Systematic Study Of Elastic Proton-Nucleus Scattering Based On Relativistic Impulse Approximation

Elastic scattering has long been an important experimental technique for studying fundamental nuclear properties,especially bulk properties such as nuclear matter distribution,surface diffuseness,and neutron skin.In recent years,accumulating a large amount of experimental data on elastic scattering,especially on exotic nuclei,has provided an opportunity to test and improve impulse approximation.This paper adopts the relativistic impulse approximation and the PC-PK1 energy density functional calculation as the input for the nuclear density distribution.The proton-nucleus elastic scattering in the incident energy range of 40≤Ep≤200 MeV is systematically studied and compared with the experimental data and the results of the phenomenological optical potential KD03.Based on the machine learning method,the density distribution of 48Ca was reversely derived,and the skin thickness was restricted.The latter is of great value in understanding and constraining nuclear matter’s symmetry energy and density dependence.The specific research content of this paper is summarized as follows:1)Based on the relativistic impulse approximation,elastic proton scattering observables are calculated for Ni and Se isotopes at about 65 MeV using the nuclear density distribution obtained from four sets of widely used energy density functionals.The results show that the overall shape of the densities calculated by the four sets of energy density functionals is similar.However,there are obvious differences in the inner nuclear structure.The corresponding elastic scattering observables are almost identical,indicating that the lowenergy proton-nucleus elastic scattering is less sensitive to the inner nuclear structure.2)We systematically calculate proton-nucleus elastic scattering at 40≤Ep≤200 MeV based on the RIA and a modern density functional PC-PK1.The theoretical results successfully reproduce the experimental data on differential cross sections(dσ/dσRuth.)and analyzing power(Ay)in the mass number range of 12≤A≤232.This confirmed the applicability of the RIA for even-even and nonzero spin nuclei and verified the correlation between the neutron root-mean-square radius and the momentum transfer corresponding to the second minimum of the differential cross section.The density distribution of 48Ca was inversely deduced using a deep neural network method and the RIA.The predicted neutron skin thickness of 48Ca was 0.211±0.007 fm,which overlaps with 48 reasonable energy density functional predictions(0.12-0.26fm)and is larger than the CREX collaboration’s latest experimental value rskin48(CREX)=0.071～0.171 fm.This work provides a reasonable basis for further incorporating ab-initio relativistic chiral force and G-matrix that consider the medium effect into the present RIA framework.Meanwhile,it also explored different approaches for theoretical studies of neutron skin and constraining the nuclear symmetry energy.