Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential

TL;DR

This study compares elastic scattering of $^{120}$Sn with $^6$He and alpha particles, revealing signatures of the $^6$He neutron halo through shifts in reflection coefficients, and proposes a new criterion for identifying halo nuclei.

Contribution

It introduces a method to detect neutron halos in nuclei by analyzing reflection coefficients in elastic scattering data, supported by systematic potential analysis.

Findings

Halo nucleus $^6$He shows distinct reflection coefficient signatures.

The $^6$He optical potential can serve as a basis for a global potential.

Signature of halo is absent in alpha scattering data.

Abstract

Cross sections of $^{120}$Sn($\alpha$,$\alpha$)$^{120}$Sn elastic scattering have been extracted from the $\alpha$ particle beam contamination of a recent $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn experiment. Both reactions are analyzed using systematic double folding potentials in the real part and smoothly varying Woods-Saxon potentials in the imaginary part. The potential extracted from the $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn data may be used as the basis for the construction of a simple global $^6$He optical potential. The comparison of the $^6$He and $\alpha$ data shows that the halo nature of the $^6$He nucleus leads to a clear signature in the reflexion coefficients $\eta_L$: the relevant angular momenta $L$ with $\eta_L \gg 0$ and $\eta_L \ll 1$ are shifted to larger $L$ with a broader distribution. This signature is not present in the $\alpha$ scattering data and can thus be used as a new criterion for the definition of a halo nucleus.