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Nuclear Theory·nucl-th

Tuesday·May 21, 2019

11 papers—5 primary·6 cross-listed

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  1. 01

    [Submitted on 17 May 2019]

    On the convergence of nuclear effective field theory with perturbative pions

    David B. Kaplan🇺🇸

    The classic paper by Fleming, Mehen and Stewart cast doubts on the convergence of spin-triplet nucleon-nucleon partial wave scattering amplitudes when following the proposal of Kaplan, Savage and Wise to construct nuclear effective field theory around the unitary fermion limit with perturbative pion exchange. FMS identified the subclass of iterated one-pion exchange potential graphs as the cause of this poor convergence, which they showed persisted in the chiral limit. Theoretical tools are developed here to compute these Feynman graphs analytically to high order in all angular momentum channels simultaneously, examining the amplitudes computed to seven loops in the channels, and three loops in the coupled channels. One finds that there is nothing pathological about the perturbative expansion of a potential in general, and that the expansion converges satisfactorily in all partial waves except those with the lowest angular momentum, particularly the and the coupled channels. The results corroborate work by Birse, which suggests possible avenues to explore for improving the range of validity of the EFT expansion.

    Comments:
    This revision aligns with the published version and includes a discussion of related work from atomic physics which has allows for a nonperturbative estimate of the radius of convergence of the KSW expansion in each partial wave, which is shown to agree well with the perturbative results computed here. 32 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1905.07485 [pdf]
    PRC(2020)·41 citations
  2. 02

    [Submitted on 19 May 2019]

    Effects of the Coulomb interaction on parameters of resonance states in mirror three-cluster nuclei

    A.D. Duisenbay · N. Kalzhigitov · K. Katō · V. O. Kurmangaliyeva · N. Takibayev · V. S. Vasilevsky

    We investigate how the Coulomb interaction affects the energy and width of resonance states in mirror nuclei. We employ a three-cluster microscopic model to determine position of resonance states in two- and three-body continua. Two parameters are introduced to quantify effects of the Coulomb interactions. As the energy and width of the corresponding resonance states of mirror nuclei are displayed on an - plane, these parameters determine a rotation and a dilatation. With the help of these parameters we found resonance states with strong, small and medium effects of the Coulomb interaction. We also found two different scenarios of the motion of resonance states due to the Coulomb interaction. The first standard (major) scenario represent resonance states with the larger energy and larger width than their counterparts have. The second rear scenario includes resonance states with the larger energy but smaller width.

    Comments:
    55 pages, 22 figures, two new paragraphs are added and typos are corrected, submitted to Nucl. Phys . A
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1905.07711 [pdf]
    NPA(2020)·7 citations
  3. 03

    [Submitted on 20 May 2019]

    Effects of pairing, continuum, and deformation on particles in the classically forbidden regions for Mg isotopes

    Kaiyuan Zhang · Dongyang Wang · Shuangquan Zhang

    Particles in the classically forbidden regions are studied based on the deformed relativistic Hartree-Bogoliubov theory in continuum with PC-PK1 for magnesium isotopes. By analyzing the neutron and proton radii, it is found that the largest deviations from the empirical values appear at the predicted neutron halo nuclei Mg and Mg. Consistently, notable increases at Mg and Mg are found in the total number of neutrons in the classically forbidden regions that includes the number of neutrons in continuum. It is shown that the deformation effect, in general, increases the number of particles in the classically forbidden regions below the continuum threshold. The most deeply bound single-particle states play the dominant roles in the increase caused by deformation.

    Comments:
    18 pages, 6 figures. Accepted for publication in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1905.07930 [pdf]
    PRC(2019)·62 citations
  4. 04

    [Submitted on 20 May 2019]

    Ca and Ca with the (Many- and Few-body) Unified Method

    E. Garrido · A.S. Jensen

    A new method unifying many and few-body aspects of nuclear structure has recently been introduced \cite{hov18}. This method combines the many-body description of a core and the few-body structure of this core surrounded by two valence nucleons. For this reason this method is expected to work specially well when applied to nuclei close to the driplines, where the few-body halo structure with one or more nucleons outside the core is established. In this work we apply the new method to nuclei close to the valley of stability, with Ca and Ca as illustrations. We compare the results from uncorrelated mean-field calculations with the ones obtained with the unified method allowing arbitrary correlations in the valence space. We find that the unified method provides results rather similar, although distinguishable, to the Hartree-Fock calculations. The correlations are much less pronounced than at the driplines, which initially were targets for the unified method. The halo structure is not artificially maintained, but the correlations are here demonstrated to be applicable to well-bound nuclei. Excited states built on valence degrees of freedom are calculated for the same nuclei.

    Comments:
    To be published in Few-body Systems
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1905.07971 [pdf]
    Few Body Syst.(2019)·1 citation
  5. 05

    [Submitted on 20 May 2019]

    Microscopic three-cluster study of light exotic nuclei

    P. Descouvemont

    I develop a microscopic three-cluster model for exotic light nuclei. I use the hyperspherical formalism, associated with the Generator Coordinate Method. This model is well adapted to halo nuclei, since the long-range part of the radial wave functions is accurately reproduced. The core wave functions are described in the shell model, including excited states. This technique provides large bases, expressed in terms of projected Slater determinants. Matrix elements involve seven-dimension integrals, and therefore require long calculation times. I apply the model to 11Li, 14Be, 15B, and 17N described by two neutrons surrounding a 9Li, 12Be, 13B and 15N core, respectively. The 17Ne (as 15O+p+p) and 15Ne (as 13O+p+p) mirror nuclei are briefly discussed. I present the spectra and some spectroscopic properties, such as r.m.s. radii or E2 transition probabilities. I also analyze the importance of core excitations.

    Comments:
    Accepted for publication in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1905.07979 [pdf]
    PRC(2019)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE