In this talk I review recent experimental evidence presented by the FINUDA Collaboration in the e+e --> Phi --> K+K- DAFNE machine at Frascati, Italy, for a particle stable Lambda-6H, with one proton and four neutrons stabilized by a Lambda hyperon [1]. Ongoing few-body calculations of Lambda-6H as well as shell-model estimates for its stability will also be briefly reviewed. The Lambda-6H hypernucleus was highlighted by Akaishi [2] as a test ground for the significance of Lambda N Sigma N coupling in Lambda hypernuclei, spurred by the role it plays in s-shell hypernuclei and by the far-reaching consequences it might have for dense neutron-star matter with strangeness. The discovery of Lambda-6H has stirred renewed interest in charting domains of particle-stable neutron-rich Lambda hypernuclei, particularly for unbound nuclear cores.
Millener and I have studied within a shell-model approach several neutron rich Lambda hypernuclei in the nuclear p shell that could be formed in (pi-,K+) (ongoing experiment E10 at J-PARC, Japan) or in (K-,pi+) reactions on stable nuclear targets. The hypernuclear shell-model input was taken from a theoretically inspired successful fit of gamma-ray transitions in p-shell Lambda hypernuclei. Predictions for binding energies of Lambda-9He, Lambda-10Li, Lambda-12Be and Lambda-14B will be reviewed, concluding that none of the large effects conjectured by Akaishi to arise from Lambda N Sigma N coupling is borne out by our realistic shell-model calculations.
