Few-body universality in the deuteron-alpha system

TL;DR

This paper investigates the universal properties of the ${}^6$Li nucleus modeled as a three-body system, revealing a universal correlation between scattering length and binding energy, and proposing ${}^6$Li as a two-nucleon halo nucleus.

Contribution

It demonstrates that ${}^6$Li's properties follow a universal curve in a specific parameter space, supporting its interpretation as a two-nucleon halo nucleus based on few-body universality.

Findings

All calculations lie on a single-parameter curve.

${}^6$Li can be viewed as a two-nucleon halo nucleus.

Universal behavior explains ${}^6$Li's properties.

Abstract

We treat ${}^6$Li as an effective three-body ($n$-$p$-$\alpha$) system and compute the $d$-$\alpha$ $S-$wave scattering length and three-body separation energy of ${}^6$Li for a wide variety of nucleon-nucleon and $\alpha$-nucleon potentials which have the same (or nearly the same) phase shifts. The Coulomb interaction in the $p$-$\alpha$ subsystem is omitted. The results of all calculations lie on a one-parameter curve in the plane defined by the $d$-$\alpha$ $S-$wave scattering length and the amount by which ${}^6$Li is bound with respect to the $n$-$p$-$\alpha$ threshold. We argue that these aspects of the $n$-$p$-$\alpha$ system can be understood using few-body universality and that ${}^6$Li can thus usefully be thought of as a two-nucleon halo nucleus.