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Nuclear Theory·nucl-th

Friday·October 14, 2016

6 papers—5 primary·1 cross-listed

All6Primary5Cross-lists1
  1. 01

    [Submitted on 13 Oct 2016]

    Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions

    Y. Chiba · Y. Taniguchi · M. Kimura

    [Background] Various cluster states of astrophysical interest are expected to exist in the excited states of . However, they have not been identified firmly, because of the experimental and theoretical difficulties. [Purpose] To establish the Mg+, O+C and Ne+2 cluster bands, we theoretically search for the negative-parity cluster bands that are paired with the positive-parity bands to constitute the inversion doublets. We also offer the isoscalar monopole and dipole transitions as a promising probe for the clustering. We numerically show that these transition strengths from the ground state to the cluster states are very enhanced. [Method] The antisymmetrized molecular dynamics with Gogny D1S effective interaction is employed to calculate the excited states of . The isoscalar monopole and dipole transition strengths are directly evaluated from wave functions of the ground and excited states. [Results] Negative-parity bands having Mg+ and O+C cluster configurations are obtained in addition to the newly calculated Ne+2 cluster bands. All of them are paired with the corresponding positive-parity bands to constitute the inversion doublets with various cluster configurations. The calculation show that the band-head of the Mg+ and Ne+2 cluster bands are strongly excited by the isoscalar monopole and dipole transitions. [Conclusions] The present calculation suggests the existence of the inversion doublets with the Mg+, O+C and Ne+2 configurations.Because of the enhanced transition strengths, we offer the isoscalar monopole and dipole transitions as good probe for the Mg+ and Ne+2 cluster bands.

    Comments:
    28 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1610.04000 [pdf]
    PRC(2017)·24 citations
  2. 02

    [Submitted on 13 Oct 2016]

    amplitudes below threshold constrained by multinucleon absorption

    E. Friedman🇮🇱 · A. Gal🇮🇱

    Six widely different subthreshold scattering amplitudes obtained in SU(3) chiral-model EFT approaches by fitting to low-energy and threshold data are employed in optical-potential studies of kaonic atoms. Phenomenological terms representing multinucleon interactions are added to the EFT inspired single-nucleon part of the -nucleus optical potential in order to obtain good fits to kaonic-atom strong-interaction level shifts and widths across the periodic table. Introducing as a further constraint the fractions of single-nucleon absorption at rest from old bubble-chamber experiments, it is found that only two of the models considered here reproduce these absorption fractions. Within these two models, the interplay between single-nucleon and multinucleon interactions explains features observed previously with fully phenomenological optical potentials. Radial sensitivities of kaonic atom observables are also re-examined, and remarks are made on the role of `subthreshold kinematics' in absorption at rest calculations.

    Comments:
    24 pages, 7 figures, 5 tables; slightly extended discussion. Nucl. Phys. A in press
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1610.04004 [pdf]
    NPA(2017)·57 citations
  3. 03

    [Submitted on 13 Oct 2016]

    Combining symmetry breaking and restoration with configuration interaction: a highly accurate many-body scheme applied to the pairing Hamiltonian

    J. Ripoche🇫🇷 · D. Lacroix🇫🇷 · D. Gambacurta🇷🇴 · J.-P. Ebran🇫🇷 · T. Duguet🇧🇪

    Background: Ab initio many-body methods have been developed over the past ten years to address mid-mass nuclei... As progress in the design of inter-nucleon interactions is made, further efforts must be made to tailor many-body methods. Methods: We formulate a truncated configuration interaction method that consists of diagonalizing the Hamiltonian in a highly truncated subspace of the total N-body Hilbert space. The reduced Hilbert space is generated via the particle-number projected BCS state along with projected seniority-zero two and four quasi-particle excitations. Furthermore, the extent by which the underlying BCS state breaks U(1) symmetry is optimized in presence of the projected two and four quasi-particle excitations... The quality of the newly designed method is tested against exact solutions of the so-called attractive pairing Hamiltonian problem. Results: By construction, the method reproduce exact results for N=2 and N=4. For N=(8,16,20) the error on the ground-state correlation energy is less than (0.006, 0.1, 0.15) % across the entire range of inter-nucleon coupling defining the pairing Hamiltonian and driving the normal-to-superfluid quantum phase transition. The presently proposed method offers the advantage to automatically access the low-lying spectroscopy, which it does with high accuracy. Conclusions: The numerical cost of the newly designed variational method is polynomial (N) in system size. It achieves an unprecedented accuracy on the ground-state correlation energy, effective pairing gap and one-body entropy as well as on the excitation energy of low-lying states of the attractive pairing Hamiltonian. This constitutes a strong enough motivation to envision its application to realistic nuclear Hamiltonians in view of providing a complementary, accurate and versatile ab initio description of mid-mass open-shell nuclei in the future.

    Comments:
    15 pages, 11 figures, full abstract available in text
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el)
    arXiv:
    1610.04063 [pdf]
    PRC(2017)·17 citations
  4. 04

    [Submitted on 13 Oct 2016]

    The Wigner function and short-range correlations in the deuteron

    Thomas Neff · Hans Feldmeier

    The deuteron shows the essential features of short-range correlations found in all nuclei. Experimental observables related to short-range correlations are connected with the high-momentum components of one- and two-body momentum distributions. An intuitive understanding of short-range correlations is provided by the suppression of the two-body density in coordinate space at small distances. The Wigner function provides a quasi-probability distribution in phase-space that allows to investigate short-range correlations as a function of distance and relative momentum in a unified picture. The Wigner function for the deuteron is calculated for bare and SRG evolved AV8' and N3LO interactions and investigated as a function of distance, relative momentum and angular orientation. Partial momentum and coordinate space distributions are obtained by integrating over parts of phase space. The Wigner function shows a pronounced low-momentum peak that is not affected by short-range correlations and a high-momentum shoulder at small distances that reflects short-range correlations. Oscillations of the Wigner function are related to interference of low- and high-momentum components. Short-range correlations are a truly quantum-mechanical phenomenon caused by interference of low- and high-momentum components in the wave function.

    Comments:
    15 pages, 17 figures
    Subjects:
    Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1610.04066 [pdf]
    5 citations
  5. 05

    [Submitted on 13 Oct 2016]

    Hydrodynamic approach to the centrality dependence of di-hadron correlations

    Wagner M. Castilho🇧🇷 · Wei-Liang Qian🇧🇷 · Fernando G. Gardim🇧🇷 · Yogiro Hama🇧🇷 · Takeshi Kodama🇧🇷

    Measurements of di-hadron azimuthal correlations at different centralities for Au+Au collisions at 200 AGeV were reported by the PHENIX Collaboration. The data were presented for different ranges of transverse momentum. In particular, it was observed that the away-side correlation evolves from double- to a single-peak structure when the centrality decreases. In this work, we show that these features naturally appear as due to an interplay between the centrality-dependent smooth background elliptic flow and the one produced by event-by-event fluctuating peripheral tubes. To compare with the PHENIX data, we also carry out numerical simulations by using a hydrodynamical code NeXSPheRIO, and calculate the correlations by both cumulant and the ZYAM method employed by PHENIX Collaboration. It is shown that our results are in reasonable agreement with the data. A brief discussion on the physical content of the present model and its difference from other viewpoint is also presented.

    Comments:
    11 pages and 3 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1610.04108 [pdf]
    PRC(2017)·11 citations

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first authorsco-authorsvia INSPIRE