First observation of $^{13}$Li ground state

TL;DR

This paper reports the first observation of the unbound ground state of neutron-rich $^{13}$Li, reconstructed from decay products, revealing strong dineutron correlations and providing new insights into its decay energy spectrum.

Contribution

The study provides the first experimental observation and detailed analysis of the $^{13}$Li ground state, including its resonance energy and decay correlations, using a novel detection and analysis approach.

Findings

Resonance energy of 120$^{+60}_{-80}$ keV for $^{13}$Li.

Strong dineutron correlations observed in decay.

Decay energy spectrum characterized with an s-wave scattering length > -4 fm.

Abstract

The ground state of neutron-rich unbound $^{13}$Li was observed for the first time in a one-proton removal reaction from $^{14}$Be at a beam energy of 53.6 MeV/u. The $^{13}$Li ground state was reconstructed from $^{11}$Li and two neutrons giving a resonance energy of 120$^{+60}_{-80}$ keV. All events involving single and double neutron interactions in the Modular Neutron Array (MoNA) were analyzed, simulated, and fitted self-consistently. The three-body ($^{11}$Li+$n+n$) correlations within Jacobi coordinates showed strong dineutron characteristics. The decay energy spectrum of the intermediate $^{12}$Li system ($^{11}$Li+$n$) was described with an s-wave scattering length of greater than -4 fm, which is a smaller absolute value than reported in a previous measurement.