Constraints on the symmetry energy and neutron skins from pygmy resonances in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Ni</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>68</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Sn</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>132</mml:mn></

Carbone, Andrea; Colò, G.; Bracco, A.; Cao, Lei; Bortignon, P. F.; Camera, F.; Wieland, O.

doi:10.1103/physrevc.81.041301

Cited by 336 publications

(353 citation statements)

References 38 publications

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“…In addition to the identification of the prominent Giant Dipole Resonance (GDR), the electric dipole response of neutron-rich nuclei displays a smaller concentration of strength at lower energies, that is commonly referred to as the Pygmy Dipole Strength (PDS) [5]. Data on the PDS have been used in the past to constrain the symmetry energy and to obtain * xavier.roca.maza@mi.infn.it information on the neutron skin thickness of neutronrich nuclei [6][7][8][9][10][11]. In one of the earliest applications of uncertainty quantification to the domain of energy density functionals (EDFs), Reinhard and Nazarewicz carried out a covariance analysis to correlate the neutron skin thickness of 208 Pb to the properties of both finite nuclei and infinite nuclear matter [1].…”

Section: Introductionmentioning

confidence: 99%

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
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The information on the symmetry energy and its density dependence is deduced by comparing the available data on the electric dipole polarizability αD of 68 Ni, 120 Sn, and 208 Pb with the predictions of Random Phase Approximation, using a representative set of nuclear energy density functionals.The calculated values of αD are used to validate different correlations involving αD, the symmetry energy at the saturation density J, corresponding slope parameter L and the neutron skin thickness ∆rnp, as suggested by the Droplet Model. A subset of models that reproduce simultaneously the measured polarizabilities in 68 Ni, 120 Sn, and 208 Pb are employed to predict the values of symmetry energy parameters at saturation density and ∆rnp. The resulting intervals are: J = 30-35 MeV, L = 20-66 MeV; and the values for ∆rnp in 68 Ni, 120 Sn, and 208 Pb are in the ranges: 0.15-0.19 fm, 0.12-0.16 fm, and 0.13-0.19 fm, respectively. The strong correlation between the electric dipole polarizabilities of two nuclei is instrumental to predict the values of electric dipole polarizabilities in other nuclei.

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Section: Introductionmentioning

confidence: 99%

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
View full text Add to dashboard Cite

show abstract

“…Isospin diffusion predicts L = 88± 25 MeV [8,9], nucleon emission ratios [10] favor a value closer to L ∼ 55 MeV, isoscaling gives L ∼ 65 MeV [11]. Analysis of giant dipole resonance (GDR) of 208 Pb [12] is suggestive of L ∼ 45-59 MeV, whereas pygmy dipole resonance [13] in 68 Ni and 132 Sn would yield an weighted average in the range L= 64.8± 15.7 MeV. Of late, from a sensitive fit of the experimental nuclear masses to those obtained in the finite-range droplet model [1], the value of L could be fixed in the bound L = 70 ±15 MeV.…”

mentioning

confidence: 99%

Determining the Density Content of Symmetry Energy and Neutron Skin: An Empirical Approach

Agrawal

Samaddar

2012

Phys. Rev. Lett.

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The density dependence of nuclear symmetry energy remains poorly constrained. Starting from precise empirical values of the nuclear volume and surface symmetry energy coefficients and the nuclear saturation density, we show how in the ambit of microscopic calculations with different energy density functionals, the value of the symmetry energy slope parameter L alongwith that for neutron skin can be put in tighter bounds. The value of L is found to be L= 64±5 MeV. For 208 Pb, the neutron skin thickness comes out to be 0.188 ±0.014 fm. Knowing L, the method can be applied to predict neutron skins of other nuclei. In recent times, there is a cultivated focus on a better understanding of the density properties of the symmetry energy of nuclear matter. Particular attention is given to constrain in a narrow window the value of the symmetry energy slope parameter L at the nuclear matter saturation density ρ 0 . In terrestrial context, this parameter affects the nuclear binding energies [1] and the nuclear drip lines and has a crucial role in determining the neutron density distribution in neutron-rich nuclei. In astrophysical context, it is also of seminal importance. The pressure P n (=3ρ 0 L) of neutron matter at ρ 0 influences the radii of cold neutron stars. The cooling of proto-neutron stars through neutrino convection [2], the dynamical evolution of the core-collapse of a massive star and the associated explosive nucleosynthesis depend sensitively on the symmetry energy slope parameter [3,4]. In the droplet model [5,6] of the nucleus, the neutron skin is proportional to L, a linear correlation between the neutron-skin thickness of the nucleus and neutron-star radius [7] could thus be envisaged.The symmetry energy slope parameter is defined aswhere Correlation systematics of nuclear isospin with the neutron skin thickness [15,16] for a series of nuclei in the framework of the nuclear droplet model has been undertaken by the Barcelona Group. This has yielded a value of L =75 ±25 MeV. The neutron skins were measured from antiprotonic atom experiments [17,18], systematic uncertainties involving model assumptions to deal with strong interaction is therefore unavoidable. The novel Pb-radius experiment (PREX) at the Jefferson Laboratory has now been attempted through parity-violation in electron scattering as a model-independent probe of the neutron density in 208 Pb [19]. The neutron skin R skin = R n − R p was found to be 0.33 +0.16 −0.18 fm, where R n and R p are the point neutron and proton root-mean squared (rms) radii. A reanalysis yielded the value to be 0.302 ±0.175 fm [20]. The droplet model as well as calculations with class of different interactions, Skyrme or relativistic mean-field (RMF), have now clearly established that the neutron skin thickness of 208 Pb is strongly correlated with the density dependence of symmetry energy around saturation [21][22][23][24]. In the backdrop of this information, the large uncertainty in the experimental neutron radius of 208 Pb seems to be of not much help in putting L i...

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“…Analyses of isospin diffusion in heavy-ion collisions give 0.22±0.04 fm [38]. A recent prediction based on measurements of the pygmy dipole resonance in lighter nuclei gives 0.194±0.024 fm in 208 Pb [39][40][41]. However the interpretation of this resonance and the model dependence of the result is still a matter of discussion [42].…”

Section: Coherent S S 0 Production Experimentsmentioning

confidence: 98%

Research with real photons at the MAMI 1.6 GeV electron accelerator

MacGregor

2014

EPJ Web of Conferences

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Abstract. The A2-CB Collaboration at Mainz is studying the structure of hadrons by meson photoproduction using unpolarised, linearly polarised and circularly polarised photons with energies up to 1.6 GeV. Photons are energy-tagged using the Glasgow-Mainz tagged photon spectrometer and a new high-energy end-point tagger which allows K' reactions to be studied. Reaction products are detected in a ~4S detector consisting of the Crystal Ball detector and TAPS forward wall. Transverse or longitudinally polarised proton targets are available and new techniques have been developed to measure the polarisation of recoiling protons. These facilities have allowed an extensive programme of double-polarisation meson-photoproduction experiments to be carried out to search for so-called "missing baryon resonances" on proton and deuteron targets. Searches have also been carried out to investigate narrow resonances in the K-photoproduction channel at invariant masses around 1680 MeV. Coherent S 0 production measurements have been used to estimate the neutron skin thickness in 208 Pb. This paper presents selected highlights from the A2-CB collaboration research programme at MAMI.

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Constraints on the symmetry energy and neutron skins from pygmy resonances inNi68andSn132

Cited by 336 publications

References 38 publications

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
View full text Add to dashboard Cite

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
View full text Add to dashboard Cite

Determining the Density Content of Symmetry Energy and Neutron Skin: An Empirical Approach

Research with real photons at the MAMI 1.6 GeV electron accelerator

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Constraints on the symmetry energy and neutron skins from pygmy resonances inNi68andSn132

Cited by 336 publications

References 38 publications

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, andRoca-Maza1, Viñas2, Centelles3 et al. 2015Phys. Rev. C238322563View full textAdd to dashboardCite

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, andRoca-Maza1, Viñas2, Centelles3 et al. 2015Phys. Rev. C238322563View full textAdd to dashboardCite

Determining the Density Content of Symmetry Energy and Neutron Skin: An Empirical Approach

Research with real photons at the MAMI 1.6 GeV electron accelerator

Contact Info

Product

Resources

About

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
View full text Add to dashboard Cite

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, and
Roca-Maza
¹
,
Viñas
²
,
Centelles
³

et al. 2015
Phys. Rev. C
238
32
256
3
View full text Add to dashboard Cite