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Nuclear Theory·nucl-th

Monday·April 6, 2015

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 2 Apr 2015]

    Kaon and pion parton distribution amplitudes to twist-three

    Chao Shi🇨🇳 · Chen Chen🇨🇳 · Lei Chang🇦🇺 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪 · Hong-Shi Zong🇨🇳

    We compute all kaon and pion parton distribution amplitudes (PDAs) to twist-three and find that only the pseudotensor PDA can reasonably be approximated by its conformal limit expression. At terrestrially accessible energy scales, the twist-two and pseudoscalar twist-three PDAs differ significantly from those functions commonly associated with their forms in QCD's conformal limit. In all amplitudes studied, SU(3) flavour-symmetry breaking is typically a 13% effect. This scale is determined by nonperturbative dynamics; namely, the current-quark-mass dependence of dynamical chiral symmetry breaking. The heavier-quark is favoured by this distortion, for example, support is shifted to the s-quark in the negative kaon. It appears, therefore, that at energy scales accessible with existing and foreseeable facilities, one may obtain reliable expectations for experimental outcomes by using these "strongly dressed" PDAs in formulae for hard exclusive processes. Following this procedure, any discrepancies between experiment and theory will be significantly smaller than those produced by using the conformal-limit PDAs. Moreover, the magnitude of any disagreement will either be a better estimate of higher-order, higher-twist effects or provide more realistic constraints on the Standard Model.

    Comments:
    14 pages, 4 figures, 2 tables. arXiv admin note: text overlap with arXiv:1406.3353
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1504.00689 [pdf]
    PRD(2015)·82 citations
  2. 02

    [Submitted on 3 Apr 2015]

    Systematics of capture and fusion dynamics in heavy-ion collisions

    Bing Wang · Kai Wen · Wei-Juan Zhao · En-Guang Zhao · Shan-Gui Zhou

    We perform a systematic study of capture excitation functions by using an empirical coupled-channel model. In this model, a barrier distribution is used to take effectively into account the effects of couplings between the relative motion and intrinsic degrees of freedom. The shape of the barrier distribution is of an asymmetric Gaussian form. The effect of neutron transfer channels is also included in the barrier distribution. Based on the interaction potential between the projectile and the target, empirical formulas are proposed to determine the parameters of the barrier distribution. Theoretical estimates for barrier distributions and calculated capture cross sections together with experimental cross sections of 220 reaction systems with are tabulated. The results show that our empirical formulas work quite well in the energy region around the Coulomb barrier. This model can provide prediction of capture cross sections for the synthesis of superheavy nuclei as well as valuable information on capture and fusion dynamics.

    Comments:
    120 pages, 32 figures, 3 tables, accepted for publication in Atomic Data and Nuclear Data Tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1504.00756 [pdf]
    Atom.Data Nucl.Data Tabl.(2017)·65 citations
  3. 03

    [Submitted on 3 Apr 2015]

    The competition between alpha decay and spontaneous fission in odd-even and odd-odd nuclei in the range 99 \leg Z \leg 129

    K. P. Santhosh · B. Priyanka

    The predictions on the mode of decay of the odd-even and odd-odd isotopes of heavy and superheavy nuclei with Z = 99-129, in the range 228 \leg A \leg 336, have been done within the Coulomb and proximity potential model for deformed nuclei (CPPMDN). A comparison of our calculated alpha half lives with the values computed using other theoretical models shows good agreement with each other. An extensive study on the spontaneous fission half lives of all the isotopes under study has been performed to identify the long-lived isotopes in the mass region. The study reveals that the alpha decay half lives and the mode of decay of the isotopes with Z = 109, 111, 113, 115 and 117, evaluated using our formalisms, agrees well with the experimental observations. As our study on the odd-even and odd-odd isotopes of Z = 99-129 predicts that, the isotopes 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127 and 129 survive fission and have alpha decay channel as the prominent mode of decay, these nuclei could possibly be synthesized in the laboratory and this could be of great interest to the experimentalists. The behaviour of these nuclei against the proton decay has also been studied to identify the probable proton emitters in this region of nuclei.

    Comments:
    47 pages, 14 figures, to appear in Nuclear Physics A (2015)
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1504.00872 [pdf]
    NPA(2015)·26 citations
  4. 04

    [Submitted on 3 Apr 2015]

    Scalar Pseudo-Nambu-Goldstone Boson in Nuclei and Dense Nuclear Matter

    Hyun Kyu Lee🇰🇷 · Won-Gi Paeng🇰🇷 · Mannque Rho🇫🇷

    The notion that the scalar listed as in the particle data booklet is a pseudo-Nambu-Goldstone (NG) boson of spontaneously broken scale symmetry, explicitly broken by a small departure from an infrared fixed point, is explored in nuclear dynamics. That notion which puts the scalar -- that we shall identify as a "dilaton" -- on the same footing as the pseudo-scalar pseudo-NG bosons, i.e., octet , while providing a simple explanation for the rule for kaon decay, generalizes the standard chiral perturbation theory (SPT) to "scale chiral perturbation theory," denoted PT, with {\it one infrared mass scale for both symmetries}, with the figuring as a chiral singlet NG mode in non-strange sector. Applied to nuclear dynamics, it is seen to provide possible answers to various hitherto unclarified nuclear phenomena such as the success of one-boson-exchange potentials (OBEP), the large cancellation of strongly attractive scalar potential by strongly repulsive vector potential in relativistic mean field theory of nuclear systems and in-medium QCD sum rules, the interplay of the dilaton and the vector meson in dense skyrmion matter, the BPS skyrmion structure of nuclei accounting for small binding energies of medium-heavy nuclei, and the suppression of hyperon degrees of freedom in compact-star matter.

    Comments:
    14 pages, 1 figure
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1504.00908 [pdf]
    PRD(2015)·24 citations
  5. 05

    [Submitted on 3 Apr 2015]

    Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    P. M. Goddard · P. D. Stevenson · A. Rios

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the barrier explore large amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation. Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

    Comments:
    Amended version, accepted for publication in Phys. Rev. C. 22 pages, 20 figures, 7 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1504.00919 [pdf]
    PRC(2015)·111 citations

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first authorsco-authorsvia INSPIRE