Neutron Skin Thickness Research Articles

New quantification of symmetry energy from neutron skin thicknesses of 48Ca and 208Pb

New quantification of symmetry energy from neutron skin thicknesses of 48Ca and 208Pb

How do mirror charge radii constrain density dependence of the symmetry energy?

It has recently been suggested that differences in the charge radii of mirror nuclei (ΔRchmirr) are strongly correlated with the neutron-skin thickness (Rskin) of neutron-rich nuclei and with the slope of the symmetry energy (L). To test this assumption, we present ab initio calculations of Rskin in 48Ca and 208Pb, ΔRchmirr in 36Ca−36S, 38Ca−38Ar, 41Sc−41Ca, 48Ni−48Ca, 52Ni−52Cr, and 54Ni−54Fe mirror pairs, and L. Employing the recently developed 34 chiral interaction samples, identified by the history matching approach, we conduct rigorous statistical analysis of correlations among ΔRchmirr, Rskin and L, accounting for quantified uncertainties from low-energy constants of chiral interaction, chiral effective field theory truncation and many-body method approximation. The ab initio results reveal an appreciable ΔRchmirr−L correlation in fp-shell mirror pairs. However, contrary to previous studies, the present calculation finds that the studied sd-shell mirror pairs do not exhibit any ΔRchmirr−L correlation.

The Neutron Skin-Thickness of 208Pb Determined by Electron and Proton Scattering

Abstract Electron as well as proton elastic scattering is not able to determine the point proton and point neutron densities, $\rho _\tau (r), (\tau =p,n)$, separately. If both scatterings are analyzed consistently, those densities would be determined uniquely, since the two densities are observed by different combinations from each other. Previous experiments have not provided $\rho _\tau (r)$ uniquely, but the values of the mean square radii of $\rho _p(r)$, $\langle \, r^2\, \rangle _p$, and of $\rho _n(r)$, $\langle \, r^2\, \rangle _n$, are shown to be determined consistently through the fourth moment of the observed charge density, $\langle \, r^4\, \rangle _c$, in 208Pb. The previous analyses of $(\gamma , \pi ^0)$ and $\bar{p}$-nucleus obtained a similar value of $\langle \, r^2\, \rangle _n$, but they do not yield the experimental value of $\langle \, r^4\, \rangle _c$ observed in electron scattering.

Bayesian inference of neutron-skin thickness and neutron-star observables based on effective nuclear interactions

Bayesian inference of neutron-skin thickness and neutron-star observables based on effective nuclear interactions

Relativistic description of dense matter equation of state and neutron star observables constrained by recent astrophysical observations

In the present work, we investigate the bulk properties of nuclear matter and neutron stars with the newly proposed relativistic interaction NL-RS which provides an opportunity to readjust the coupling constants keeping in view the properties of finite nuclei, nuclear matter, PREX-II results for neutron skin thickness in 208Pb and astrophysical observations. The NL-RS model interaction has been proposed by fitting the ground state properties (binding energies and charge radii) of finite nuclei, bulk nuclear matter properties, and PREX-II results for neutron skin thickness of 208Pb. The relativistic interaction has been generated by including nonlinear self-interactions of σ and ω μ -mesons and mixed interactions of ω μ , and ρ μ -meson up to the quartic order. The proposed interaction harmonizes with the finite nuclei, bulk nuclear matter, and neutron star properties. A covariance analysis is performed to assess the statistical uncertainties on the model parameters and nuclear observables of interest along with correlations amongst them. The equation of state (EoS) composed of nucleons and leptons in β-equilibrium is computed with the proposed parameter set and used to study the neutron star structure. The maximum mass of the neutron star by employing the EoS computed with the NL-RS parameter set is 2.04 ± 0.03M ⊙ and the radius of a canonical mass neutron star (R 1.4) comes out to be equal to 13.06 ± 0.16 Km. The value of dimensionless tidal deformability, for canonical mass, is 602.23 ± 33.13 which satisfies the constraints of waveform models analysis of GW170817 within 90% confidence level.

Measurement of nuclear interaction cross sections towards neutron-skin thickness determination

The accuracy of reaction theories used to extract properties of exotic nuclei from scattering experiments is often unknown or not quantified, but of utmost importance when, e.g., constraining the equation of state of asymmetric nuclear matter from observables as the neutron-skin thickness. In order to test the Glauber multiple-scattering model, the total interaction cross section of ▪ on carbon targets was measured at initial beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The measurements were performed during the first experiment of the newly constructed R3B (Reaction with Relativistic Radioactive Beams) experiment after the start of FAIR Phase-0 at the GSI/FAIR facility with beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The combination of the large-acceptance dipole magnet GLAD and a newly designed and highly efficient Time-of-Flight detector enabled a precise transmission measurement with several target thicknesses for each initial beam energy with an experimental uncertainty of ±0.4%. A comparison with the Glauber model revealed a discrepancy of around 3.1% at higher beam energies, which will serve as a crucial baseline for the model-dependent uncertainty in future fragmentation experiments.

Structural and decay properties of even–even trans-lead nuclei

A systematic study of the ground-state properties of even–even Po, Rn, Ra and Th isotopes is conducted using the self-consistent Skyrme-Hartree–Fock–Bogoliubov (HFB) theory. Different Skyrme interactions are employed in the study. The bulk properties such as binding energy, two-neutron separation energies, two-proton separation energies and neutron skin thickness are investigated. The obtained results from the Skyrme-HFB formalism are compared with the calculated results from the Finite Range Droplet Model (FRDM) and the available experimental data. Our theoretical values were found to be consistent with their counterparts. In addition, the density-dependent cluster model is utilized to estimate [Formula: see text]-decay half-lives. A good agreement is achieved between the calculated results and the recent experimental data.

A possible probe to neutron-skin thickness by fragment parallel momentum distribution in projectile fragmentation reactions

A possible probe to neutron-skin thickness by fragment parallel momentum distribution in projectile fragmentation reactions

Linkage among the neutron-skin thickness of 208Pb and nuclear symmetry energy using heavy particle radioactivity

The nuclear symmetry energy (NSE) is a linchpin in deciphering the behavior of matter in a wider domain extending from the characteristics of exotic nuclei to those of neutron stars in the cosmos. Therefore, it is crucial to utilize potential probes to constrain the NSE and its slope parameter L(ρ 0). In this work, we put forth the heavy particle radioactivity (HPR) as a probable bridge among the slope of NSE (L(ρ 0)) and neutron-skin thickness of 208Pb (R skin 208), which serves to put constrain on the L(ρ 0) value. The NSE and its slope parameter are determined from the single nucleon potential of asymmetric nuclear matter exploiting the analytical relationship between these quantities. The isovector/symmetry potential component of the single nucleon potential is derived through HPR for varying R skin 208 by employing the heavy particle/cluster densities and core densities from the relativistic mean field model in conjunction with M3Y nucleon–nucleon interaction. It facilitates in constraining the L(ρ 0) value and neutron skin of finite nuclei using HPR as a linkage, where heavy cluster and core densities of standard Fermi form are considered. The constrained value of L(ρ o ) is 45 ± 8 MeV, which aligns with other estimations derived from nuclear mass measurements, dipole polarizability measurements, and astrophysical data.

A systematic study of the ground state properties of gold nuclei near the neutron drip line using HFB formalism

In this theoretical work, the ground state properties like binding energy per nucleon, two-neutron separation energy, two-neutron shell gap, neutron-pairing gap, neutron rms radii, proton rms radii, charge radii, neutron skin thickness and nucleon density distributions of odd-even and odd-odd gold isotopes (A165−265u) were systematically studied. Computations were performed for a wide mass range of gold nuclei, spanned from the proton-rich side to the neutron-rich side, following the Hartree-Fock-Bogoliubov theory. Based on this approach, the nuclear structure of gold isotopes lying up to the exotic neutron rich region where the experimental data are not available, was also investigated. Calculations, taking into account the UNEDF0 Skyrme effective interaction, reproduce the available experimental data and results of other nuclear model based estimations, such as the Relativistic-Continuum-Hartree-Bogoliubov theory and the Finite Range Droplet Models, reasonably well.

Electric dipole polarizability of magic nuclei

The correlations between the electric dipole polarizability and neutron skin thickness are studied by the magic nuclei 40,48Ca, 68,78Ni, 132Sn, and 208Pb. The strength distribution of the E1 transitions is calculated within the random phase approximation model based on the Skyrme nuclear energy density functional. A comparison with the experimental data has allowed us to constrain the value of the nuclear symmetry energy J = 30–37 MeV.

Implications on Skyrme equations of state from neutron skin measurements

Abstract The recent measurements on neutron skins via parity violation in electron scattering have extracted an abnormal thick neutron skin for $^{208}$Pb, which has significant consequences in nuclear equation of state (EoS) and neutron star observations. This work performs optimizations of extended Skyrme forces in a consistent manner by including neutron skin thicknesses from PREX-II and CREX experiments
and investigates nuclear EoS and neutron stars in the GW170817 event. By varying the fitting weights of neutron skins, several new Skyrme parameterizations are obtained. Our results show the competition in the fitting procedure to simultaneously describe neutron skins, other properties of finite nuclei and neutron star observations. The prospects in resolving the neutron skin issues are also discussed.

Determining the neutron skin thickness by relativistic semi-isobaric collisions

Determining the neutron skin thickness by relativistic semi-isobaric collisions

A study of trends of neutron skin thickness and proton radii of mirror nuclei within the framework of covariant density functional theory

The neutron skin of atomic nuclei impacts the structure of neutron-rich nuclei, but its accurate measurement is quite challenging. We present predictions for neutron skins and proton radii for light to medium mass nuclei by employing Covariant Density Functional Theory (CDFT) based on density-dependent meson-exchange interaction. Using our microscopic predictions, we find a linear correlation between the neutron skin and the isospin asymmetry. The calculations are also extended to find a linear relationship between proton and neutron radii of mirror nuclei. Using the charge symmetry property of nuclear forces, a correlation between the neutron skin of neutron-rich nuclei and difference between the proton radii of the corresponding mirror pair has also been investigated. The inclusion of ISB term is found to affect the mirror difference charge radii of [Formula: see text]Ca-[Formula: see text]Ni mirror pair.

Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

Neutron skin of 27Al with Skyrme and Korea-IBS-Daegu-SKKU density functionals

Recent measurement of the parity-violating (PV) asymmetry in the elastic electron scattering on [Formula: see text]Al target evokes the interest in the distribution of the neutron in the nucleus. In this work, we calculate the neutron skin thickness ([Formula: see text]) of [Formula: see text]Al with nonrelativistic nuclear structure models. We focus on the role of the effective mass, symmetry energy and pairing force. Models are selected to have effective masses in the range (0.58–1.05) M where M is the nucleon mass in free space, and stiffness of the symmetry energy is varied by choosing the slope of the symmetry energy in the range 9.4–100.5[Formula: see text]MeV. Effect of pairing force is investigated by calculating nuclear properties with and without pairing. With constant force pairing, we obtain [Formula: see text]–0.013[Formula: see text]fm. The result is independent of the effective mass and symmetry energy. However, [Formula: see text] is negative when the pairing force is switched off, so the pairing force plays an essential role to make [Formula: see text] positive and constrained in a narrow range. We also calculate the PV asymmetry ([Formula: see text]) in the elastic electron-[Formula: see text]Al scattering in the Born approximation at the kinematics of the Qweak experiment. We obtain a very narrow-ranged result [Formula: see text]. The result is consistent with the experiment and insensitive to the effective mass and symmetry energy.

Hybrid stars and the stiffness of the nuclear equation of state in light of the HESS J1731-347 remnant

The recent observation of the extremely compact neutron star in the HESS J1731-347 remnant has challenged our understanding concerning the nature of dense nuclear matter. In particular, the low radius of the aforementioned compact object favors soft nuclear equations of state. However, the neutron skin thickness of 208Pb extracted from the long-awaited PREX-II experiment favors stiff equations of state which may be associated with larger radii for low mass stellar configurations. In this contribution we present our recent work on the possible reconciliation of the HESS J1731-347 observation in the framework of hybrid stars, under the assumption of a stiff low-density phase which may be favored by the PREX-II results. In addition, we examine the compatibility of the resulting hybrid models with recent constraints based on the observation of PSR J0030+0451, PSR J0952-0607 and GW190814.

Sensitivity of one-neutron knockout observables of loosely- to more deeply-bound nuclei

For the last few decades, one-nucleon knockout reactions on light composite targets—9Be or 12C—have been extensively used to study the single-particle (s.p.) structure of nuclei far from stability. To determine which information can be accurately inferred from knockout cross sections, we conduct a sensitivity analysis of these observables considering various s.p. descriptions within the usual eikonal description of the reaction. This work shows that total one-neutron knockout cross sections are not sensitive to the short-range part of the s.p. wave function. Rather, they scale with the mean square radius of the overlap function. Using a perturbative expression of the cross section, we can easily explain our numerical predictions analytically. This analysis suggests that (i) spectroscopic factors extracted from knockout data suffer from sizeable model uncertainties associated with the choice of s.p. wave functions and (ii) knockout reactions constitute an excellent probe of the radius of the nucleus and therefore offer an alternative technique to infer the neutron-skin thickness of exotic nuclei.

Tensor and isovector–isoscalar terms of relativistic mean field model: Impacts on neutron-skin thickness, charge radius, and nuclear matter

The origin of the neutron skin thickness, measured by the CREX and PREX collaborations as thin for 40Ca and thick for 28Pb, remains a mystery. We investigate the effects of tensor and nonlinear isovector–isoscalar terms in a relativistic mean-field model (RMF) on the properties of finite nuclei and nuclear matter. Tensor couplings are crucial for better quality binding energies of finite nuclei and charge radii for relatively heavy nuclei. However, for light nuclei, the tensor terms cannot improve the compatibility of charge radius predictions by the RMF model with experimental data. We find that parameter sets with a larger nonlinear isovector–isoscalar parameter, particularly η2ρ = 0.028, agree better with experimental data for Δrnp across light, medium, and heavy isotope chains. Using PT28, we calculate Δrnp for 208Pb as 0.214 fm, J as 33.078, and L as 58.426. Δrnp for 208Pb obtained using PT28 is consistent with the PREX-II data. Moreover, the corresponding values of J and L agree with the low L constraints. Meanwhile, the canonical mass radius predicted by PT28 aligns with the mass and radius data from the NICER collaboration. The combination of tensor and nonlinear isovector–isoscalar couplings in the RMF model provides accurate predictions for finite nuclei binding energies and relatively heavy nuclei charge radii, resulting in relatively thick Δrnp values for 208Pb without substantial L values.

Alpha clustering in 41, 45, 49Ca* nuclei formed in neutron induced reactions

The light neutron-rich nuclei play a vital role in nucleosynthesis process and the extent of alpha (α) clustering significantly influence the astrophysical rates. Thus, it is significant to explore the α clustering in these nuclei and in the present work, we have studied the α clustering in 41,45,49Ca* nuclei formed in neutron induced reactions within the dynamical cluster decay model (DCM). The results present that with progression towards neutron-rich 45Ca* and 49Ca* nuclei, there is a significant decrease in the α-cluster preformation factor P0. The inclusion of relativistic mean field theory (RMFT) based microscopic temperature-dependent binding energies (T.B.E.) within DCM, give relatively enhanced α-cluster preformation factor for 41,45,49Ca* nuclei compared to the case of macroscopic T.B.E. based upon Davidson mass formula. The cross-section associated with α-cluster emission depicts strong isospin dependence and falls off significantly with increasing neutron number of Ca* nuclei. Further, for the first time, we inculcate the microscopic nuclear potential constructed via folding the standard Fermi form fitted RMFT cluster densities and M3Y nucleon-nucleon interaction within the DCM. The neutron skin thickness of the Ar cluster, complementary to α-cluster, is varied and its effect upon the nuclear interaction potential and α-cluster preformation factor is analysed. The results present that with growing neutron skin of Ar cluster, the α-cluster preformation factor decreases. It explores a strong correlation among the neutron skin thickness and α-cluster preformation factor in light mass 41,45,49Ca* nuclear systems.