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Nuclear Theory·nucl-th

Wednesday·October 16, 2019

7 papers—5 primary·2 cross-listed

All7Primary5Cross-lists2
  1. 01

    [Submitted on 15 Oct 2019]

    Collectivity of the electromagnetic transitions in near-threshold resonances

    M. Płoszajczak🇫🇷 · J. Okołowicz🇵🇱

    Mixing of the shell model (SM) eigenstates due to the coupling via the common decay channel leads in many cases to the formation of a collective eigenstate which carries many features of the nearby decay channel. This generic mechanism in open quantum systems explains the phenomenological Ikeda diagram and generalizes it for various clusters/correlations in the vicinity of the respective cluster decay thresholds. The near-threshold collectivization of the SM states may also influence their electromagnetic decays. We discuss this phenomenon on the example of B(EL) decays of near-threshold 2+ states in 14C.

    Comments:
    8 pages, 2 figures, Invited talk at INPC2019
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1910.06526 [pdf]
    J.Phys.Conf.Ser.(2020)·9 citations
  2. 02

    [Submitted on 15 Oct 2019]

    Unraveling the reaction mechanisms leading to partial fusion of weakly bound nuclei

    Jin Lei🇺🇸 · Antonio M. Moro🇪🇸

    Collisions between complex nuclei may give rise to their total or partial fusion. The latter case is found experimentally to gain importance when one of the colliding nuclei is weakly bound. It has been commonly assumed that the partial fusion mechanism is a two-step process, whose first step is the dissociation of the weakly bound nucleus, followed by the capture of one of the fragments. To assess this interpretation, we present the first implementation of the three-body model of inclusive breakup proposed in the 1980s by Austern et al. [Phys. Rep. 154, 125 (1987)] that accounts for both the direct, one-step, partial fusion and the two-step mechanism proceeding via the projectile continuum states. Contrary to the widely assumed picture, we find that, at least for the investigated cases, the partial fusion is largely dominated by the direct capture from the projectile ground-state.

    Comments:
    Accepted for publication in Phys. Rev. Letters
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1910.06625 [pdf]
    PRL(2019)·39 citations
  3. 03

    [Submitted on 15 Oct 2019]

    Static fission properties of actinide nuclei

    P. Jachimowicz · M. Kowal · J. Skalski

    Fission barriers heights and excitation energies of superdeformed isomeric minima are calculated within the microscopic - macroscopic Woods - Saxon model for 75 actinide nuclei for which the experimental data are known. State - of - the - art methods were used: minimization over many deformation parameters for minima and the imaginary water flow on many - deformation energy grid for saddles, including nonaxial and reflection-asymmetric shapes. We obtain 0.82 - 0.94 MeV rms deviation between the calculated and experimental barriers and 0.53 MeV rms error in the excitation of superdeformed minima (SD). Experimental vs theory discrepancies seem to be of various nature and not easy to eliminate, especially if one cares for more than one or two observables. As an example, we show that by strengthening pairing in odd systems one can partially improve agreement in barriers, while spoiling it for masses. We also discuss the "thorium anomaly" and suggest its possible relation to a different way in which the Ac and Th barriers are derived from experimental data.

    Comments:
    Submitted to PRC
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1910.06649 [pdf]
    PRC(2020)·28 citations
  4. 04

    [Submitted on 13 Oct 2019]

    Resolving the Quenched Puzzle in Nuclei and Nuclear Matter

    Mannque Rho🇫🇷

    The long-standing puzzle of the quenched in nuclei -- and in dense matter -- is shown to have a simple resolution in a scale-symmetric HLS chiral Lagrangian at the Fermi-liquid fixed point. This resolution exposes scale-chiral symmetry, hidden in QCD in the vacuum, emerging in nuclear matter from low density to high compact-star density. It has important implications on "first principles" approaches to nuclear physics, such as the role of multi-body exchange currents in Gamow-Teller matrix elements in nuclei and in neutrinoless double decays for going Beyond the Standard Model.

    Comments:
    6 pages, no figures. conclusion sharpened
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1910.06770 [pdf]
    2 citations
  5. 05

    [Submitted on 15 Oct 2019]

    Spin Polarizations in a Covariant Angular-Momentum-Conserved Chiral Transport Model

    Shuai Y.F. Liu🇺🇸 · Yifeng Sun🇮🇹 · Che Ming Ko🇺🇸

    Using a covariant and angular-momentum-conserved chiral transport model, which takes into account the spin-orbit interactions of chiral fermions in their scatterings via the side jumps, we study the quark spin polarization in quark matter. For a system of rotating and unpolarized massless quarks in an expanding box, we find that side jumps can dynamically polarize the quark spin and result in a final quark spin polarization consistent with that of thermally equilibrated massless quarks in a self-consistent vorticity field. For the quark matter produced in noncentral relativistic heavy ion collisions, we find that in the medium rest frame both the quark local spin polarizations in the direction perpendicular to the reaction plane and along the longitudinal beam direction show an azimuthal angle dependence in the transverse plane similar to those observed in experiments for the Lambda hyperon.

    Comments:
    6 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1910.06774 [pdf]
    PRL(2020)·107 citations
  6. 06

    [Submitted on 26 Sept 2019] (cross-list from hep-th)

    Topology of Generalized Spinors and Chiral Anomaly

    Ho-Ung Yee🇺🇸 · Piljin Yi🇰🇷

    Weyl fermions with nonlinear dispersion have appeared in real world systems, such as in the Weyl semi-metals and topological insulators. We consider the most general form of Dirac operators, and study its topological properties embedded in the chiral anomaly, in the index theorem, and in the odd-dimensional partition function, by employing the heat kernel. We find that all of these topological quantities are enhanced by a winding number defined by the Dirac operator in the momentum space, regardless of the spacetime dimensions. The chiral anomaly in , in particular, is also confirmed via the conventional Feynman diagram. These interconnected results allow us to clarify the relationship between the chiral anomaly and the Chern number of the Berry connection, under dispute in some recent literatures, and also lead to a compact proof of the Nielsen-Ninomiya theorem.

    Comments:
    42 pages, 1 figure
    Subjects:
    High Energy Physics — Theory (hep-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
    arXiv:
    1909.12409 [pdf]
    PRD(2020)·10 citations
  7. 07

    [Submitted on 15 Oct 2019] (cross-list from hep-ph)

    Chemical equilibration of QGP in hadronic collisions

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇨🇭

    We performed state-of-the-art QCD effective kinetic theory simulations of chemically equilibrating QGP in longitudinally expanding systems. We find that chemical equilibration takes place after hydrodynamization, but well before local thermalization. By relating the transport properties of QGP and the system size we estimate that hadronic collisions with final state multiplicities live long enough to reach approximate chemical equilibrium for all collision systems. Therefore we expect the saturation of strangeness enhancement to occur at the same multiplicity in proton-proton, proton-nucleus and nucleus-nucleus collisions.

    Comments:
    5 pages, 1 figure, proceedings for the XVIII International Conference on Strangeness in Quark Matter (SQM 2019), based on arXiv:1811.03040, arXiv:1811.03068
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1910.06664 [pdf]
    Springer Proc.Phys.(2020)·2 citations

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first authorsco-authorsvia INSPIRE