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Nuclear Theory·nucl-th

Monday·March 18, 2019

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 01

    [Submitted on 14 Mar 2019]

    Self-consistent calculation of the reactor antineutrino spectra including forbidden transitions

    J. Petković · T. Marketin · G. Martínez-Pinedo · N. Paar

    With the goal of determining the neutrino oscillation mixing angle, the measurements of reactor antineutrino fluxes at the Double Chooz, RENO and Daya Bay experimental facilities have uncovered a systematic discrepancy between the number of observed events and theoretical expectations. In the \emph{ab initio} approach, the total reactor antineutrino spectrum is a weighted sum of spectra resulting from all branches of all fission products in the reactor core. At all three facilities a systematic deviation of the number of observed events from the number of predicted events was noticed, i.e., approximately 6\% of the predicted neutrinos were not observed. This discrepancy was named the reactor neutrino anomaly. In theoretical studies it is assumed that all the decays are allowed in shape, but a quarter of all transitions are actually forbidden and may have a complex energy dependence that will affect the total reactor antineutrino spectrum. In order to estimate the effect of forbidden transitions, we perform a fully self-consistent calculation of spectra from all contributing transitions and compare the results with a purely allowed approximation.

    Comments:
    10 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1903.06192 [pdf]
    J.Phys.G(2019)·8 citations
  2. 02

    [Submitted on 14 Mar 2019]

    Monopole moments and nuclear compressibility

    G.F. Bertsch

    The nuclear compressibility has a role in nuclear physics in several ways. Its relationship to the giant monopole is well known and has been subject of much theoretical work. Less well known is its affect on in nuclear structure, namely monopole transitions between low-lying states in the spectrum. Here I revisit the relationship between monopole and quadrupole moments in deformed nuclei. It has often been assumed without any microscopic justification that the nucleus can be treated as an incompressible fluid. An analytic formula is derived here for the resulting relationship between monopole and quadrupole moments. The formula is shown to be well satisfied within self-consistent mean-field theory calculated with several energy functionals. The formula can be tested when both monopole and quadrupole matrix elements of band-to-band transitions are known. Data is available for the decay of the first excited band to the ground-state band in Gd, and the extracted matrix elements are found to be consistent with the incompressible fluid picture.

    Comments:
    Original version was submitted to the topical EPJA issue Giant,Pygmy ,Pairing Resonances and Related Topics
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1903.06223 [pdf]
    0 citations
  3. 03

    [Submitted on 15 Mar 2019]

    Relating eccentricity fluctuations to density fluctuations in heavy-ion collisions

    Rajeev S. Bhalerao🇮🇳 · Giuliano Giacalone🇫🇷 · Pablo Guerrero-Rodríguez🇪🇸 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷

    The magnitude of anisotropic flow in a nucleus-nucleus collision is determined by the energy density field, , created right after the collision occurs. Specifically, elliptic flow, , and triangular flow, , are proportional to the anisotropy coefficients and , which are functionals of . We express the mean and the variance of and as a function of the 1- and 2-point functions of . These results generalize results obtained previously, that were valid only for central collisions, or only for identical point-like sources. We apply them to the color glass condensate effective theory, using the recently derived expression of the 2-point function.

    Comments:
    12 pages, 2 figures. v2: minor changes in figures, acknowledgments added. Proceedings of XXV Epiphany conference on Advances in Heavy Ion Physics, Cracow, Poland, 8-11 January 2019
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1903.06366 [pdf]
    Acta Phys.Polon.B(2019)·12 citations
  4. 04

    [Submitted on 15 Mar 2019]

    Time-dependent Hartree-Fock plus Langevin approach for hot fusion reactions to synthesize the superheavy element

    K. Sekizawa · K. Hagino

    We develop a novel approach to fusion reactions for syntheses of superheavy elements, which combines the time-dependent Hartree-Fock (TDHF) method with a dynamical diffusion model based on the Langevin equation. In this approach, the distance of the closest approach for the capture process is estimated within the TDHF approach, which is then plugged into the dynamical diffusion model as an initial condition. We apply this approach to hot fusion reactions leading to formation of the element , that is, the Ca+Fm, V+Bk, and Cr+Cm reactions. Our calculations indicate that the distances of the closest approach for these systems are similar to each other and thus the difference in the probabilities of evaporation residue formation among those reaction systems originates mainly from the evaporation process, which is sensitive to the fission barrier height and the excitation energy of a compound nucleus.

    Comments:
    5 pages, 2 figures, 1 table; published in Physical Review C as a Rapid Communication with Editors' Suggestion
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1903.06386 [pdf]
    PRC(2019)·51 citations
  5. 05

    [Submitted on 15 Mar 2019]

    -rigid triaxial nuclei in the presence of a minimal length via a quantum perturbation method

    S. Ait Elkorchi🇲🇦 · M. Chabab🇲🇦 · A. El Batoul🇲🇦 · A. Lahbas🇲🇦 · M. Oulne🇲🇦

    In this work, we derive a closed solution of the Shrdinger equation for Bohr Hamiltonien within the minimal length formalism. This formalism is inspired by Heisenberg algebra and a generlized uncertainty principle (GUP), applied to the geometrical collective Bohr- Mottelson model (BMM) of nuclei by means of deformed canonical commutation relation and the Pauli-Podolsky prescription. The problem is solved by means conjointly of asymptotic iteration method (AIM) and a quantum perturbation method (QPM) for transitional nuclei near the critical point symmetry Z(4) corresponding to phase transition from prolate to -rigid triaxial shape. A scaled Davidson potentiel is used as a restoring potential in order to get physical minimum. The agreement between the obtained theoretical results and the experimental data is very satisfactory.

    Comments:
    9 pages,1 Figures, LaTeX, contribution to the Proceedings of the 37-th International Workshop on Nuclear Theory (IWNT-37), Rila Mountains, Bulgaria, June 25-July 1, 2018. Editors: M. Gaidarov and N. Minkov, Published by Heron Press Ltd., Sofia, Bulgaria, ISSN 1313-2822
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1903.06504 [pdf]
    Nucl.Theor.(2018)·2 citations
  6. 06

    [Submitted on 14 Mar 2019]

    Extension of Intra-Nuclear Cascade Model to Neutron Induced Nonelastic Cross-Sections in Low Energy Region

    Masahiro Nakano🇯🇵 · Yusuke Uozumi🇯🇵

    Two features, a slow slope and a sharp drop, in neutron induced total nonelastic cross-sections are analyzed within the framework of an intra-nuclear cascade (INC) model. First, to reproduce the slow slope from 100MeV to 10 MeV, the original INC is generalized in two points; a method to construct the ground state of the target nucleus, and a method of taking the effective two body cross-sections between two nucleons. Secondly, to analyze the origin of the sharp drop from 10MeV to nearly 1 MeV, the INC is extended to include quantum effects which are originated from the existence of the discrete states in the nuclear potential. It is shown that this extension leads to the sharp drops in the very low energy below around 10MeV. It is concluded that the INC model can be extended to explain the sharp drops in addition to the slow slope in neutron induced nonelastic cross-sections in the energy region from 100MeV down to 1 MeV.

    Comments:
    The text is 11 pages including 7 figures and 3 tables
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1903.06551 [pdf]
    PRC(2019)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE