Nuclear Theory·nucl-th

Thursday·October 24, 2019

10 papers—7 primary·3 cross-listed

01
[Submitted on 23 Oct 2019]
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.
Comments:
4 pages, 9 references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.10422 [pdf]
Eur.Phys.J.Plus(2020)·0 citations
02
[Submitted on 23 Oct 2019]
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.
Comments:
9 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.10500 [pdf]
PLB(2020)·4 citations
03
[Submitted on 23 Oct 2019]
Ground state properties and potential energy surfaces of $^{270}$ 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 $^{270}$ 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. $^{270}$ 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 $^{270}$ 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 $^{270}$ 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.
Comments:
13 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.10552 [pdf]
SCPMA(2020)·34 citations
04
[Submitted on 23 Oct 2019]
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.
Comments:
14 pages, 10 figures; Title changed. Published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1910.10556 [pdf]
PRC(2020)·74 citations
05
[Submitted on 23 Oct 2019]
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 $^{1} S_{0}$ and $^{3} S_{1}$ 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.
Comments:
8 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Quantum Physics (quant-ph)
arXiv:
1910.10560 [pdf]
PLB(2020)·7 citations
06
[Submitted on 23 Oct 2019]
Asymptotic normalization coefficients from transfer reaction and R-martix analysis of direct capture in $^{22}$ Ne(p, $γ$ ) $^{23}$ Na reaction
Rajkumar Santra · Suprita Chakraborty · Subinit Roy
The $^{22}$ Ne(p, $γ$ ) $^{23}$ Na reaction in NeNa cycle plays an important role in the production of only stable sodium isotope $^{23}$ 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 $_{O}$ $\leq$ M $\leq$ 6 M $_{O}$ ). 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 $_{p}$ = 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 $^{23}$ 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 $^{23}$ Na. A finite range distorted wave Born approximation (FRDWBA) calculation has been performed for $^{22}$ Ne( $^{3}$ He,d) $^{23}$ 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 $_{t o t}^{D C}$ (0) = 48.8 $\pm$ 9.5 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 $\leq$ T $\leq$ 0.2 GK temperature range but otherwise in agreeent with Ferraro, {\it et al.}.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1910.10570 [pdf]
PRC(2020)·7 citations
07
[Submitted on 23 Oct 2019]
Sub Coulomb barrier d+ $^{208}$ 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 $^{208}$ 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 ( $E1$ ) 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 $E1$ interaction during the scattering becomes increasingly significant at higher bombarding energies.
Comments:
12 pages, 6 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1910.10586 [pdf]
J.Phys.G(2022)·9 citations
08
[Submitted on 22 Oct 2019] (cross-list from hep-ph)
Power Counting the Small- $x$ Observables
Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳
We emphasize the importance of applying power counting to the small- $x$ observables, which introduces novel soft contributions usually missing and allows for a unified treatment of the Balitsky-Kovchegov (BK) evolution and various Sudakov logarithms. We use $p A \to h (p_{h ⊥}) X$ at forward rapidity to highlight how the power counting yields a partonic cross section with collinear and soft sectors. We show how the kinematic constraints can be obtained in the soft sector without violating the power counting. We further show how one can resum the threshold Sudakov logarithms systematically to all orders in a re-factorized framework with additional collinear-soft contributions. Direct applications to other small- $x$ processes involving heavy particles, jet (sub-)observables and EIC physics are straightforward.
Comments:
5 pages, 2 figures, statements clarified and references added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1910.10166 [pdf]
13 citations
09
[Submitted on 23 Oct 2019] (cross-list from hep-ph)
$Ω$ baryon spectrum and their decays in a constituent quark model
Ming-Sheng Liu🇨🇳 · Kai-Lei Wang🇨🇳 · Qi-Fang Lü🇨🇳 · Xian-Hui Zhong🇨🇳
Combining the recent developments of the observations of $Ω$ sates we calculate the $Ω$ spectrum up to the $N = 2$ shell within a nonrelativistic constituent quark potential model. Furthermore, the strong and radiative decay properties for the $Ω$ resonances within the $N = 2$ shell are evaluated by using the masses and wave functions obtained from the potential model. It is found that the newly observed $Ω (2012)$ resonance is most likely to be the spin-parity $J^{P} = 3/ 2^{-}$ $1 P$ -wave state $Ω (1^{2} P_{3/ 2^{-}})$ , it also has a large potential to be observed in the $Ω (1672) γ$ channel. Our calculation shows that the 1 $P$ -, 1 $D$ -, and 2 $S$ -wave $Ω$ baryons have a relatively narrow decay width of less than 50 MeV. Based on the obtained decay properties and mass spectrum, we further suggest optimum channels and mass regions to find the missing $Ω$ resonances via the strong and/or radiative decay processes.
Comments:
12 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1910.10322 [pdf]
PRD(2020)·57 citations
10
[Submitted on 23 Oct 2019] (cross-list from hep-ph)
The evolution of Information entropy components in Relativistic Heavy-Ion Collisions
Fei Li🇨🇳 · Gang Chen🇨🇳
Shannon information entropy provides an effective tool to study the evolution process in relativistic heavy-ion collisions. The time evolution process of thermodynamic entropy $S_{thermal}$ , multiple entropy $S_{mul}$ , and configuration entropy $S_{conf}$ at RHIC is studied using the AMPT model to generate central Au-Au collisions. By superimposing the three kinds of information entropy, we can get a more complete information entropy of the system to describe the physical information of the relativistic heavy ion collision. The results show that the four stages of the time evolution process of the system entropy $S$ seem to correspond to the four physical processes in the relativistic heavy ion collision, indicating that the total entropy of the system can reflect the physical information in the relativistic heavy ion collision more accurately.
Comments:
7 pages,8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1910.10420 [pdf]
EPJA(2020)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE