Nuclear Theory·nucl-th

Wednesday·July 15, 2020

17 papers—9 primary·8 cross-listed

01
[Submitted on 13 Jul 2020]
Satisfying the compressibility sum rule in neutron matter
Mateusz Buraczynski · Samuel Martinello · Alexandros Gezerlis
The static-response function of strongly interacting neutron matter contains crucial information on this interacting many-particle system, going beyond ground-state properties. In the present work, we tackle this problem with quantum Monte Carlo (QMC) approaches at several different densities, using both phenomenological forces and (for the first time) chiral effective field theory interactions. We handle finite-size effects via self-consistent energy-density functional (EDF) calculations for 8250 particles in a periodic volume. We combine these QMC and EDF computations in an attempt to produce a model-independent extraction of the static response function. Our results are consistent with the compressibility sum rule, which encapsulates the limiting behavior of the response function starting from the homogeneous equation of state, without using the sum rule as an input constraint. Our predictions on inhomogeneous neutron matter can function as benchmarks for other many-body approaches, thereby shedding light on the physics of neutron-star crusts and neutron-rich nuclei.
Comments:
6 pages, 3 figures; v3 corresponds to published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas)
arXiv:
2007.06589 [pdf]
PLB(2021)·9 citations
02
[Submitted on 13 Jul 2020]
Charge radii of exotic neon and magnesium isotopes
S. J. Novario · G. Hagen · G. R. Jansen · T. Papenbrock
We compute the charge radii of even-mass neon and magnesium isotopes from neutron number N = 8 to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon potentials from chiral effective field theory that include delta isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data and the dripline in neon is accurate. The computed charge radii have an estimated uncertainty of about 2-3% and are accurate for many isotopes where data exist. Finer details such as isotope shifts, however, are not accurately reproduced. Chiral potentials correctly yield the subshell closure at N = 14 and also a decrease in charge radii at N = 8 (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond N = 14 yet underestimate the large increase at N = 20 in magnesium.
Comments:
9 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.06684 [pdf]
PRC(2020)·106 citations
03
[Submitted on 14 Jul 2020]
Proton induced deuteron knockout reaction as a probe of an isoscalar proton-neutron pair in nuclei
Yoshiki Chazono · Kenichi Yoshida · Kazuki Yoshida · Kazuyuki Ogata
The isoscalar $p n$ pair is expected to emerge in nuclei having the similar proton and neutron numbers but there is no clear experimental evidence for it. We aim to clarify the correspondence between the $p n$ pairing strength in many-body calculation and the triple differential cross section (TDX) of proton-induced deuteron knockout ( $p, p d$ ) reaction on $^{16}$ O. The radial wave function of the isoscalar $p n$ pair with respect to the center of $^{16}$ O is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation (DWIA) framework. The $p n$ pairing strength $V_{0}$ in the EDF calculation is varied and the corresponding change in the TDX is investigated. A clear $V_{0}$ dependence of the TDX is found for the $^{16}$ O( $p, p d$ ) $^{14}$ N( $1_{2}^{+}$ ) at $101.3$ MeV. The nuclear distortion is found to make the $V_{0}$ dependence stronger. Because of the clear $V_{0}$ -TDX correspondence, the ( $p, p d$ ) reaction will be a promising probe for the isoscalar $p n$ pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.
Comments:
7 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.06771 [pdf]
PRC(2021)·5 citations
04
[Submitted on 14 Jul 2020]
Nucleon localization function in rotating nuclei
Tong Li · Mengzhi Chen · Chunli Zhang · Witold Nazarewicz · Markus Kortelainen
Background: An electron localization function was originally introduced to visualize bond structures in molecules. It became a useful tool to describe electron configurations in atoms, molecules and solids. In nuclear physics, a nucleon localization function (NLF) has been used to characterize clusters in light nuclei, fragment formation in fission and pasta phases in the inner crust of neutron stars. Purpose: We use the NLF to study the nuclear response to fast rotation. Methods: We generalize the NLF to the case of nuclear rotation. The extended expressions involve both time-even and time-odd local densities. Since current density and density gradient contribute to the NLF primarily at the surface, we propose a simpler spatial measure given by the kinetic-energy density. Illustrative calculations for the superdeformed yrast band of $^{152}$ Dy were carried out by using the cranked Skyrme-Hartree-Fock method. We also employed the cranked harmonic-oscillator model to gain insights into patterns revealed by the NLF at high angular momentum. Results: In a deformed rotating nucleus, several NLFs can be introduced, depending on the definition of the spin-quantization axis and self-consistent symmetries of the system. The oscillating pattern of the NLF can be explained by a constructive interference between the kinetic-energy and particle densities. The nodal pattern seen in the NLF along the major axis of a rotating nucleus comes from single-particle orbits with large aligned angular momentum. The variation of the NLF along the minor axis is traced back to deformation-aligned orbits. Conclusions: The NLF allows a simple interpretation of the shell structure evolution in the rotating nucleus in terms of the angular-momentum alignment of individual nucleons. We expect that the NLF will be useful for the characterization of other collective modes and time-dependent processes.
Comments:
14 pages, 20 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.06797 [pdf]
PRC(2020)·10 citations
05
[Submitted on 14 Jul 2020]
From nuclei to neutron stars: simple binding energy computer modelling in the classroom (Part 1)
A. Pastore · A. M. Romero · C. Diget · A. Rios · K. Leech · P. Stokoe
We present a simple activity based on the liquid-drop model which allows secondary school students to explore the uses of mathematical models and gain an intuitive understanding of the concept of binding energy, and in particular the significance of positive binding energy. Using spreadsheets provided as Supplementary Material, students can perform simple manipulations on the different coefficients of the model to understand the role of each of its five terms. Students can use the spreadsheets to determine model parameters by optimising the agreement with real atomic mass data. %This will subsequently be used to predict the limit of existence of the Segré chart and to find the minimum mass of a neutron star. This activity can be used as the starting point of a discussion about theoretical models, their validation when it comes to describing experimental data and their predictive power towards unexplored regimes.
Comments:
Published Physics Education 56 (3), 035012
Subjects:
Nuclear Theory (nucl-th); physics.ed-ph (physics.ed-ph)
arXiv:
2007.06872 [pdf]
Phys.Educ.(2021)·2 citations
06
[Submitted on 14 Jul 2020]
Spinodal instabilities of spin polarized asymmetric nuclear matter
Artur Polls · Isaac Vidana
We analyze the spinodal instabilities of spin polarized asymmetric nuclear matter at zero temperature for several configurations of the neutron and proton spins. The calculations are performed with the Brueckner--Hartree--Fock (BHF) approach using the Argonne V18 nucleon-nucleon potential plus a three-nucleon force of Urbana type. An analytical parametrization of the energy density, which reproduces with good accuracy the BHF results, is employed to determine the spinodal instability region. We find that, independently of the of the orientation of the neutron and proton spins, the spinodal instability region shinks when the system is polarized, being its size smaller smaller when neutron and proton spins are antiparallel than when they are oriented in a parallel way. We find also that the spinodal instability is always dominated by total density fluctuation independently of the degree of polarization of the system, and that restoration of the isospin symmetry in the liquid phase, {\it i.e.,} the so-called isospin distillation or fragmentation effect, becomes less efficient with the polarization of the system.
Comments:
8 pages, 6 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2007.06900 [pdf]
PRC(2020)·1 citation
07
[Submitted on 14 Jul 2020]
Analysis of the $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ astrophysical direct capture reactions in a modified potential-model approach
E.M. Tursunov · S.A. Turakulov · A.S. Kadyrov
Astrophysical $S$ factors and reaction rates of the direct radiative capture processes $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ , as well as the primordial abundance of the $^{7} Li$ element, are estimated in the framework of a modified two-body potential model. It is shown that suitable modification of phase-equivalent $α -^{3} He$ potentials in the $d$ waves can improve the description of the astrophysical $S$ factor for the direct $^{3} He (α, γ)^{7} Be$ radiative capture reaction at energies above 0.5 MeV. An estimated $^{7} Li/H$ abundance ratio of $(4.89 \pm 0.18) \times 1 0^{- 10}$ is in very good agreement with the recent measurement of $(5.0 \pm 0.3) \times 1 0^{- 10}$ by the LUNA collaboration.
Comments:
22 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Experiment (nucl-ex)
arXiv:
2007.06952 [pdf]
NPA(2021)·15 citations
08
[Submitted on 12 Jul 2020]
Stable bound states of $N$ 's, $Λ$ 's, and $Ξ$ 's
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
We review our recent work about the stability of strange few-body systems containing $N$ 's, $Λ$ 's, and $Ξ$ 's. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESC08c Nijmegen potentials. We solve the three- and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, $Λ n p$ $(I) J^{P} = (1/2) 1/ 2^{+}$ , is bound by 144 keV; the recently discussed $Λ nn$ $(I) J^{P} = (1/2) 1/ 2^{+}$ system is unbound, as well as the $ΛΛ nn$ $(I) J^{P} = (1) 0^{+}$ system, being just above threshold. Our results indicate that the $Ξ N N$ , $ΞΞ N$ and $ΞΞ N N$ systems with maximal isospin might be bound.
Comments:
24 pages, 14 figures. arXiv admin note: substantial text overlap with arXiv:1703.09067, arXiv:1606.08767
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2007.07080 [pdf]
Rev. Mex. F\'is. 63, 411-422 (2017)·0 citations
09
[Submitted on 14 Jul 2020]
Insights into nuclear saturation density from parity violating electron scattering
C. J. Horowitz🇺🇸 · J. Piekarewicz🇺🇸 · Brendan Reed🇺🇸
The saturation density of nuclear matter $ρ_{0}$ is a fundamental nuclear physics property that is difficult to predict from fundamental principles. The saturation density is closely related to the interior density of a heavy nucleus, such as $^{208}$ Pb. We use parity violating electron scattering to determine the average interior weak charge and baryon densities in $^{208}$ Pb. This requires not only measuring the weak radius $R_{wk}$ but also determining the surface thickness of the weak charge density $a$ . We obtain $ρ_{0} = 0.150 \pm 0.010$ fm $^{- 3}$ , where the 7\% error has contributions form the PREX error on the weak radius, an assumed 10\% uncertainty in the surface thickness $a$ , and from the extrapolation to infinite nuclear matter. These errors can be improved with the upcoming PREX II results and with a new parity violating electron scattering experiment, at a somewhat higher momentum transfer, to determine $a$ .
Comments:
6 pages, 3 figures, minor changes, Phys. Rev. C in press
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2007.07117 [pdf]
PRC(2020)·56 citations

Affiliations

first authorsco-authorsvia INSPIRE