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Nuclear Theory·nucl-th

Friday·February 26, 2016

15 papers—7 primary·8 cross-listed

All15Primary7Cross-lists8
  1. 01

    [Submitted on 24 Feb 2016]

    From Bethe-Salpeter Wave Functions to Generalised Parton Distributions

    C. Mezrag🇺🇸 · H. Moutarde🇫🇷 · J. Rodriguez-Quintero🇪🇸

    We review recent works on the modelling of Generalised Parton Distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. Specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within this framework, in a two-body approximation.

    Comments:
    Review paper, 52 pages, 20 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1602.07722 [pdf]
    Few Body Syst.(2016)·68 citations
  2. 02

    [Submitted on 25 Feb 2016]

    Investigating multi-channel quantum tunneling in heavy-ion fusion reactions with Bayesian spectral deconvolution

    K. Hagino

    Excitations of colliding nuclei during a nuclear reaction considerably affect fusion cross sections at energies around the Coulomb barrier. It has been demonstrated that such channel coupling effects can be represented in terms of a distribution of multiple fusion barriers. We here apply a Bayesian approach to analyze the so called fusion barrier distributions. This method determines simultaneously the barrier parameters and the number of barriers. We particularly investigate the O+Sm and O+Sm systems in order to demonstrate the effectiveness of the method. The present analysis indicates that the fusion barrier distribution for the former system is most consistent with three fusion barriers, even though the experimental data show only two distinct peaks.

    Comments:
    6 pages, 4 eps figures. The version to appear in Phys. Rev. C (rapid communications)
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Data Analysis, Statistics and Probability (physics.data-an)
    arXiv:
    1602.07801 [pdf]
    PRC(2016)·8 citations
  3. 03

    [Submitted on 25 Feb 2016]

    Large-scale shell-model analysis of the neutrinoless decay of Ca

    Y. Iwata🇯🇵 · N. Shimizu🇯🇵 · T. Otsuka🇯🇵 · Y. Utsuno🇯🇵 · J. Menendez🇯🇵 · M. Honma🇯🇵 · T. Abe🇯🇵

    We present the nuclear matrix element for the neutrinoless double-beta decay of Ca based on large-scale shell-model calculations including two harmonic oscillator shells ( and shells). The excitation spectra of Ca and Ti, and the two-neutrino double-beta decay of Ca are reproduced in good agreement to experiment. We find that the neutrinoless double-beta decay nuclear matrix element is enhanced by about 30\% compared to -shell calculations. This reduces the decay lifetime by almost a factor of two. The matrix-element increase is mostly due to pairing correlations associated with cross-shell - excitations. We also investigate possible implications for heavier neutrinoless double-beta decay candidates.

    Comments:
    Phys. Rev. Lett., accepted
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1602.07822 [pdf]
    PRL(2016)·108 citations
  4. 04

    [Submitted on 25 Feb 2016]

    Thermal QRPA with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions

    Alan A. Dzhioev · A. I. Vdovin · G. Martínez-Pinedo · J. Wambach · Ch. Stoyanov

    The Thermal Quasiparticle Random-Phase Approximation is combined with the Skyrme energy density functional method (Skyrme-TQRPA) to study the response of a hot nucleus to an external perturbation. For the sample nuclei, Fe and Ge, the Skyrme-TQRPA is applied to analyze thermal effects on the strength function of charge-neutral Gamow-Teller transitions which dominate neutrino-nucleus reactions at ~MeV. For the relevant supernova temperatures we calculate the cross sections for inelastic neutrino scattering. We also apply the method to examine the rate of neutrino-antineutrino pair emission by hot nuclei. The cross sections and rates are compared with those obtained earlier from the TQRPA calculations based on the phenomenological Quasiparticle-Phonon Model Hamiltonian. For inelastic neutrino scattering on Fe we also compare the Skyrme-TQRPA results to those obtained earlier from a hybrid approach that combines shell-model and RPA calculations.

    Comments:
    Minor revisions according to referee's recomendations
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1602.07869 [pdf]
    PRC(2016)·24 citations
  5. 05

    [Submitted on 25 Feb 2016]

    The Skyrme-TQRPA calculations of electron capture on hot nuclei in pre-supernova environment

    Alan A. Dzhioev · A. I. Vdovin · Ch. Stoyanov

    We combine the thermal QRPA approach with the Skyrme energy density functional theory (Skyrme-TQRPA) for modelling the process of electron capture on nuclei in supernova environment. For a sample nucleus, Fe, the Skyrme-TQRPA approach is applied to analyze thermal effects on the strength function of GT transitions which dominate electron capture at ~MeV. Several Skyrme interactions are used in order to verify the sensitivity of the obtained results to the Skyrme force parameters. Finite-temperature cross sections are calculated and the results are compared with those of the other model calculations.

    Comments:
    4 figures. arXiv admin note: text overlap with arXiv:1602.07869
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1602.07875 [pdf]
    Phys.Atom.Nucl.(2016)·7 citations
  6. 06

    [Submitted on 25 Feb 2016]

    Regulator Artifacts in Uniform Matter for Chiral Interactions

    A. Dyhdalo🇺🇸 · R.J. Furnstahl🇺🇸 · K. Hebeler🇩🇪 · I. Tews🇩🇪

    Regulator functions applied to two- and three-nucleon forces are a necessary ingredient in many-body calculations based on chiral effective field theory interactions. These interactions have been developed recently with a variety of different cutoff forms, including regulating both the momentum transfer (local) and the relative momentum (nonlocal). While in principle any regulator that suppresses high momentum modes can be employed, in practice artifacts are inevitable in current power counting schemes. Artifacts from particular regulators may cause significant distortions of the physics or may affect many-body convergence rates, so understanding their nature is important. Here we characterize the differences between cutoff effects using uniform matter at Hartree-Fock and second-order in the interaction as a testbed. This provides a clean laboratory to isolate phase-space effects of various regulators on both two- and three-nucleon interactions. We test the normal-ordering approximation for three-nucleon forces in nuclear matter and find that the relative size of the residual 3N contributions is sensitive to the employed regularization scheme.

    Comments:
    29 pages, 27 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1602.08038 [pdf]
    PRC(2016)·65 citations
  7. 07

    [Submitted on 25 Feb 2016]

    Towards Quantum Transport for Central Nuclear Reactions

    Pawel Danielewicz (MSU NSCL) · Arnau Rios (U Surrey) · Brent Barker (Roosevelt U)

    Nonequilibrium Green's functions represent a promising tool for describing central nuclear reactions. Even at the single-particle level, though, the Green's functions contain more information that computers may handle in the foreseeable future. In this study, we explore slab collisions in one dimension, first in the mean field approximation and demonstrate that only function elements close to the diagonal in arguments are relevant, in practice, for the reaction calculations. This bodes well for the application of the Green's functions to the reactions. Moreover we demonstrate that an initial state for a reaction calculation may be generated through adiabatic transformation of interactions. Finally, we report on our progress in incorporating correlations into the dynamic calculations.

    Comments:
    Contribution to Proc Workshop on Progress in Nonequilibrium Green's Functions VI, Lund U, Sweden, Aug 17-21, 2015, ed. C. Verdozzi; 13 pages, 13 figures. arXiv admin note: text overlap with arXiv:0906.4841
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1602.08047 [pdf]
    J.Phys.Conf.Ser.(2016)·0 citations

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first authorsco-authorsvia INSPIRE