Abstract
We propose a measurable parameter quantifying the halo nature of one-neutron halo nuclei and investigate the properties of , assuming the core + neutron model for . The parameter is defined by with directly measurable absorption cross sections of , , and scattering at the same incident energy per nucleon. It varies with the one-neutron separation energy in a range of , and the halo structure is most developed when . This situation is realized only for -wave halo nuclei in the limit. We consider and as -wave halo nuclei, and as -wave halo nuclei, and as an example of -wave nonhalo nuclei. For each of halo nuclei, the value of is deduced at a measured from measured total reaction cross sections for , , and scattering at intermediate and high incident energies where projectile breakup effects are negligible. The location of the resulting is plotted in the plane. The empirical values of at the measured are extrapolated to small with model calculations based on the eikonal + adiabatic approximation. In the plane, the model lines are well separated into three groups of -wave halo, -wave halo, and -wave nonhalo particularly in the vicinity of , and the -wave halo lines are always above the other lines, since only the -wave halo lines can reach a point independently of the concrete form of the interaction between and . The relation among the three kinds of lines may be universal for any halo nucleus with small . The point can be regarded as a scale-invariant point in the sense that the -integrated neutron density characterizing halo structure is invariant under the scale transformation there.
2 More- Received 23 February 2016
DOI:https://doi.org/10.1103/PhysRevC.93.064609
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