Hyperon-nucleon interaction within chiral effective field theory revisited

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