Long-range chiral dynamics of $Λ$-hyperon in nuclear media

Abstract

We extend a chiral effective field theory approach to the $Λ$-nuclei interaction with the inclusion of the decuplet baryons. More precisely, we study the contributions due to the long-range two-pion exchange, with $Σ$ and $Σ^*$ baryons in the internal baryonic lines considering Nh and $Δ$h excitations. In particular, central and spin-orbit potentials are studied. For the former, regularization is needed and physical values of the cut-off give a large attraction, becoming necessary to include the repulsion of other terms not considered here. For the latter, in a model-independent framework, the inclusion of the decuplet supports the natural explanation of the smallness of the $Λ$-nuclear spin-orbit term and shows the importance of the $Σ^*$ and $Δ$ degrees of freedom for the hyperon-nucleus interactions.