Nuclear Theory·nucl-th

Wednesday·June 2, 2021

12 papers—9 primary·3 cross-listed

01
[Submitted on 1 Jun 2021]
Isotopic analysis of 295 MeV proton scattering off $^{204, 206, 208}$ Pb for improvement of neutron densities and radii
Yoshiko Kanada-En'yo
A new method of reaction analysis for proton elastic scattering is proposed, combining systematic analyses of nuclear structure and reactions in a series of isotopes. This method is applied to $^{204}$ Pb $(p, p)$ , $^{206}$ Pb $(p, p)$ , and $^{208}$ Pb $(p, p)$ at $E_{p} = 295$ MeV to obtain improved neutron densities and radii from experimental cross section data. The reaction calculation is performed according to the relativistic impulse approximation using the modified Murdock and Horowitz model with density-dependent effective $N N$ interaction. Analysis of Pb isotopes is performed using theoretical densities given by the relativistic Hartree-Bogoliubov and nonrelativistic Skyrme Hartree-Fock-Bogoliubov calculations and the experimental density extracted from the $(p, p)$ data at 295 MeV. The isotopic ratios ( $R (σ)$ ) of the $^{A}$ Pb $(p, p)$ -to- $^{206}$ Pb $(p, p)$ cross sections are analyzed in connection with the isotopic differences ( $D (ρ_{n})$ and $D (r_{n})$ ) in neutron densities $(ρ_{n} (r))$ and radii $(r_{n})$ between $^{A}$ Pb and $^{208}$ Pb. A hole-model analysis is performed, assuming $^{204}$ Pb and $^{206}$ Pb as a $^{208}$ Pb core and neutron holes to clarify the one-to-one correspondence between isotopic structure properties such as $D (ρ_{n})$ and $D (r_{n})$ and the isotopic cross-section ratio. By fitting $R (σ)$ , the values of $D (ρ_{n})$ and $D (r_{n})$ are extracted from the experimental $(p, p)$ cross section data with less uncertainty of the structure and reaction models. The isotopic neutron radius difference between $^{206}$ Pb and $^{208}$ Pb was obtained as $D (r_{n}) = - 0.012$ fm with an acceptable range of $D (r_{n}) = - 0.03 \sim - 0.006$ fm.
Comments:
20 pages, 24 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00151 [pdf]
3 citations
02
[Submitted on 1 Jun 2021]
Systematic calculations of reactions with exotic and stable nuclei to establish a unified theoretical approach
M. A. G. Alvarez · M. Rodriguez-Gallardo · J. P. Fernandez-Garcia · J. Casal · J. A. Lay
We report on systematical optical model (OM) and continuum discretized coupled channel (CDCC) calculations applied to describe the elastic scattering angular distributions of exotic and stable nuclei projectiles on heavy targets. Our optical potential (OP) is composed of the nuclear microscopic double folding São Paulo potential (SPP), derived from the nonlocal nature of the interaction, and the Coulomb dipole polarization (CDP) potential, derived from the semiclassical theory of Coulomb excitation. The OP is compared to the trivial equivalent local potential (TELP), extracted from CDCC calculations. The OM and CDCC predictions corroborate each other and account for important differences in the nuclei reaction mechanisms, which are directly related to their structural properties. Thus, OM and CDCC establish a common basis for analyzing or even predicting exotic and stable nuclei reactions.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00292 [pdf]
PRC(2021)·11 citations
03
[Submitted on 1 Jun 2021]
Strong magnetic fields: neutron stars with an extended inner crust
Helena Pais · Bruno Bertolino · Jianjun Fang · Xiaopeng Wang · Constança Providência
Using relativistic mean-field models, the formation of clusterized matter, as the one expected to exist in the inner crust of neutron stars, is determined under the effect of strong magnetic fields. As already predicted from a calculation of the unstable modes resulting from density fluctuations at subsaturation densities, we confirm in the present work that for magnetic field intensities of the order of $\approx 5 \times 1 0^{16}$ G to $5 \times 1 0^{17}$ G, pasta phases may occur for densities well above the zero-field crust-core transition density. This confirms that the extension of the crust may be larger than expected. It is also verified that the equilibrium structure of the clusterized matter is very sensitive to the intensity of the magnetic fields. As a result, the decay of the magnetic field may give rise to internal stresses which may result on the yield and fracture of the inner crust lattice.
Comments:
9 pages, 4 figures, accepted for publication in the EPJ A Topical Issue "The QCD Phase Diagram in Strong Magnetic Fields"
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2106.00347 [pdf]
EPJA(2021)·10 citations
04
[Submitted on 1 Jun 2021]
Medium effects in antikaon-induced $Ξ^{-}$ hyperon production on nuclei near threshold
E. Ya. Paryev🇷🇺
We study the antikaon-induced inclusive cascade $Ξ^{-}$ hyperon production from $^{12}$ C and $^{184}$ W target nuclei near threshold within a nuclear spectral function approach. The approach describes incoherent direct $Ξ^{-}$ hyperon production in elementary $K^{-} p \to K^{+} Ξ^{-}$ and $K^{-} n \to K^{0} Ξ^{-}$ processes as well as takes into account the influence of the scalar nuclear $K^{-}$ , $K^{+}$ , $K^{0}$ , $Ξ^{-}$ and their Coulomb potentials on these processes. We calculate the absolute differential and total cross sections for the production of $Ξ^{-}$ hyperons off these nuclei at laboratory angles $\leq$ 45 $^{\circ}$ by $K^{-}$ mesons with momenta of 1.0 and 1.3 GeV/c, which are close to the threshold momentum (1.05 GeV/c) for $Ξ^{-}$ hyperon production on the free target nucleon at rest. We also calculate the momentum dependence of the transparency ratio for the $^{184}$ W/ $^{12}$ C combination for $Ξ^{-}$ hyperons at these $K^{-}$ beam momenta. We show that the $Ξ^{-}$ differential and total (absolute and relative) production cross sections at the considered initial momenta reveal a distinct sensitivity to the variations in the scalar $Ξ^{-}$ nuclear potential at saturation density $ρ_{0}$ , studied in the paper, in the low-momentum region of 0.1--0.6 GeV/c. We also demonstrate that for the subthreshold $K^{-}$ meson momentum of 1.0 GeV/c there is a strong sensitivity of the transparency ratio for $Ξ^{-}$ hyperons to the considered changes in the $Ξ^{-}$ nuclear potential at all outgoing $Ξ^{-}$ momenta as well. Therefore, the measurement of these absolute and relative observables in a dedicated experiment at the J-PARC will provide valuable information on the $Ξ^{-}$ in-medium properties, which will be complementary to that deduced from the study of the inclusive ( $K^{-}$ , $K^{+}$ ) reactions at incident momenta of 1.6--1.8 GeV/c in the $Ξ^{-}$ bound and quasi-free regions.
Comments:
31 pages. arXiv admin note: text overlap with arXiv:2102.00789
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2106.00353 [pdf]
NPA(2021)·3 citations
05
[Submitted on 1 Jun 2021]
Symmetry potentials and in-medium nucleon-nucleon cross sections within the Nambu-Jona-Lasinio model in relativistic impulse approximation
Si-Na Wei🇨🇳 · Rong-Yao Yang🇨🇳 · Jing Ye🇨🇳 · Niu Li🇨🇳 · Wei-Zhou Jiang🇨🇳
In the relativistic impulse approximation (RIA), we study symmetry potentials and in-medium nucleon-nucleon (NN) cross sections with the Nambu-Jona-Lasinio (NJL) model that features chiral symmetry. The chiral symmetry that plays a fundamental role in the nonperturbative physics in the strong interaction is anticipated to add restrictive effects on the symmetry potentials and in-medium NN cross sections. For comparison, we also perform the study with the usual relativistic mean-field (RMF) model. The numerical results with the NJL and RMF models are similar at saturation density and below, since a priori fit was made to saturation properties. With the increase of nuclear density, the chiral symmetry starts to be restored partially in the NJL model, resulting in the explicit fall of the scalar density. In a large energy span, the symmetry potential acquires a significant rise for the partial restoration of the chiral symmetry, compared to the one with the RMF model. It is found that the in-medium NN cross sections in the RIA with the NJL and RMF models both increase with the density in the energy region interested in this study, whereas those with the NJL model increase sharply as long as a clear chiral symmetry restoration takes place. The different tendency of observables in density can be transmitted to the different energy dependence in the RIA. The NJL model is shown to have characteristic energy-dependent symmetry potentials and NN cross sections beyond saturation point, apart from the RMF models.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00429 [pdf]
PRC(2021)·5 citations
06
[Submitted on 1 Jun 2021]
Wave-packet continuum discretisation for nucleon-nucleon scattering predictions
Sean B. S. Miller🇸🇪 · Andreas Ekström🇸🇪 · Christian Forssén🇸🇪
In this paper we analyse the efficiency, precision, and accuracy of computing elastic nucleon-nucleon (NN) scattering amplitudes with the wave-packet continuum discretisation method (WPCD). This method provides approximate scattering solutions at multiple scattering energies simultaneously. We therefore utilise a graphics processing unit (GPU) to explore the benefits of this inherent parallelism. From a theoretical perspective, the WPCD method promises a speedup compared to a standard matrix-inversion method. We use the chiral NNLO $_{opt}$ interaction to demonstrate that WPCD enables efficient computation of NN scattering amplitudes provided one can tolerate an averaged method error of $1 - 5$ mb in the total cross section at scattering energies $0 - 350$ MeV in the laboratory frame of reference. Considering only scattering energies $\sim 40 - 350$ MeV, we find a smaller method error of $≲ 1 - 2$ mb. By increasing the number of wave-packets we can further reduce the overall method error. However, the parallel leverage of the WPCD method will be offset by the increased size of the resulting discretisation mesh. In practice, a GPU-implementation is mainly advantageous for matrices that fit in the fast on-chip shared memory. We find that WPCD is a promising method for computationally efficient, statistical analyses of nuclear interactions from effective field theory, where we can utilise Bayesian inference methods to incorporate relevant uncertainties.
Comments:
33 pages, 9 figures, v2 corresponds to published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00454 [pdf]
J.Phys.G(2022)·10 citations
07
[Submitted on 1 Jun 2021]
Space-average electromagnetic fields and EM anomaly weighted by energy density in heavy-ion collisions
Irfan Siddique🇨🇳 · Xin-Li Sheng🇨🇳 · Qun Wang🇨🇳
We study the space-average electromagnetic (EM) fields weighted by the energy density in the central regions of heavy ion collisions. These average quantities can serve as a barometer for the magnetic-field induced effects such as the magnetic effect, the chiral separation effect and the chiral magnetic wave. Comparing with the magnetic fields at the geometric center of the collision, the space-average fields weighted by the energy density are smaller in the early stage but damp slower in the later stage. The space average of squared fields as well as the EM anomaly $E \cdot B$ weighted by the energy density are also calculated. We give parameterized analytical formula for these average quantities as functions of time by fitting numerical results for collisions in the collision energy range $7.7 - 200$ GeV with different impact parameters.
Comments:
22 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2106.00478 [pdf]
PRC(2021)·22 citations
08
[Submitted on 1 Jun 2021]
New graphical criterion for the selection of complete sets of polarization observables and its application to single-meson photoproduction as well as electroproduction
Y. Wunderlich🇩🇪
This paper combines the graph-theoretical ideas behind Moravcsik's theorem with a completely analytic derivation of discrete phase-ambiguities, recently published by Nakayama. The result is a new graphical procedure for the derivation of certain types of complete sets of observables for an amplitude-extraction problem with $N$ helicity-amplitudes. The procedure is applied to pseudoscalar meson photoproduction ( $N = 4$ amplitudes) and electroproduction ( $N = 6$ amplitudes), yielding complete sets with minimal length of $2 N$ observables. For the case of electroproduction, this is the first time an extensive list of minimal complete sets is published. Furthermore, the generalization of the proposed procedure to processes with a larger number of amplitudes, i.e. $N > 6$ amplitudes, is sketched. The generalized procedure is outlined for the next more complicated example of two-meson photoproduction ( $N = 8$ amplitudes).
Comments:
31 pages, 14 figures, 4 tables; Version 4 has been accepted for publication in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00486 [pdf]
PRC(2021)·8 citations
09
[Submitted on 1 Jun 2021]
Comment on "Sequential Single-Pion Production Explaining the Dibaryon " $d^{*} (2380)$ " Peak"
M. Bashkanov🇬🇧 · H. Clement🇩🇪 · T. Skorodko🇩🇪
In arxiv: 2102.05575 a two-step process $p n \to (pp) π^{-} \to (Δ N) π^{-} \to (d π^{+}) π^{-}$ was calculated by using experimental total cross sections for the single-pion production processes $p n \to pp π^{-} (I = 0)$ and $pp \to d π^{+}$ . As a result the authors obtain a resonance-like structure for the total $p n \to d π^{+} π^{-}$ cross section of about the right size and width of the observed $d^{*} (2380)$ peak at an energy about 40 MeV below the $d^{*} (2380)$ mass. We object both the results of the sequential process calculation and its presentation as an alternative to the dibaryon interpretation.
Comments:
Comment on arXiv:2102.05575
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2106.00494 [pdf]
5 citations

Affiliations

first authorsco-authorsvia INSPIRE