Nuclear Theory·nucl-th

Thursday·March 25, 2021

14 papers—11 primary·3 cross-listed

01
[Submitted on 24 Mar 2021]
Nuclear matter in relativistic Brueckner-Hartree-Fock theory with Bonn potential in the full Dirac space
Sibo Wang🇨🇳 · Qiang Zhao🇨🇳 · Peter Ring🇩🇪 · Jie Meng🇨🇳
Starting from the Bonn potential, relativistic Brueckner-Hartree-Fock (RBHF) equations are solved for nuclear matter in the full Dirac space, which provides a unique way to determine the single-particle potentials and avoids the approximations applied in the RBHF calculations in the Dirac space with positive-energy states (PESs) only. The uncertainties of the RBHF calculations in the Dirac space with PESs only are investigated, and the importance of the RBHF calculations in the full Dirac space is demonstrated. In the RBHF calculations in the full Dirac space, the empirical saturation properties of symmetric nuclear matter are reproduced, and the obtained equation of state agrees with the results based on the relativistic Green's function approach up to the saturation density.
Comments:
25 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.12960 [pdf]
PRC(2021)·50 citations
02
[Submitted on 24 Mar 2021]
Squeezed spectra of bosons and antibosons with different in-medium masses
Yong Zhang🇨🇳 · Hui-Qiang Ding🇨🇳 · Shi-Yao Wang🇨🇳
We study the influence of the in-medium mass difference between boson and antiboson on their spectra. The in-medium mass difference may lead to a difference between the transverse momentum spectra of boson and antiboson. This effect increases with the increasing in-medium mass difference between boson and antiboson. The difference between the transverse momentum spectra of boson and antiboson increases with the increasing expanding velocity of the source and decreases with the increasing transverse momentum in large transverse mass region (mT > 1:6 GeV). The interactions between the hadron and the medium may increase with the increasing temperature of the medium and the higher freeze-out temperature may lead to a larger mass difference between boson and antiboson, and may give rise to a larger difference between the transverse momentum spectra of boson and antiboson for higher freeze-out temperature.
Comments:
11 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2103.13007 [pdf]
IJMPE(2021)·3 citations
03
[Submitted on 24 Mar 2021]
Is the pole content of each single-energy, single-channel partial wave analysis inherently model dependent?
Alfred Svarc🇭🇷
Unfortunately, yes, it is. In ref.[1] it has been shown that without fixing the reaction-amplitude phase, many combinations of partial waves at neighboring energies in single-energy, single-channel partial wave analysis reproduce experimental data identically, but are discontinuous and disconnected. To obtain the continuous solution, the phase has to be fixed to some continuous value. In the same reference it has also been shown that the change of angular part of reaction-amplitude phase mixes partial waves, so the pole structure of any single-energy single-channel partial wave analysis depends on the chosen phase. As in any single-channel analysis the overall reaction-amplitude phase cannot be determined because of continuum ambiguity, it is in principle free and has to be taken from some coupled-channel model. Because of the difference in the angular part of the phase, choosing different phases results in the change of the pole content of the obtained solution. Therefore, single-energy single-channel partial wave analysis is inherently model dependent, and the number of poles it contains strongly depends on the choice of the phase. In that reference these facts have been illustrated on the pseudo-scalar meson production toy model. This truth is now for the measured observables demonstrated on the realistic model of ref. [2] which combines amplitude and partial wave analysis in one self-consistent scheme for the the world collection of {\eta}-photoproduction data, and fixes the phase to BG2014-2 solution [3]. We show that the pole structure of the solution whose phase is very close to the BG2014-2 theoretical ED phase is very similar to the pole structure of BG2014-2 solution, but the agreement with the data is not ideal. However, improving the agreement with the data requires the departure from BG2014-2 ED phase, and this spoils analytic structure of the obtained solution.
Comments:
15 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.13052 [pdf]
PRC(2021)·3 citations
04
[Submitted on 24 Mar 2021]
Influence of the treatment of initialization and mean-field potential on the neutron to proton yield ratios
Junping Yang🇨🇳 · Yingxun Zhang🇨🇳 · Ning Wang🇨🇳 · Zhuxia Li🇨🇳
In this work, we firstly investigate how to reproduce and how well one can reproduce the Woods-Saxon density distribution of initial nuclei in the framework of the improved quantum molecular dynamics model. Then, we propose a new treatment for the initialization of nuclei which is correlated with the nucleonic mean-field potential by using the same potential energy density functional. In the mean field potential, the three-body force term is accurately calculated. Based on the new version of the model, the influences of precise calculations of the three-body force term, the slope of symmetry energy, the neutron-proton effective mass splitting, and the width of the wave packet on heavy ion collision observables, such as the neutron to proton yield ratios for emitted free nucleons [ $R (n / p)$ ] and for coalescence invariant nucleons [ $R_{c i} (n / p)$ ] for $^{124}$ Sn+ $^{112}$ Sn at the beam energy of 200 MeV per nucleon, are discussed. Our calculations show that the spectra of neutron to proton yield ratios [ $R (n / p)$ ] can be used to probe the slope of symmetry energy ( $L$ ) and the neutron-proton effective mass splitting. In detail, the $R (n / p)$ in the low kinetic energy region can be used to probe the slope of symmetry energy ( $L$ ). With a given $L$ , the inclination of $R (n / p)$ to kinetic energy ( $E_{k}$ ) can be used to probe the effective mass splitting. In the case where the neutron-proton effective mass splitting is fixed, $R (n / p)$ at high kinetic energy can also be used to learn the symmetry energy at suprasaturation density.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.13132 [pdf]
PRC(2021)·21 citations
05
[Submitted on 24 Mar 2021]
Updated systematics of intermediate-energy single-nucleon removal cross sections
J.A. Tostevin🇬🇧 · A. Gade🇺🇸
The body of experimental measurements of intermediate-energy reactions that remove a single nucleon from a secondary beam of neutron- or proton-rich nuclei continues to grow. These data have been analysed consistently using an approximate, eikonal-model treatment of the reaction dynamics combined with appropriate shell-model descriptions of the projectile initial state, the bound final states spectrum of the reaction residue and single-particle removal strengths computed from their wave-function overlaps. The systematics of the ratio $R_{s}$ of the measured inclusive cross-section to all bound final states and the calculated cross-section to bound shell-model states -- in different regions of the nuclear chart and involving both very weakly-bound and strongly-bound valence nucleons -- is important in relating the empirically deduced orbital occupancies to those from the best available shell-model predictions. Importantly, several new higher-energy measurements, for which the sudden-approximation aspect of the dynamical description is placed on an even stronger footing, now supplement the previously-analysed measurements. These additional data sets are discussed. Their $R_{s}$ values are shown to conform to and reinforce the earlier-observed systematics, with no indication that the approximately linear reduction in $R_{s}$ with increasing nucleon separation energy is a consequence of a breakdown of the sudden approximation.
Comments:
8 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.13133 [pdf]
PRC(2021)·72 citations
06
[Submitted on 24 Mar 2021]
$g$ -factor and static quadrupole moment of $^{135}$ Pr, $^{105}$ Pd, and $^{187}$ Au in wobbling motion
C. Broocks🇩🇪 · Q. B. Chen🇩🇪 · N. Kaiser🇩🇪 · Ulf-G. Meißner🇩🇪
The $g$ -factor and static quadrupole moment of the nuclides $^{135}$ Pr, $^{105}$ Pd, and $^{187}$ Au in the wobbling motion are investigated in the particle-rotor model as functions of the total spin $I$ . The $g$ -factor of $^{105} Pd$ increases with increasing $I$ , due to the negative gyromagnetic ratio of a neutron valence-neutron. This behavior is in contrast to the decreasing $g$ -factor of the other two nuclides, $^{135}$ Pr and $^{187}$ Au, which feature a valence-proton. The static quadrupole moment $Q$ depends on all three expectation values of the total angular momentum. It is smaller in the yrast band than in the wobbling band for the transverse wobblers $^{135}$ Pr and $^{105}$ Pd, while larger for the longitudinal wobbler $^{187}$ Au.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.13174 [pdf]
EPJA(2021)·16 citations
07
[Submitted on 24 Mar 2021]
Partial dynamical symmetry from energy density functionals
K. Nomura🇭🇷 · N. Gavrielov🇮🇱 · A. Leviatan🇮🇱
We show that the notion of partial dynamical symmetry is robust and founded on a microscopic many-body theory of nuclei. Based on the universal energy density functional framework, a general quantal boson Hamiltonian is derived and shown to have essentially the same spectroscopic character as that predicted by the partial SU(3) symmetry. The principal conclusion holds in two representative classes of energy density functionals: nonrelativistic and relativistic. The analysis is illustrated in application to the axially-deformed nucleus $^{168}$ Er.
Comments:
7 pages, 3 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.13216 [pdf]
PRC(2021)·5 citations
08
[Submitted on 24 Mar 2021]
Effects of Pauli blocking and in-medium nucleon-nucleon cross sections on the stopping power at low-intermediate energy heavy ion collisions
Xiang Chen🇨🇳 · Yingxun Zhang🇨🇳 · Zhuxia Li🇨🇳
Three typical algorithms of Pauli blocking in the quantum molecular dynamics type models are investigated in the nuclear matter, the nucleus and the heavy ion collisions. The calculations in nuclear matter show that the blocking ratios obtained with the three algorithms are underestimated 13-25\% compared to the analytical values of blocking ratios. For the finite nucleus, the spurious collisions occur around the surface of the nucleus owing to the defects of Pauli blocking algorithms. In the simulations of heavy ion collisions, the uncertainty of stopping power from different Pauli blocking algorithms is less than 5\%. Furthermore, the in-medium effects of nucleon-nucleon ( $N N$ ) cross sections on the nuclear stopping power are discussed. Our results show that the transport models calculations with free $N N$ cross sections result in the stopping power decreasing with the beam energy at the beam energy less than 300 MeV/u. To increase or decrease the values of stopping power, an enhanced or suppressed model dependent in-medium $N N$ cross section is required.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2103.13218 [pdf]
0 citations
09
[Submitted on 24 Mar 2021]
Efficient emulator for solving three-nucleon continuum Faddeev equations with chiral three-nucleon force comprising any number of contact terms
H. Witała🇵🇱 · J. Golak🇵🇱 · R. Skibiński🇵🇱
We demonstrate a computational scheme which drastically decreases the required time to get theoretical predictions based on chiral two- and three-nucleon forces for observables in three-nucleon continuum. For a three-nucleon force containing N short-range terms all workload is reduced to solving N+1 Faddeev-type integral equations. That done, computation of observables for any combination of strengths of the contact terms is done in a flash. We demonstrate on example of the elastic nucleon-deuteron scattering observables the high precision of the proposed emulator and its capability to reproduce exact results.
Comments:
13 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:2102.13408
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.13237 [pdf]
EPJA(2021)·13 citations
10
[Submitted on 24 Mar 2021]
Pions and Contacts at N4LO: Some details on the chiral nuclear force
E. F. Batista🇧🇷 · S. Szpigel.🇧🇷 · V. S. Timoteo🇧🇷
In this work we have performed a detailed study of chiral nuclear forces at N4LO approximation applied to selected channels of the neutron-proton ( $n p$ ) scattering. The idea is to analyse the different contributions to the nucleon-nucleon ( $N N$ ) potential by separating the part coming from the exchange of pions and the one coming from the contact interactions. We consider two state-of-the-art chiral interactions at N4LO which are constructed using different regularization procedures: the non-local Idaho-Salamanca force and the semi-local interaction from the Bochum group. In order to compare the two types of regularization we consider both interactions with a 500 MeV cutoff and to analyse the cutoff dependence we select the Bochum potential with three different cutoff values: 500, 450 and 400 MeV. Our results show that the balance between pion exchanges and contact interactions depends strongly on the regularization procedure. The non-local angle-independent regularization of both components of the interaction implemented in the Idaho-Salamanca potential make the contact terms to be present at large distances while the local regularization of the pion exchanges in the Bochum potential restricts the contact interactions to small distances. Also, the value of the cutoff affects the strength of the potential but the interplay between pion exchanges and contact terms remains qualitatively the same.
Comments:
17 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.13352 [pdf]
Annals Phys.(2021)·1 citation
11
[Submitted on 24 Mar 2021]
On-shell transition of SRG and nuclear systems
E. Ruiz Arriola🇪🇸 · S. Szpigel🇧🇷 · V. S. Timoteo🇧🇷
We make variational estimates for the binding energies of $^{2} H,^{3} H,^{4} H e,^{16} O,^{40} C a$ , showing their running with the Similarity Renormalization Group (SRG) cutoff towards the infrared region and show the generalized Tjon lines that emerge from the calculations. We infer the SRG evolution of the three-body contributions for the $^{3} H$ and $^{4} H e$ binding energies by computing the two-body contributions with a variational approach assuming that four-body forces are negligible. At any given SRG cutoff, the three-body contributions may then be inferred as being the experimental value minus the two-body contributions. The off-shell / on-shell transition at a critical SRG cutoff $λ_{c}$ drives the behavior of all binding energies and this scale is the turning point of the generalized Tjon lines. Also, at $λ_{c}$ the ratios between three-body and two-body contributions to the binding energies, $B_{λ_{c}} (3) / B_{λ_{c}} (2)$ , are the same in both $^{3} H$ and $^{4} H e$ systems and equal to $1/4$ , so that $B_{λ_{c}} (2) = 4 B_{λ_{c}} (3)$ . All calculations are carried out with the Idaho-Salamanca N3LO potential, which is evolved with the SRG up to the infrared fixed point ( $λ \to 0$ ) in all S, P, D, F and G partial-wave channels in order to compute the variational binding energies at several SRG cutoff scales.
Comments:
Annals of Physics, in press (11 pages, 8 figures)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.13363 [pdf]
Annals Phys.(2021)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE