3 primary·1 cross-listed

All4Primary3Cross-lists1
  1. 01

    [Submitted on 22 Jul 2016]

    Spin-orbit interaction in relativistic nuclear structure models

    J.-P. Ebran🇫🇷 · A. Mutschler🇫🇷 · E. Khan🇫🇷 · D. Vretenar🇭🇷

    Relativistic self-consistent mean-field (SCMF) models naturally account for the coupling of the nucleon spin to its orbital motion, whereas non-relativistic SCMF methods necessitate a phenomenological ansatz for the effective spin-orbit potential. Recent experimental studies aim to explore the isospin properties of the effective spin-orbit interaction in nuclei. SCMF models are very useful in the interpretation of the corresponding data, however standard relativistic mean-field and non-relativistic Hartree-Fock models use effective spin-orbit potentials with different isovector properties, mainly because exchange contributions are not treated explicitly in the former. The impact of exchange terms on the effective spin-orbit potential in relativistic mean-field models is analysed, and it is shown that it leads to an isovector structure similar to the one used in standard non-relativistic Hartree-Fock. Data on the isospin dependence of spin-orbit splittings in spherical nuclei could be used to constrain the isovector-scalar channel of relativistic mean-field models. The reproduction of the empirical kink in the isotope shifts of even Pb nuclei by relativistic effective interactions points to the occurrence of pseudospin symmetry in the single-neutron spectra in these nuclei.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1607.06567 [pdf]
    PRC(2016)·20 citations
  2. 02

    [Submitted on 22 Jul 2016]

    Properties of isocalar-pair condensates

    P. Van Isacker🇫🇷 · A.O. Macchiavelli🇺🇸 · P. Fallon🇺🇸 · S. Zerguine🇩🇿

    It is pointed out that the ground state of n neutrons and n protons in a single-j shell, interacting through an isoscalar (T=0) pairing force, is not paired, J=0, but rather spin-aligned, J=n. This observation is explained in the context of a model of isoscalar P (J=1) pairs, which is mapped onto a system of p bosons, leading to an approximate analytic solution of the isoscalar-pairing limit in jj coupling.

    Comments:
    7 pages, 3 figures, 1 table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1607.06593 [pdf]
    PRC(2016)·8 citations
  3. 03

    [Submitted on 22 Jul 2016]

    From the Coulomb breakup of halo nuclei to neutron radiative capture

    Pierre Capel · Yvan Nollet

    Coulomb breakup is used to infer radiative-capture cross sections at astrophysical energies. We test theoretically the accuracy of this indirect technique in the particular case of 15C, for which both the Coulomb breakup to ^{14}C+n and the radiative capture 14C(n,{\gamma})15C have been measured. We analyse the dependance of Coulomb-breakup calculations on the projectile description in both its initial bound state and its continuum. Our calculations depend not only on the Asymptotic Normalisation Coefficient (ANC) of the 15C ground state, but also on the 14C-n continuum. This questions the method proposed by Summers and Nunes [Phys. Rev. C 78, 011601 (2008), ibid. 78, 069908 (2008)], which assumes that an ANC can be directly extracted from the comparison of calculations to breakup data. Fortunately, the sensitivity to the continuum description can be absorbed in a normalisation constant obtained by a simple {\chi}2 fit of our calculations to the measurements. By restricting this fit to low 14C-n energy in the continuum, we can achieve a better agreement between the radiative-capture cross sections inferred from the Coulomb-breakup method and the exact ones. This result revives the Coulomb-breakup technique to infer neutron radiative-capture capture to loosely-bound states, which would be very useful for r- and s-process modelling in explosive stellar environments.

    Comments:
    8 pages, 7 figures, contribution to the proceedings of the 54th International Winter Meeting on Nuclear Physics (25-29 January 2016, Bormio, Italy)
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
    arXiv:
    1607.06791 [pdf]
    PoS(2016)·0 citations
  4. 04

    [Submitted on 21 Jul 2016] (cross-list from hep-lat)

    Mirage in Temporal Correlation functions for Baryon-Baryon Interactions in Lattice QCD

    Takumi Iritani🇺🇸 · Takumi Doi🇯🇵 · Sinya Aoki🇯🇵 · Shinya Gongyo🇫🇷 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Keiko Murano🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵

    Single state saturation of the temporal correlation function is a key condition to extract physical observables such as energies and matrix elements of hadrons from lattice QCD simulations. A method commonly employed to check the saturation is to seek for a plateau of the observables for large Euclidean time. Identifying the plateau in the cases having nearby states, however, is non-trivial and one may even be misled by a fake plateau. Such a situation takes place typically for the system with two or more baryons. In this study, we demonstrate explicitly the danger from a possible fake plateau in the temporal correlation functions mainly for two baryons ( and ), and three and four baryons ( and as well, employing (2+1)-flavor lattice QCD at GeV on four lattice volumes with 2.9, 3.6, 4.3 and 5.8 fm. Caution is given for drawing conclusion on the bound , and systems only based on the temporal correlation functions.

    Comments:
    32 pages, 13 figures, minor corrections, published version, typos corrected
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1607.06371 [pdf]
    JHEP(2016)·85 citations

Affiliations

first authorsco-authorsvia INSPIRE