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Hyperon-nucleon interaction within chiral effective field theory revisited

The $ΛN$ and $ΣN$ interactions are considered at next-to-leading order in SU(3) chiral effective field theory. Different options for the low-energy constants that determine the strength of the contact interactions are explored. Two variants are analysed in detail which yield equivalent results for $ΛN$ and $ΣN$ scattering observables but differ in the strength of the $ΛN \to ΣN$ transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the $Λ$ and $Σ$ hyperons in nuclear matter is investigated and discussed. The effect of the variation in the potential strength of the $ΛN$-$ΣN$ coupling (also called $Λ-Σ$ conversion) is found to be moderate for the considered $^3_Λ\rm H$ and $^4_Λ\rm He$ hypernuclei but sizable in case of the matter properties. Further, the size of three-body forces and their relation to different approaches to hypernuclear interactions is discussed.