Comment le noyau de magnésium se fait un manteau de neutrons express

Résumé original

tel que rédigé par les auteurs, en anglais arXiv:2608.09429v2

Involving the charge radii of \rm Mg isotopes, as calculated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), we have extracted the neutron radii of $$^{24-38}$$\rm Mg isotopes by studying their reaction cross sections ($$\sigma_{R}$$) from $$^{12}$$\rm C at 240 MeV/nucleon within the framework of Glauber model. The calculations use (i) descriptions of nuclei in terms of the Slater determinant involving harmonic oscillator single-particle wave functions (SDHO), and (ii) two-parameter Fermi (2pF) shape of density distribution, with the aim to assess the density dependence of neutron skin in $$^{24-38}$$\rm Mg isotopes. To understand the asymptotic behavior (spread) of neutron distribution, we propose to introduce the use of core+n ($$S_{n}S_{2n}$$) description for stable as well as unstable isotopes; $$S_{n}$$ ($$S_{2n}$$) is the one-neutron (two-neutron) separation energy of the considered isotope. The core+n (core+2n) is treated semi-phenomenologically. In this work, the core+n is employed for $$^{25-38}$$\rm Mg isotopes, and is subjected to reproduce the same neutron radius of the given isotope, as we obtained from $$\sigma_{R}$$ calculations. To validate the core+n description, we have revisited the reaction cross sections of $$^{25-38}$$\rm Mg isotopes. The results are found to agree well with the experimental values. Moreover, the core+n neutron distributions clearly demonstrate the one-neutron halo structure of $$^{37}$$\rm Mg. These findings motivated us to use the core+2n description for the neutron distribution of $$^{40}$$\rm Mg in predicting its neutron radius, and $$\sigma_{R}$$ from $$^{12}$$\rm C at 240 and 1000 MeV/nucleon. The trend of the neutron radius and $$\sigma_{R}$$ suggests that $$^{40}$$\rm Mg exhibits two-neutron halo like structure.