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Nuclear Theory·nucl-th

Tuesday·November 24, 2015

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 01

    [Submitted on 21 Nov 2015]

    Stochastic Estimation of Nuclear Level Density in the Nuclear Shell Model: An Application to Parity-Dependent Level Density in Ni

    Noritaka Shimizu🇯🇵 · Yutaka Utsuno🇯🇵 · Yasunori Futamura🇯🇵 · Tetsuya Sakurai🇯🇵 · Takahiro Mizusaki🇯🇵 · Takaharu Otsuka🇯🇵

    We introduce a novel method to obtain level densities in large-scale shell-model calculations. Our method is a stochastic estimation of eigenvalue count based on a shifted Krylov-subspace method, which enables us to obtain level densities of huge Hamiltonian matrices. This framework leads to a successful description of both low-lying spectroscopy and the experimentally observed equilibration of and states in Ni in a unified manner.

    Comments:
    13 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.06840 [pdf]
    PLB(2016)·33 citations
  2. 02

    [Submitted on 23 Nov 2015]

    The photoproduction off a neutron

    Xiao-Yun Wang🇨🇳 · Jun He🇨🇳

    Inspired by the preliminary experimental data by the CLAS Collaboration, the photoproduction off a neutron is studied within an effective Lagrangian approach. The contributions from the Born terms including , , and channels are considered to calculate the amplitude, with which the cross sections are calculated and compared with preliminary CLAS data. The theoretical results indicate that the contribution from the -exchange channel plays a dominant role for the photoproduction. The contribution from the exchange is found one order of magnitude smaller than that from the exchange. Both the Regge model and the Feynman model are applied to treat the -channel contribution. The discrepancy between two models is found small in the energy range of CLAS data and predicted to become obvious at energies higher than 3 GeV. More precise experimental data especially at backward angles will be helpful to further understand the interaction mechanism of the photoproduction.

    Comments:
    5 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1511.07141 [pdf]
    PRC(2016)·17 citations
  3. 03

    [Submitted on 23 Nov 2015]

    Symmetry energy and neutron star properties in the saturated Nambu-Jona-Lasinio model

    Si-Na Wei🇨🇳 · Wei-Zhou Jiang🇨🇳 · Rong-Yao Yang🇨🇳 · Dong-Rui Zhang🇨🇳

    In this work, we adopt the Nambu-Jona-Lasinio (NJL) model that ensures the nuclear matter saturation properties to study the density dependence of the symmetry energy. With the interactions constrained by the chiral symmetry, the symmetry energy shows novel characters different from those in conventional mean-field models. First, the negative symmetry energy at high densities that is absent in relativistic mean-field (RMF) models can be obtained in the RMF approximation by introducing a chiral isovector-vector interaction, although it would be ruled out by the neutron star (NS) stability. Second, with the inclusion of the isovector-scalar interaction the symmetry energy exhibits a general softening at high densities even for the large slope parameter of the symmetry energy. The NS properties obtained in the present NJL model can be in accord with the observations. The NS maximum mass obtained with various isovector-scalar couplings and momentum cutoffs is well above the , and the NS radius obtained well meets the limits extracted from recent measurements. In particular, the significant reduction of the canonical NS radius occurs with the moderate decrease of the slope of the symmetry energy.

    Comments:
    7pages,5figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.07144 [pdf]
    PLB(2016)·17 citations
  4. 04

    [Submitted on 23 Nov 2015]

    Effect of correlations on cumulants in heavy-ion collisions

    D. K. Mishra🇮🇳 · P. Garg🇮🇳 · P. K. Netrakanti🇮🇳

    We study the effects of correlations on cumulants and their ratios of net-proton multiplicity distributions which have been measured for central (0\%-5\%) Au + Au collisions at the Relativistic Heavy Ion Collider (RHIC). This effect has been studied assuming individual proton and anti-proton distributions as a Poisson or Negative Binomial Distribution (NBD). In-spite of significantly correlated production due to baryon number, electric charge conservation and kinematical correlations of protons and anti-protons, the measured cumulants of the net-proton distribution follow the independent production model. In the present work we demonstrate how the introduction of the correlations will affect the cumulants and their ratios for the difference distributions. We have also demonstrated this study using the proton and anti-proton distributions obtained from the HIJING event generator.

    Comments:
    7 pages, 9 figures, accepted for publication in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1511.07155 [pdf]
    PRC(2016)·5 citations
  5. 05

    [Submitted on 23 Nov 2015]

    Cooperative internal conversion process

    Péter Kálmán · Tamás Keszthelyi

    A new phenomenon, called cooperative internal conversion process, in which the coupling of bound-free electron and neutron transitions due to the dipole term of their Coulomb interaction permits cooperation of two nuclei leading to neutron exchange if it is allowed by energy conservation, is discussed theoretically. General expression of the cross section of the process is reported in one particle nuclear and spherical shell models as well in the case of free atoms (e.g. noble gases). A half-life characteristic of the process is also determined. The case of is investigated numerically. The process may have significance in fields of nuclear waste disposal and nuclear energy production.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.07164 [pdf]
    1 citation
  6. 06

    [Submitted on 23 Nov 2015]

    Hydrodynamical noise and Gubser flow

    Li Yan🇫🇷 · Hanna Grönqvist🇫🇷

    Hydrodynamical noise is introduced on top of Gubser's analytical solution to viscous hydrodynamics. With respect to the ultra-central collision events of Pb-Pb, p-Pb and p-p at the LHC energies, we solve the evolution of noisy fluid systems and calculate the radial flow velocity correlations. We show that the absolute amplitude of the hydrodynamical noise is determined by the multiplicity of the collision event. The evolution of azimuthal anisotropies, which is related to the generation of harmonic flow, receives finite enhancements from hydrodynamical noise. Although it is strongest in the p-p systems, the effect of hydrodynamical noise on flow harmonics is found to be negligible, especially in the ultra-central Pb-Pb collisions. For the short-range correlations, hydrodynamical noise contributes to the formation of a near-side peak on top of the correlation structure originated from initial state fluctuations. The shape of the peak is affected by the strength of hydrodynamical noise, whose height and width grow from the Pb-Pb system to the p-Pb and p-p systems.

    Comments:
    22 pages and 4 figures. Text and figures updated. New references added. Version to appear in JHEP
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1511.07198 [pdf]
    JHEP(2016)·31 citations
  7. 07

    [Submitted on 23 Nov 2015]

    Tensor-optimized antisymmetrized molecular dynamics in nuclear physics

    Takayuki Myo · Hiroshi Toki · Kiyomi Ikeda · Hisashi Horiuchi · Tadahiro Suhara

    We develop a new formalism to treat nuclear many-body systems using bare nucleon-nucleon interaction. It has become evident that the tensor interaction plays important role in nuclear many-body systems due to the role of the pion in strongly interacting system. We take the antisymmetrized molecular dynamics (AMD) as a basic framework and add a tensor correlation operator acting on the AMD wave function using the concept of the tensor-optimized shell model (TOSM). We demonstrate a systematical and straightforward formulation utilizing the Gaussian integration and differentiation method and the antisymmetrization technique to calculate all the matrix elements of the many-body Hamiltonian. We can include the three-body interaction naturally and calculate the matrix elements systematically in the progressive order of the tensor correlation operator. We call the new formalism "tensor-optimized antisymmetrized molecular dynamics".

    Comments:
    36 pages
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1511.07224 [pdf]
    PTEP(2015)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE