Few-Body Systems最新文献

Several astrophysical processes are governed by the occurrence of nuclear reactions involving light nuclei at energies below the Coulomb barrier. Among other effects, their understanding is challenged by the appearance of clustered structures in the ground-state configuration of some of these nuclei, which may have a significant impact on the reaction cross section. In this contribution, we focus on the (^6{textrm{Li}})(({textrm{p}}), (^3{textrm{He}}))(^4{textrm{He}}) reaction, to probe the role of clustered configurations of (^6{textrm{Li}}). In particular, we consider a three-body ab-initio calculation, based on the hyperspherical harmonics (HH) method, of the (^6{textrm{Li}}) wave function (WF), together with a more phenomenological three-body model. We observe that the HH WF entails a degree of clustering much larger than obtained from the phenomenological WFs. However, the corresponding reaction cross section, evaluated as a direct two-nucleon transfer in distorted-wave Born approximation, still follows the scaling with the clustering strength already pointed out in a previous work (Perrotta et al. in Phys Rev C 108(4), 044614, 2023, https://doi.org/10.1103/PhysRevC.108.044614) and exhibits an energy trend very similar to that obtained with realistic phenomenological WFs. This opens up interesting perspectives towards constraining the extent of clustering effects in ground state configurations from the comparison to cross-section experimental data.

Geometrical structures of low-energy states in the ({}^{12})C nucleus are investigated using density distributions obtained from three (alpha )-particle wave functions calculated for a set of phenomenological (2alpha )- and (3alpha ) potentials by Faddeev technique. Calculated shapes of triangles that three (alpha )-particles form are classified to either an equilateral triangle, an isosceles triangle, or a mixture of these with various sizes, which may characterize the excitation mechanism of the states

We present a coupled-cluster calculation for the electron-(^4)He scattering in the region of the quasi-elastic peak. We show the longitudinal and transverse responses separately, and discuss results within two distinct theoretical methods: the Lorentz integral transform and spectral functions. The comparison between them allows to investigate the role of final state interactions, two-body currents and relativistic effects.

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.

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.

The spin correlation coefficients in the neutron-deuteron elastic scattering process at incoming neutron laboratory energies (hbox {E}=10), 135, 190, and 250 MeV are determined by solving the momentum space three-nucleon (3N) Faddeev equations. The chiral two-nucleon (2N) interaction with momentum-space semi-local (SMS) regularization up to the fifth order of chiral expansion ((hbox {N}^4hbox {LO})), supplemented by the F-waves terms from the sixth order ((hbox {N}^5hbox {LO})), is used. Additionally, the consistent 3N force (3NF) at the third order of chiral expansion, supplemented by the short-range contributions from (hbox {N}^4hbox {LO}) is applied. As a results, we give predictions for the complete set of spin correlation coefficients (C_{alpha ,beta }). We find that the effect of the investigated three-nucleon (hbox {N}^4hbox {LO}) components amounts up to several dozen percent, depending on reaction energy, scattering angle and type of spin correlation coefficient itself. Our results can serve as a guide for future measurements of the spin correlation coefficients.

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.

A new quantization is proposed for an energy-dependent particle exchange potential. The quantum number corresponds not only to the branch point of the potential cut, but also to the index of a long-range hadron potential. By using the long-range potential, an ultra-low energy nuclear (ULEN) reaction is investigated. It was found that a three-body Cs + H + H plasma in a Pd(_{12}) cage could be excited to (1.36times 10^{-4}) eV (sim 300) eV by an electric current where the long-range potential gives one or two order larger reaction probability than the others. A ULEN reaction was compared with the thermo-nuclear fusion by using well-known critical fusion constant defined by (C_{high/low}) = (a duration time) (times ) (a plasma density) (times ) (a temperature). We found that (C_{low}) is almost the same as (C_{high}) or more. We concluded that the ULEN synthesis could occur with a high-pressure hydrogen circumstance and a high-density CsH(_2)Pd(_{12}) cluster.