From atoms to nuclei, quarks and bejond...

Latest Results for Few-Body Systems

26 April 2024

• Determination of Nuclear Matter Radii by Means of Microscopic Optical Potentials: The Case of $$^{78}$$ Kr

  Abstract

  In this work we use microscopic Nucleon–Nucleus Optical Potentials (OP) to analyze elastic scattering data for the differential cross section of the \(^{78}\) Kr (p,p) \(^{78}\) Kr reaction, with the goal of extracting the matter radius and estimating the neutron skin, quantities that are both needed to determine the slope parameter L of the nuclear symmetry energy. Our analysis is performed with the factorized version of the microscopic OP obtained in a previous series of papers within the Watson multiple scattering theory at the first order of the spectator expansion, which is based on the underlying nucleon–nucleon dynamics and is free from phenomenological inputs. Differently from our previous applications, the proton and neutron densities are described with a two-parameter Fermi (2pF) distribution, which makes the extraction of the matter radius easier and allows us to make a meaningful comparison with the original analysis, that was performed with the Glauber model. With standard minimization techniques we performed data analysis and extracted the matter radius and the neutron skin. Our analysis produces a matter radius of \(R_m^{\mathrm{(rms)}} = 4.12\)  fm, in good agreement with previous matter radii extracted from \(^{76}\) Kr and \(^{80}\) Kr, and a neutron skin of \(\Delta R_{np} \simeq - 0.1\)  fm, compatible with a previous analysis. Our factorized microscopic OP, supplied with 2pF densities, is a valuable tool to perform the analysis of the experimental differential cross section and extract information such as matter radius and neutron skin. Without any free parameters it provides a reasonably good description of the experimental differential cross section for scattering angles up to \(\approx \) 40 degrees. Compared to the Glauber model our OP can be applied to a wider range of scattering angles and allows one to probe the nuclear systems in a more internal region.

• Positronium Negative Ion Embedded in Non-ideal Classical Plasmas: Doubly Excited Singlet S States

  Abstract

  The effects of the non-ideality (NI) of the classical plasmas on the doubly excited singlet S states in the positronium negative ion (Ps \(^-\) ) are investigated. The organised effect of the plasma is taken care of by means of a pseudopotential which is characterised by the Debye length D and the non-ideality parameter \(\gamma \) . Using an extensive wavefunction within the framework of the stabilization method, it has been possible to identify four doubly excited states (DES) in Ps \(^-\) . The convergence of the energy and the width of those states are corroborated by increasing the number of terms in the wavefunction. Our present calculation for the plasma-free case reproduces the established results. An inclusive study is made to quantify and qualify the changes experienced by the energies and the widths of those states due to the influence of the NI over a wide range. It is observed that the energy of each DES increases and the width of each DES diminishes due to the effect of the increasing NI of the plasma.

• Experiments of Few-Nucleon Scattering to Explore Three-Nucleon Forces

  Abstract

  Few-nucleon scattering offers a good opportunities to study dynamical aspects of three-nucleon forces, that are momentum, spin and isospin dependent. In the paper, the experimental results of deuteron-proton elastic scattering at \(\sim ~\mathrm 100\) MeV/nucleon obtained in the course of the study are presented. The experimental study of few-nucleon scattering has been recently extended to the proton- \(^3 \textrm{He}\) scattering with the aim of approaching the isospin \(T=3/2\) channel in three-nucleon forces. The data are in comparison with the rigorous numerical calculations based on state-of-the-art nuclear potentials with three-nucleon forces.