Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · nucl-th/0209052

Neutron Densities from a Global Analysis of Medium Energy Proton Nucleus Elastic Scattering

B. C. Clark·S. Hama·L. J. Kerr
View original source ↗Read source document ↗Export metadata ↓

Abstract

A new method for extracting neutron densities from intermediate energy elastic proton-nucleus scattering observables uses a global Dirac phenomenological (DP) approach based on the Relativistic Impulse Approximation (RIA). Data sets for Ca40, Ca48 and Pb208 in the energy range from 500 MeV to 1040 MeV are considered. The global fits are successful in reproducing the data and in predicting data sets not included in the analysis. Using this global approach, energy independent neutron densities are obtained. The vector point proton density distribution is determined from the empirical charge density after unfolding the proton form factor. The other densities are parametrized. This work provides energy independent values for the RMS neutron radius, R_n and the neutron skin thickness, S_n, in contrast to the energy dependent values obtained by previous studies. In addition, the results presented in paper show that the expected rms neutron radius and skin thickness for Ca40 is accurately reproduced. The values of R_n and S_n obtained from the global fits that we consider to be the most reliable are given as follows: for Ca40 R_n is 3.314 > R_n > 3.310 fm and S_n is -0.063 > S_n > -0.067 fm; for Ca48 R_n is 3.459 > R_n > 3.413 fm and S_n is 0.102 > S_n > 0.056 fm; and for Pb208 R_n is 5.550 > R_n > 5.522 and S_n is 0.111 > S_n > 0.083 fm. These values are in reasonable agreement with nonrelativistic Skyrme Hartree-Fock models and with relativistic Hartree-Bogoliubov models with density-dependent meson-nucleon couplings. The results from the global fits for Ca48 and Pb208 are generally not in agreement with the usual relativistic mean-field models.

Explore related subjects

nucl-th

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

B. C. Clark, S. Hama, L. J. Kerr. 2003-03-08. Neutron Densities from a Global Analysis of Medium Energy Proton Nucleus Elastic Scattering. https://doi.org/10.1103/physrevc.67.054605

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Fission Modes and Fragment Shell Structures in $^{258}$Md$^*$ from Six-Dimensional Langevin Calculations

The fission of $^{258}$Md$^*$ is calculated in the excitation energy range of $E^*=6$--36 MeV using a six-dimensional Langevin equation. The calculated events are classified into two symmetric and two asymmetric fission modes based on the fragment mass and the quadrupole deformations of the two fragments at scission. The symmetric modes are separated by their total kinetic energies into the short (high TKE) and superlong (low TKE) modes, whereas the asymmetric modes differ in mass asymmetry. With increasing excitation energy, the yield of the short mode decreases, whereas the combined yield of the two asymmetric modes increases, as observed in the in-beam prompt-fission study of $^{258}$Md$^*$. From an analysis of the fragment shapes and associated single-particle levels, the short mode and the dominant asymmetric mode with the smaller mass asymmetry are found to involve a compact fragment characterized by deformed shell gaps at $Z=52$ and $N=84$, while the complementary fragments have different quadrupole deformations in the two modes.

nucl-th↗
arXiv2026

Classification of fission modes in $^{236}$U using a six-dimensional Langevin approach

Thermal neutron-induced fission of $^{235}$U is studied using a six-dimensional Langevin approach based on the Cassini shape parametrization. Scission events are classified into Asymmetric 1 (AS1), Asymmetric 2 (AS2), and Superlong (SL) fission modes by applying the $k$-means algorithm to the fragment mass and the quadrupole deformations of both fragments. For each mode, proton and neutron single-particle levels are calculated for representative fragments to examine their shell structures. The AS1 heavy fragment exhibits proton gaps at $Z=50$ and 52 and neutron gaps at $N=82$ and 84, whereas well-developed gaps appear at $Z=56$ and $N=88$ in the AS2 heavy fragment. The mass splits of AS1 and AS2 are close to those of the conventional Standard I and Standard II modes, respectively. However, the average total kinetic energy is lower for AS1 than for AS2, opposite to the conventional ordering of Standard I and Standard II. This reversal reflects the more elongated shape of the AS1 light fragment. The SL mode is conventionally interpreted in terms of macroscopic liquid-drop effects, whereas the pronounced proton shell gap at $Z=46$ suggests that proton shell effects also contribute to the elongated symmetric configuration. The classification based on fragment mass and the quadrupole deformations of both fragments provides a basis for distinguishing fission modes and examining the corresponding fragment shell structures at scission.

nucl-th↗
arXiv2026

Gogny interaction from beginnings to current challenges

The main goal of the present review article is to gather for the first time various facets of the phenomenological effective Gogny interaction which was originally proposed in the 70's. This involves both nuclear phenomena of interest that led to its creation and evolution as well as highly technical aspects that led the objectives to be achieved. With this in mind, we propose a discussion structured around four points. After a general introduction, the history and philosophy of the Gogny interaction is exposed. In particular, one highlights an intuitive way of guiding the determination of the parameters of the phenomenological interaction with the results obtained from a realistic interaction using Hartree-Fock calculations and second order corrections and a G-matrix. One also shows that physical phenomena such as pairing or fission were essential to improve the parameterization. The evolution of the original analytical form over the years is also discussed. The second point concern the emulator that was used for the generation of parameterizations. Its modifications, consistent with the evolution of the analytical form, are given. Other fitting procedures, more recent, are also evoked. The third key point is dedicated to the role of the nuclear matter in the fitting process and the acceptance of a parameterization. The objective of the last key point is to highlight some results obtained with the Gogny interaction in nuclear structure, fission and reactions that have allowed to interpret experimental data.

nucl-th↗