Two neutron decay of 16Be

TL;DR

This paper models the two-neutron decay of the unbound nucleus $^{16}$Be using three-body methods, revealing the importance of three-body forces and providing detailed decay characteristics.

Contribution

It introduces a realistic three-body model of $^{16}$Be using hyperspherical harmonics and R-matrix methods, highlighting the role of three-body forces in decay.

Findings

$^{16}$Be$'$s ground state is over-bound by ~1 MeV.

Decay width of approximately 0.23 MeV.

Three-body force likely needs to be repulsive.

Abstract

Recently, the first example of two-neutron decay from the ground state of an unbound nucleus, $^{16}$Be, was seen. Three-body methods are ideal for exactly treating the degrees of freedom important for these decays. Using a basis expansion over hyperspherical harmonics and the hyperspherical R-matrix method, we construct a realistic model of $^{16}$Be in order to investigate its decay mode and the role of the two-neutron interaction. The neutron-$^{14}$Be interaction is constrained using shell model predictions. We obtain a ground state for $^{16}$Be that is over-bound by approximately 1 MeV with a width of approximately 0.23 MeV. This suggests, that for such systems, the three-body force needs to be repulsive.