Imprint of a nuclear bubble in nucleon-nucleus diffraction
V. Choudhary, W. Horiuchi, Masashi Kimura, R. Chatterjee
Abstract
Background: The density of most nuclei is constant in the central region and is smoothly decreasing at the surface. A depletion in the central part of the nuclear density can have nuclear structure effects leading to the formation of ``bubble'' nuclei. However, probing the density profile of the nuclear interior is, in general, very challenging.Purpose: The aim of this paper is to investigate the nuclear bubble structure, with nucleon-nucleus scattering, and quantify the effect that the bubble structure has on the nuclear surface profile.Method: We employed high-energy nucleon-nucleus scattering, using the Glauber model to analyze various reaction observables, which helps in quantifying the nuclear bubble. The effectiveness of this method is tested on $^{28}\mathrm{Si}$ with harmonic-oscillator (HO) densities, before applying it on even-even $N=14$ isotones, in the $22\ensuremath{\le}A\ensuremath{\le}34$ mass range, with realistic densities obtained from antisymmetrized molecular dynamics (AMD).Results: Elastic scattering differential cross sections and reaction probability for the proton-$^{28}\mathrm{Si}$ reaction are calculated using the HO density to design tests for signatures of the nuclear bubble structure. We then quantify the degree of bubble structure for $N=14$ isotones with the AMD densities by analyzing their elastic scattering at 325, 550, and 800 MeV incident energies. The present analyses suggest $^{22}\mathrm{O}$ as the most measurable candidate for a bubble nucleus, among even-even $N=14$ isotones, in the $22\ensuremath{\le}A\ensuremath{\le}34$ mass range.Conclusion: We have shown that the bubble structure information is imprinted on the nucleon-nucleus elastic scattering differential cross section, especially in the first diffraction peak. Bubble nuclei tend to have a sharper nuclear surface and deformation seems to be a hindrance in their emergence.