This paper presents a detailed assessment of the ability of the 240 Skyrme interaction parameter sets in the literature to satisfy a series of criteria derived from macroscopic properties of nuclear matter in the vicinity of nuclear saturation density at zero temperature and their density dependence, derived by the liquid-drop model, in experiments with giant resonances and heavy-ion collisions. The objective is to identify those parametrizations which best satisfy the current understanding of the physics of nuclear matter over a wide range of applications. Out of the 240 models, only 16 are shown to satisfy all these constraints. Additional, more microscopic, constraints on the density dependence of the neutron and proton effective mass β-equilibrium matter, Landau parameters of symmetric and pure neutron nuclear matter, and observational data on high- and low-mass cold neutron stars further reduce this number to 5, a very small group of recommended Skyrme parametrizations to be used in future applications of the Skyrme interaction of nuclear-matter-related observables. Full information on partial fulfillment of individual constraints by all Skyrme models considered is given. The results are discussed in terms of the physical interpretation of the Skyrme interaction and the validity of its use in mean-field models. Future work on application of the Skyrme forces, selected on the basis of variables of nuclear matter, in the Hartree-Fock calculation of properties of finite nuclei, is outlined.

Skyrme interaction and nuclear matter constraints

Experimental studies of the Pygmy Dipole Resonance

In this review, we discuss the present status of three indirect techniques that are used to determine reaction rates for stellar burning processes, asymptotic normalization coefficients, the Trojan Horse method and Coulomb dissociation. A comprehensive review of the theory behind each of these techniques is presented. This is followed by an overview of the experiments that have been carried out using these indirect approaches.

https://iopscience.iop.org/article/10.1088/0034-4885/77/10/106901/pdf

Indirect techniques in nuclear astrophysics: a review

Nuclear equation of state from ground and collective excited state properties of nuclei

The properties of large volume cylindrical 3.5″×8″ (89 mm×203 mm) LaBr 3 :Ce scintillation detectors coupled to the Hamamatsu R10233-100SEL photo-multiplier tube were investigated. These crystals are among the largest ones ever produced and still need to be fully characterized to determine how these detectors can be utilized and in which applications. We tested the detectors using monochromatic γ–ray sources and in-beam reactions producing γ rays up to 22.6 MeV; we acquired PMT signal pulses and calculated detector energy resolution and response linearity as a function of γ-ray energy. Two different voltage dividers were coupled to the Hamamatsu R10233-100SEL PMT: the Hamamatsu E1198-26, based on straightforward resistive network design, and the “LABRVD”, specifically designed for our large volume LaBr 3 :Ce scintillation detectors, which also includes active semiconductor devices. Because of the extremely high light yield of LaBr 3 :Ce crystals we observed that, depending on the choice of PMT, voltage divider and applied voltage, some significant deviation from the ideally proportional response of the detector and some pulse shape deformation appear. In addition, crystal non-homogeneities and PMT gain drifts affect the (measured) energy resolution especially in case of high-energy γ rays. We also measured the time resolution of detectors with different sizes (from 1″×1″ up to 3.5″×8″), correlating the results with both the intrinsic properties of PMTs and GEANT simulations of the scintillation light collection process. The detector absolute full energy efficiency was measured and simulated up to γ-rays of 30 MeV

Characterization of large volume 3.5″×8″ LaBr3:Ce detectors

The $\ensuremath{\gamma}$ decay from Coulomb excitation of $^{68}\mathrm{Ni}$ at $600\text{ }\text{ }\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a Au target was measured using the RISING setup at the fragment separator of GSI. The $^{68}\mathrm{Ni}$ beam was produced by a fragmentation reaction of $^{86}\mathrm{Kr}$ at $900\text{ }\text{ }\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a $^{9}\mathrm{Be}$ target and selected by the fragment separator. The $\ensuremath{\gamma}$ rays produced at the Au target were measured with HPGe detectors at forward angles and with ${\mathrm{BaF}}_{2}$ scintillators at backward angles. The measured spectra show a peak centered at approximately 11 MeV, whose intensity can be explained in terms of an enhanced strength of the dipole response function (pygmy resonance). Such pygmy structure has been predicted in this unstable neutron-rich nucleus by theory.

H. Emling

Papers

Search for the pygmy dipole resonance in 68Ni at 600 MeV/nucleon.