Symmetry energy III: Isovector skins

Danielewicz, Paweł; Singh, Pardeep; Lee, Jenny

doi:10.1016/j.nuclphysa.2016.11.008

Cited by 70 publications

(67 citation statements)

References 95 publications

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“…One therefore finds 0.12 fm<r np <0.28 fm, independent of assumptions concerning S 0 . While this is consistent with most experimental results for 208 Pb, r np =0.159±0.041 (Danielewicz & Lee 2009) (but see Danielewicz et al (2017), who find r np =0.223 ± 0.018 fm), the most recent neutron-skin thickness measurement from the PREX experiment (Abrahamyan et al 2012 fm and thus the mean value is larger than our upper bound. The proposed PREX-II experiment will have an estimated error in r np of about ±0.06 fm Figure 13.…”

Section: Neutron-star Radii and Neutron-skin Thicknessessupporting

confidence: 93%

“…Excluded regions are shown by shading. Left panel: Experimental constraints are from Lattimer & Lim (2013) and Lattimer & Steiner (2014), supplemented by isobaric analog states and isovector skin (IAS+ΔR) results from Danielewicz et al (2017). The thick dashed curve shows the analytic bound from Equation ( physical correlations between the parameters.…”

Section: Applicationsmentioning

confidence: 99%

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Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

Tews¹,

Lattimer²,

Ohnishi³

et al. 2017

ApJ

284

213

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We propose the existence of a lower bound on the energy of pure neutron matter (PNM) on the basis of unitary-gas considerations. We discuss its justification from experimental studies of cold atoms as well as from theoretical studies of neutron matter. We demonstrate that this bound results in limits to the density-dependent symmetry energy, which is the difference between the energies of symmetric nuclear matter and PNM. In particular, this bound leads to a lower limit to the volume symmetry energy parameter S 0 . In addition, for assumed values of S 0 above this minimum, this bound implies both upper and lower limits to the symmetry energy slope parameter L, which describes the lowest-order density dependence of the symmetry energy. A lower bound on neutron-matter incompressibility is also obtained. These bounds are found to be consistent with both recent calculations of the energies of PNM and constraints from nuclear experiments. Our results are significant because several equations of state that are currently used in astrophysical simulations of supernovae and neutron star mergers, as well as in nuclear physics simulations of heavy-ion collisions, have symmetry energy parameters that violate these bounds. Furthermore, below the nuclear saturation density, the bound on neutron-matter energies leads to a lower limit to the density-dependent symmetry energy, which leads to upper limits to the nuclear surface symmetry parameter and the neutron-star crust-core boundary. We also obtain a lower limit to the neutron-skin thicknesses of neutronrich nuclei. Above the nuclear saturation density, the bound on neutron-matter energies also leads to an upper limit to the symmetry energy, with implications for neutron-star cooling via the direct Urca process.

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Section: Neutron-star Radii and Neutron-skin Thicknessessupporting

confidence: 93%

Section: Applicationsmentioning

confidence: 99%

Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

Tews¹,

Lattimer²,

Ohnishi³

et al. 2017

ApJ

284

213

View full text Add to dashboard Cite

show abstract

“…These data are best fit with a neutron-skin thickness of 0.249± 0.023 fm, but larger values also give acceptable reproductions of these data. A recent analysis of (p, n) chargeexchange scattering data also points to the possibility of a larger neutron skin [32]. These skin thicknesses are large compared to recent ab initio calculations of 0.12-0.15 fm from [30].…”

Section: Our P+mentioning

confidence: 92%

Neutron Skin Thickness of Ca48 from a Nonlocal Dispersive Optical-Model Analysis

et al. 2017

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A nonlocal dispersive-optical-model analysis has been carried out for neutrons and protons in 48 Ca. Elastic-scattering angular distributions, total and reaction cross sections, single-particle energies, the neutron and proton numbers, and the charge distribution have been fitted to extract the neutron and proton self-energies both above and below the Fermi energy. From the single-particle propagator resulting from these self-energies, we have determined the charge and neutron matter distributions in 48 Ca. A best fit neutron skin of 0.249±0.023 fm is deduced, but values up to 0.33 fm are still consistent. The energy dependence of the total neutron cross sections is shown to have strong sensitivity to the skin thickness.A fundamental question in nuclear physics is how the constituent neutrons and protons are distributed in the nucleus. In particular, for a nucleus which has a large excess of neutrons over protons, are the extra neutrons distributed evenly over the nuclear volume or is this excess localized in the periphery of the nucleus forming a neutron skin? A quantitative measure is provided by the neutron-skin thickness ∆r np defined as the difference between neutron and proton rms radii, i.e., ∆r np = r n − r p .The nuclear symmetry energy which characterizes the variation of the binding energy as a function of neutronproton asymmetry, opposes the creation of nuclear matter with excesses of either type of nucleon. The extent of the neutron skin is determined by the relative strengths of the symmetry energy between the central near-saturation and peripheral less-dense regions. Therefore ∆r np is a measure of the density dependence of the symmetry energy around saturation [1][2][3][4]. This dependence is very important for determining many nuclear properties, including masses, radii, and the location of the drip lines in the chart of nuclides. Its importance extends to astrophysics for understanding supernovae and neutron stars [5,6], and to heavy-ion reactions [7].Given the importance of the neutron-skin thickness in these various areas of research, a large number of studies (both experimental and theoretical) have been devoted to it [8]. While the value of r p can be determined quite accurately from electron scattering [9], the experimental determinations of r n are typically model dependent [8]. However, the use of parity-violating electron scattering does allow for a nearly model-independent extraction of this quantity [10]. The present value for 208 Pb extracted with this method from the PREX collaboration yields a skin thickness of ∆r np =0.33 +0.16−0.18 fm [11]. Future electron-scattering measurements are expected to reduce the experimental uncertainty.In this work we present an alternative method of determining r n using a dispersive-optical-model (DOM) analysis of bound and scattering data to constrain the nucleon self-energy Σ ℓj . This self-energy is a complex and nonlocal potential that unites the nuclear structure and reaction domains [12,13]. The DOM was originally developed by Mahaux and Sarto...

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“…The density region of the outer core, 0.5ρ0 to 3ρ0, is similar to that found in the nuclear matter environment. Here, we use the Skyrme interactions (blue curves) [27,47,48] [3]. Five interactions, KDE0v1, LNS, NRAPR, SKRA, QMC700, deemed as the best in Ref.…”

Section: Neutron-star Modelmentioning

confidence: 99%

Insights on Skyrme parameters from GW170817

Tsang

Danielewicz

et al. 2019

Physics Letters B

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The binary neutron-star merger event, GW170817, has cast a new light on nuclear physics research. Using a neutron-star model that includes a crust equation of state (EoS), we calculate the properties of a 1.4 solar-mass neutron star. The model incorporates more than 200 Skyrme energy density functionals, which describe nuclear matter properties, in the outer liquid core region of the neutron star. We find a power-law relation between the neutron-star tidal deformability, Λ, and the neutron-star radius, R. Without an explicit crust EoS, the model predicts smaller R and the difference becomes significant for stars with large radii. To connect the neutron star properties with nuclear matter properties, we confront the predicted values for Λ, against the Taylor expansion coefficients of the Skyrme interactions. There is no pronounced correlation between Skyrme parameters in symmetric nuclear matter and neutron star properties.However, we find the strongest correlation between Λ and Ksym, the curvature of the density dependence of the symmetry energy at saturation density. At twice the saturation density, our calculations show a strong correlation between Λ and total pressure providing guidance to laboratory nucleus-nucleus collision experiments.

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Symmetry energy III: Isovector skins

Cited by 70 publications

References 95 publications

Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

Neutron Skin Thickness of Ca48 from a Nonlocal Dispersive Optical-Model Analysis

Insights on Skyrme parameters from GW170817

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