Hyperon–nucleon interaction within chiral effective field theory revisited

The $$\varLambda N$$ and $$\varSigma N$$ 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 $$\varLambda N$$ and $$\varSigma N$$ scattering observables but differ in the strength of the $$\varLambda N \rightarrow \varSigma N$$ transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the $$\varLambda $$ and $$\varSigma $$ hyperons in nuclear matter is investigated and discussed. The effect of the variation in the potential strength of the $$\varLambda N$$-$$\varSigma N$$ coupling (also called $$\varLambda -\varSigma $$ conversion) is found to be moderate for the considered $$^3_\varLambda {{\mathrm{H}}}$$ and $$^4_\varLambda \mathrm{He}$$ 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.