Correlated two-neutron emission in the decay of unbound nucleus 26O

TL;DR

This paper investigates the decay of the unbound nucleus 26O, revealing strong neutron-neutron correlations and dineutron emission patterns through a three-body decay model, emphasizing the role of neutron interactions.

Contribution

It introduces a three-body decay model for 26O that highlights the significance of neutron-neutron interactions and dineutron correlations in its decay process.

Findings

Neutron-neutron final state interaction significantly affects the decay spectrum.

Evidence of strong neutron-neutron correlation in the decay.

Enhanced back-to-back two-neutron emission indicating dineutron formation.

Abstract

The particle unbound $^{26}$O nucleus is located outside the neutron drip line, and spontaneously decays by emitting two neutrons with a relatively long life time due to the centrifugal barrier. We study the decay of this nucleus with a three-body model assuming an inert $^{24}$O core and two valence neutrons. We first point out the importance of the neutron-neutron final state interaction in the observed decay energy spectrum. We also show that the energy and and angular distributions for the two emitted neutrons manifest a clear evidence for the strong neutron-neutron correlation in the three-body resonance state. In particular, we find an enhancement of two-neutron emission in back-to-back directions. This is interpreted as a consequence of {\it dineutron correlation}, with which the two neutrons are spatially localized before the emission.