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Nuclear Theory·nucl-th

Thursday·August 3, 2017

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    Truncation scheme of time-dependent density-matrix approach II

    Mitsuru Tohyama🇯🇵 · Peter Schuck🇫🇷

    A truncation scheme of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for reduced density matrices, where a three-body density matrix is approximated by two-body density matrices, is improved to take into account a normalization effect. The truncation scheme is tested for the Lipkin model. It is shown that the obtained results are in good agreement with the exact solutions.

    nucl-thEPJA(2017)·8 citations
  2. 02

    Radial Overlap Correction to Superallowed -decay revisited

    Latsamy Xayavong🇫🇷 · Nadezda Smirnova🇫🇷

    Within the nuclear shell model, we investigate the correction to the Fermi matrix element due to a mismatch between proton and neutron single-particle radial wave functions. Eight superallowed decays in the -shell, comprised of Mg, Al, Si, S, Cl, Ar, K and Ca are re-examined. The radial wave functions are obtained from a spherical Woods-Saxon potential whose parametrizations are optimized in a consistent adjustment of the depth and the length parameter to relevant experimental observables, such as nucleon separation energies and charge radii, respectively. The chosen fit strategy eliminates the strong dependence of the radial mismatch correction to a specific parametrization, except for calculations with an additional surface-peaked term. As an improvement, our model proposes a new way to calculate the charge radii, based on a parentage expansion which accounts for correlations beyond the extreme independent-particle model. Apart from the calculations with a surface-peak term and the cases where we used a different model space, the new sets of are in general agreement with the earlier result of Towner and Hardy [1]. Small differences of the corrected average value are observed.

    nucl-thPRC(2018)·35 citations
  3. 03

    The Casimir-Polder interaction between two neutrons and possible relevance to tetraneutron states

    M. S. Hussein🇧🇷 · J. Babb🇺🇸 · R. Higa🇧🇷

    We present a summary of our recent publication concerning the derivation of the extended Casimir-Polder dispersive interaction between two neutrons. Dynamical polarizations of the neutrons, recently derived within Chiral Effective Theory are used for the purpose. An account of the higher frequency/energy behavior of these entities related to the opening of one-pion production channel and the excitation of the resonance are taken into consideration in our derivation of the CP interaction. The neutron-neutron system in free space is treated in details so are the neutron-wall and the wall-neutron-wall systems. The case of tetraneutron (a 4 neutron system) in a resonant state is then briefly considered. The 4n CP interaction is evaluated to assess its potential relevance to the ongoing debate concerning the nature of the tetraneutron.

    nucl-thhep-phnucl-exActa Phys.Polon.B(2017)·2 citations
  4. 04

    Intrinsic properties of high-spin band structures in triaxial nuclei

    S. Jehangir · G.H. Bhat · J.A. Sheikh · R. Palit · P.A. Ganai

    The band structures of Ge, Ce and Nd are investigated using the triaxial projected shell model (TPSM) approach. These nuclei depict forking of the ground-state band into several s-bands and in some cases, both the lowest two observed s-bands depict neutron or proton character. It was discussed in our earlier work that this anamoluos behaviour can be explained by considering -bands based on two-quasiparticle configurations. As the parent band and the -band built on it have the same intrinsic structure, g-factors of the two bands are expected to be similar. In the present work, we have undertaken a detailed investigation of g-factors for the excited band structures of the studied nuclei and the available data for a few high-spin states are shown to be in fair agreement with the predicted values.

    nucl-thnucl-exNPA(2017)·18 citations
  5. 05

    Bulk Viscosity of Quark-Gluon Plasma in Strong Magnetic Fields

    Koichi Hattori🇨🇳 · Xu-Guang Huang🇨🇳 · Dirk H. Rischke🇩🇪 · Daisuke Satow🇩🇪

    We investigate the viscosities of the quark-gluon plasma in strong magnetic fields within the leading-log and lowest Landau level (LLL) approximations. We first show that the bulk viscosity in the direction parallel to the magnetic field is the only component that has a contribution from the quarks occupying the LLL. We then compute the bulk viscosity from the Kubo formula and find an intriguing quark-mass dependence as a consequence of a competition between the suppression of the bulk viscosity by conformal symmetry and an enhancement of the mean-free path by chirality conservation, which governs the behavior in the massless limit. The quark contribution to the viscosity along the magnetic field becomes larger than the one in the absence of a magnetic field. We also briefly estimate the other transport coefficients by considering the contribution of gluons. We show that the shear viscosities are suppressed compared to their values in the absence of a magnetic field.

    ↳ hep-phnucl-thPRD(2017)·89 citations
  6. 06

    High-precision -value measurement of the superallowed emitter Mg and an evaluation of the isobaric triplet

    M.P. Reiter🇨🇦 · K.G. Leach🇺🇸 · O. M. Drozdowski🇨🇦 · S.R. Stroberg🇨🇦 · J.D. Holt🇨🇦 · C. Andreoiu🇨🇦 · C. Babcock🇨🇦 · B. Barquest🇨🇦 · M. Brodeur🇺🇸 · A. Finlay🇨🇦 · M. Foster🇬🇧 · A.T. Gallant🇨🇦 and 13 other authors

    A direct -value measurement of the superallowed emitter Mg was performed using TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The direct ground-state to ground-state atomic mass difference between Mg and Na was determined to be ~keV, representing the most precise single measurement of this quantity to date. In a continued push towards calculating superallowed isospin-symmetry-breaking (ISB) corrections from first principles, ab-initio shell-model calculations of the IMME are also presented for the first time using the valence-space in-medium similarity renormalization group formalism. With particular starting two- and three-nucleon forces, this approach demonstrates a level of agreement with the experimental data that suggests reliable ab-initio calculations of superallowed ISB corrections are now possible.

    ↳ nucl-exnucl-thPRC(2017)·13 citations
  7. 07

    Lambda beta-decay in-medium

    P.A.M. Guichon🇫🇷 · A.W. Thomas🇦🇺

    Under the working hypothesis that the structure of a bound hadron is modified by its interactions with other hadrons, one may expect to see changes in carefully chosen observables. In the light of a recent proposal to measure the axial charge in the strangeness changing beta-decay of a bound Lambda hyperon, we examine the size of the change expected within the quark-meson coupling model. It is predicted to be significant.

    ↳ hep-phnucl-thPLB(2017)·6 citations

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