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Nuclear Theory·nucl-th

Monday·August 3, 2015

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    [Submitted on 30 Jul 2015]

    Range corrections in Proton Halo Nuclei

    Emil Ryberg · Christian Forssén · H.-W. Hammer · Lucas Platter

    We analyze the effects of finite-range corrections in halo effective field theory for S-wave proton halo nuclei. We calculate the charge radius to next-to-leading order and the astrophysical S-factor for low-energy proton capture to fifth order in the low-energy expansion. As an application, we confront our results with experimental data for the S-factor for proton capture on Oxygen-16 into the excited state of Fluorine-17. Our low-energy theory is characterized by a systematic low-energy expansion, which can be used to quantify an energy-dependent model error to be utilized in data fitting. Finally, we show that the existence of proton halos is suppressed by the need for two fine tunings in the underlying theory.

    Comments:
    30pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.08675 [pdf]
    Annals Phys.(2016)·24 citations
  2. 02

    [Submitted on 30 Jul 2015]

    Frustrated fragmentation and re-aggregation in nuclei: a non-equilibrium description in spallation

    P. Napolitani🇫🇷 · M. Colonna🇮🇹

    Heavy nuclei bombarded with protons and deuterons in the 1 GeV range have a large probability of undergoing a process of evaporation and fission; less frequently, the prompt emission of few intermediate-mass fragments can also be observed. We employ a recently developed microscopic approach, based on the Boltzmann-Langevin transport equation, to investigate the role of mean-field dynamics and phase-space fluctuations in these reactions. We find that the formation of few IMF's can be confused with asymmetric fission when relying on yield observables, but it can not be assimilated to the statistical decay of a compound nucleus when analysing the dynamics and kinematic observables: it can be described as a fragmentation process initiated by phase-space fluctuations, and successively frustrated by the mean-field resilience. As an extreme situation, which corresponds to non-negligible probability, the number of fragments in the exit channel reduces to two, so that fission-like events are obtained by re-aggregation processes. This interpretation, inspired by nuclear-spallation experiments, can be generalised to heavy-ion collisions from Fermi to relativistic energies, for situations when the system is closely approaching the fragmentation threshold.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.08698 [pdf]
    PRC(2015)·34 citations
  3. 03

    [Submitted on 31 Jul 2015]

    Shear and Bulk Viscosities of Quark Matter from Quark-Meson Fluctuations in the Nambu--Jona-Lasinio model

    Sabyasachi Ghosh🇧🇷 · Thiago C. Peixoto🇧🇷 · Victor Roy🇩🇪 · Fernando E. Serna🇧🇷 · Gastão Krein🇧🇷

    We have calculated the temperature dependence of shear and bulk viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark- and quark- loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses, and quark-meson couplings are obtained in the Nambu--Jona-Lasinio model. We found a non-trivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios and , where is the entropy density (also determined in the Nambu--Jona-Lasinio model in the quasi-particle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for has a minimum very close to the conjectured AdS/CFT lower bound, .

    Comments:
    10 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1507.08798 [pdf]
    PRC(2016)·57 citations
  4. 04

    [Submitted on 31 Jul 2015]

    Hyperons in nuclear matter from SU(3) chiral effective field theory

    S. Petschauer🇩🇪 · J. Haidenbauer🇩🇪 · N. Kaiser🇩🇪 · Ulf-G. Meißner🇩🇪 · W. Weise🇩🇪

    Brueckner theory is used to investigate the properties of hyperons in nuclear matter. The hyperon-nucleon interaction is taken from chiral effective field theory at next-to-leading order with SU(3) symmetric low-energy constants. Furthermore, the underlying nucleon-nucleon interaction is also derived within chiral effective field theory. We present the single-particle potentials of Lambda and Sigma hyperons in symmetric and asymmetric nuclear matter computed with the continuous choice for intermediate spectra. The results are in good agreement with the empirical information. In particular, our calculation gives a repulsive Sigma-nuclear potential and a weak Lambda-nuclear spin-orbit force.

    Comments:
    13 pages, 10 figures, 5 tables; v2: published version, minor changes
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.08808 [pdf]
    EPJA(2016)·88 citations
  5. 05

    [Submitted on 31 Jul 2015]

    Longitudinal vector form factors in weak decays of nuclei

    F. Simkovic🇷🇺 · S. Kovalenko🇨🇱 · M. I. Krivoruchenko🇷🇺

    The longitudinal form factors of the weak vector current of particles with spin and isospin are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.

    Comments:
    6 pages. Talk given at the 10th MEDEX'15 meeting Matrix Elements for the Double-beta-decay Experiments, Prague, June 9-12, 2015
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1507.08823 [pdf]
    AIP Conf.Proc.(2015)·0 citations
  6. 06

    [Submitted on 31 Jul 2015]

    Exact calculations of a quasi-bound state in the system

    N.V. Shevchenko🇨🇿 · J. Haidenbauer🇩🇪

    Dynamically exact calculations of a quasi-bound state in the three-body system are performed using Faddeev-type AGS equations. As input two phenomenological and one chirally motivated potentials are used, which describe the experimental information on the system equally well and produce either a one- or two-pole structure of the resonance. For the interaction separable potentials are employed that are fitted to phase shifts obtained from two theoretical models. The first one is a phenomenological potential based on meson exchange, which is derived by SU(3) symmetry arguments from the Jülich coupled-channels model. The other interaction is a variant of the first one, which is adjusted to the s-wave scattering length recently determined in lattice QCD simulations. The position and width of the quasi-bound state is evaluated in two ways: (i) by a direct pole search in the complex energy plane and (ii) using an "inverse determinant" method, where one needs to calculate the determinant of the AGS system of equations only for real energies. A quasi-bound state is found with binding energy MeV and width MeV, which could correspond to the experimentally observed state.

    Comments:
    18 pages, 2 figures, 2 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.08839 [pdf]
    PRC(2015)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE