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Nuclear Theory·nucl-th

Thursday·October 24, 2019

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 01

    On the boundary conditions for the neutron transport equation

    Paolo Saracco · Nicholas Chentre · Sandra Dulla · Piero Ravetto

    The solution of the linear transport equation used for the study of neutral particle fields requires the imposition of appropriate boundary conditions. The choice of the conditions to impose for an infinite medium is not straightforward. The question has been given different formulations in the literature with various justifications based on some physical reasoning. Some aspects of the question are here analysed, from both the mathematical and the physical point of view. It is concluded that the inspiring golden rule should be the establishment of conditions that do not require any reference to the properties of the specific medium being considered for their justification.

    nucl-thEur.Phys.J.Plus(2020)·0 citations
  2. 02

    Spinodal Instability at the Onset of Collective Expansion in Nuclear Collisions

    Pawel Danielewicz🇺🇸 · Hao Lin (Michigan State U)🇺🇸 · Jirina R. Stone (U Oxford/U Tennessee)🇬🇧 · Yoritaka Iwata (Kansai U)🇯🇵

    Using transport theory to model central Au + Au collisions in the energy region of 20 - 110 MeV/u, at impact parameters b <= 5 fm, we predict a measurable impact of spinoidal instability as the collective expansion sets in with energy. Two transport models are employed, the pBUU model, solving a Boltzmann-Uehling-Uhlenbeck equation, and the Brownian Motion (BM) model, solving a set of Langevin equations to describe the motion of individual nucleons in a noisy nuclear medium. We find without ambiguity, for the first time, that a combination of delayed equilibration, onset of collective expansion and the spinodal instability produces a pair of transient ring structures, made of the projectile and target remnants, with spectator nucleons predicted to end in the entities reminiscent of stones in jewelry, on the rings. The ring structures, calculated in the configuration space and mapped onto the velocity space, could be detected in experimental collective flow data.

    nucl-thnucl-exPLB(2020)·4 citations
  3. 03

    Ground state properties and potential energy surfaces of Hs from multidimensionally-constrained relativistic mean field model

    Xu Meng · Bing-Nan Lu · Shan-Gui Zhou

    We study the ground state properties, potential energy curves and potential energy surfaces of the superheavy nucleus Hs by using the multidimensionally-constrained relativistic mean-field model with the effective interaction PC-PK1. The binding energy, size and shape as well as single particle shell structure corresponding to the ground state of this nucleus are obtained. Hs is well deformed and exhibits deformed doubly magic feature in the single neutron and proton level schemes. One-dimensional potential energy curves and two-dimensional potential energy surfaces are calculated for Hs with various spatial symmetries imposed. We investigate in detail the effects of the reflection asymmetric and triaxial distortions on the fission barrier and fission path of Hs. When the axial symmetry is imposed, the reflection symmetric and reflection asymmetric fission barriers both show a double-hump structure and the former is higher. However, when triaxial shapes are allowed the reflection symmetric barrier is lowered very much and then the reflection symmetric fission path becomes favorable.

    nucl-thnucl-exSCPMA(2020)·34 citations
  4. 04

    Unified description of hadron yield ratios from dynamical core-corona initialization

    Yuuka Kanakubo🇯🇵 · Yasuki Tachibana🇯🇵 · Tetsufumi Hirano🇯🇵

    We develop the dynamical core-corona initialization framework as a phenomenological description of the formation of quark gluon plasma (QGP) fluids in high-energy nuclear collisions. Using this framework, we investigate the fraction of the fluidized energy to the total energy and strange hadron yield ratios as functions of multiplicity and scrutinize the multiplicity scaling of hadron yield ratios recently reported by the ALICE Collaboration. Our results strongly indicate that the QGP fluids are partly formed even at the averaged multiplicity for nonsingle diffractive p+p events.

    nucl-thhep-phnucl-exPRC(2020)·74 citations
  5. 05

    Spectral-shift and scattering-equivalent Hamiltonians on a coarse momentum grid

    María Gómez-Rocha🇪🇸 · Enrique Ruiz Arriola🇪🇸

    The solution of the scattering problem based on the Lippmann-Schwinger equation requires in many cases a discretization of the spectrum in the continuum which does not respect the unitary equivalence of the S-matrix on the finite grid. We present a new prescription for the calculation of phase shifts based on the shift that is produced in the spectrum of a Chebyshev-angle variable. This is analogous to the energy shift that is produced in the energy levels of a scattering process in a box, when an interaction is introduced. Our formulation holds for any momentum grid and preserves the unitary equivalence of the scattering problem on the finite momentum grid. We illustrate this procedure numerically considering the non-relativistic NN case for and channels. Our spectral shift formula provides much more accurate results than the previous ones and turns out to be at least as competitive as the standard procedures for calculating phase shifts.

    nucl-thhep-phquant-phPLB(2020)·7 citations
  6. 06

    Asymptotic normalization coefficients from transfer reaction and R-martix analysis of direct capture in Ne(p,)Na reaction

    Rajkumar Santra · Suprita Chakraborty · Subinit Roy

    The Ne(p,)Na reaction in NeNa cycle plays an important role in the production of only stable sodium isotope Na. This nucleus is processed by the NeNa cycle during hot bottom burning (HBB) in asymptotic giant branch (AGB) stage of low metallicity intermediate mass stats (4 M M 6 M). Recent measurements have addressed the uncertainty in the thermonuclear reaction rate of this reaction at relevant astrophysical energies through the identification of low lying resonances at E = 71,105, 156.2, 189.5 and 259.7 keV. In addition, precise measurements of low energy behaviour of the non-resonant capture has also been performed and the contribution of the sub-threshold resonance at 8664 keV excitation in Na has been established. Here, in this article, we have presented a systematic R-matrix analysis of direct capture to the bound states and the decay of the sub-threshold resonance at 8664 keV to the ground state of Na. A finite range distorted wave Born approximation (FRDWBA) calculation has been performed for Ne(He,d)Na transfer reaction data to extract the asymptotic normalization coeeficients (ANC-s) required to estimate the non-resonant capture cross sections or astrophysical S-factor values in R-matrix analysis. Simultaneous R-matrix analysis constrained with ANC-s from transfer calculation reproduced the astrophysical S-factor data over a wide energy window. The S(0) = 48.89.5 keV.b compares well with the result of Ferraro, {\it et al.} and has a lower uncertainty. The resultant thermonuclear reaction is slightly larger in 0.1 GK T 0.2 GK temperature range but otherwise in agreeent with Ferraro, {\it et al.}.

    nucl-thPRC(2020)·7 citations
  7. 07

    Sub Coulomb barrier d+Pb scattering in the time-dependent basis function approach

    Peng Yin · Weijie Du · Wei Zuo · Xingbo Zhao · James P. Vary

    We employ the non-perturbative time-dependent basis function (tBF) approach to study the scattering of the deuteron on Pb below the Coulomb barrier. We obtain the bound and discretized scattering states of the projectile, which form the basis representation of the tBF approach, by diagonalizing a realistic Hamiltonian in a large harmonic oscillator basis. We find that the higher-order inelastic scattering effects are noticeable for sub barrier scatterings with the tBF method. We have successfully reproduced experimental sub Coulomb barrier elastic cross section ratios with the tBF approach by considering only the electric dipole () component of the Coulomb interaction between the projectile and the target during scatterings. We find that the correction of the polarization potential to the Rutherford trajectory is dominant in reproducing the data at very low bombarding energies, whereas the role of internal transitions of the deuteron projectile induced by the interaction during the scattering becomes increasingly significant at higher bombarding energies.

    nucl-thnucl-exJ.Phys.G(2022)·9 citations

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first authorsco-authorsvia INSPIRE