Orateur
Description
Halo nuclei, where weakly bound nucleons extend far beyond a compact
core, offer a unique window into universal few-body physics near the
limits of nuclear stability. Their properties are controlled by
low-energy parameters, such as separation energies, scattering lengths
and correlations among the valence particles, making them ideal
benchmarks for testing universality in nuclear systems.
We present a four-particle halo model for systems composed of a compact
core and weakly bound particles. The wave function is constructed
from two universal three-body states, each characterized by an
independent binding momentum scale, allowing the effective five-body
system to be built from well-understood few-body building blocks. The
unitary limit serves as the natural reference point, while the formulation
is flexible enough to explore finite-scattering-length effects. This
two-scale structure makes it possible to investigate how three-body
correlations are reorganized within the extended four-particle halo
structure.
The model is first benchmarked against identical bosons, where universal
scaling relations can be tested cleanly. We then apply it to Carbon-22,
treated as a Carbon-18 core plus four valence neutrons organized by two
distinct halo energy scales, with proper antisymmetrization of the halo
neutrons. One-body densities, root-mean-square distances and the matter
radius are computed and expressed in dimensionless form using the relevant
halo momentum scales. The results test the emergence and robustness of
universal scaling behavior across a wide range of scale ratios.