Density Functional approach for multi-strange hypernuclei: competition between $Λ$ and $Ξ^{0,-}$ hyperons

Abstract

The question of the competition between $Λ$ and $Ξ^{0,-}$ in the ground-state of multi-strange hypernuclei is addressed within a non-relativistic density functional approach, partially constrained by ab-initio calculations and experimental data. The exploration of the nuclear chart for $10<Z<120$ as a function of the strangeness number is performed by adding hyperons to a nuclear core imposing either conserved total charge $Q$ or conserved proton number $Z$. We find that almost all $Λ$ hypernuclei present an instability with respect to the strong interaction decay of $Λ$ towards $Ξ^{0,-}$ and that most of the instabilities generates $Ξ^-$ (resp. $Ξ^0$) in the case of conserved total charge $Q$ (resp. proton number $Z$). The strangeness number at which the first $Ξ^{0,-}$ appear is generally lower for configurations explored in the case of conserved $Q$ compared to the case of conserved $Z$, and corresponds to the crossing between the $Λ$ and the neutron or proton chemical potentials. About two to three hundred thousands pure $Λ$ hypernuclei may exist before the onset of $Ξ^{0,-}$. The largest uncertainty comes from the unknown $ΛΞ$ interaction, since the $NΛ$ and the $NΞ$ ones can be constrained by a few experimental data. The uncertainty on the $ΛΞ$ interaction can still modify the previous estimation by 30-40\%, while the impact of the unknown $ΞΞ$ interaction is very weak.