Ab initio description of hypernuclei

TL;DR

This paper reviews recent ab initio methods for describing hypernuclei, highlighting the role of chiral effective field theory and the importance of three-body forces in accurately predicting hypernuclear properties.

Contribution

It provides an overview of ab initio approaches using chiral EFT for hypernuclei, including explicit results and insights into the importance of three-body forces.

Findings

Agreement with experimental binding energies improves with three-body forces.

Calculations up to A=7 with NCSM and up to A=16 with NLEFT are feasible.

Possible bound states include $^{ ext{5}}_{ ext{ΛΛ}}$He and $^4_ ext{Ξ}$H.

Abstract

Hypernuclei are bound states of neutrons, protons and one or two hyperons, thus extending the nuclear landscape to a third dimension. They also encode information about the baryon-baryon and three-baryon interactions. Here, we review recent work on chiral effective field theory for two- and three-baryon interactions and their application in nuclei based on ab initio methods. These include the Faddeev-Yakubovsky equations, the no-core-shell-model (NCSM) and nuclear lattice effective field theory (NLEFT). Besides of providing an overview of the formalisms explicit results for the separation energies of light $\Lambda$ hypernuclei are provided. Two-body and three-body forces are included consistently, in line with the underlying power counting. Calculations of $\Lambda$ hypernuclei within the NCSM, performed up to A=7 so far, suggest that agreement with the experimental binding energies can be achieved once appropriate three-body forces are taken into account. Similar conclusions are drawn from the study based on NLEFT, where even hypernuclei up to A=16 can be computed. Additionally, applications of ab initio approaches in calculations of $\Lambda \Lambda$ and $\Xi$ hypernuclei are discussed and possible candidates for the lightest systems that could be bound are identified, namely $^{\ \ 5}_{\Lambda \Lambda}{\rm He}$ and $^4_\Xi{\rm H}$.