Neutron-rich hypernuclei: Lambda-6H and beyond

TL;DR

This paper investigates neutron-rich Lambda hypernuclei using a shell-model approach, providing predictions for their stability and binding energies, and challenging previous claims about the effects of Lambda-Sigma coupling.

Contribution

It offers a detailed shell-model analysis of neutron-rich Lambda hypernuclei, including predictions for their stability and binding energies, with a focus on the role of Lambda-Sigma coupling.

Findings

Lambda-6H is particle-stable according to recent evidence.

Predicted binding energies for Lambda-9He, Lambda-10Li, Lambda-12Be, Lambda-14B.

Lambda-Sigma coupling effects are not as significant as previously conjectured.

Abstract

Recent experimental evidence presented by the FINUDA Collaboration for a particle-stable Lambda-6H has stirred renewed interest in charting domains of particle-stable neutron-rich Lambda hypernuclei, particularly for unbound nuclear cores. We have studied within a shell-model approach several neutron-rich Lambda hypernuclei in the nuclear p shell that could be formed in (pi-,K+) or in (K-,pi+) reactions on stable nuclear targets. Hypernuclear shell-model input is taken from a theoretically inspired successful fit of gamma-ray transitions in p-shell Lambda hypernuclei which includes also Lambda-N <-> Sigma-N coupling (Lambda<->Sigma coupling). The particle stability of Lambda-6H is discussed and predictions are made for binding energies of Lambda-9He, Lambda-10Li, Lambda-12Be, Lambda-14B. None of the large effects conjectured by some authors to arise from Lambda<->Sigma coupling is borne out, neither by these realistic p-shell calculations, nor by quantitative estimates outlined for heavier hypernuclei with substantial neutron excess.