Separation energies of lighthypernuclei and their theoretical uncertainties

Separation energies of light Lambda hypernuclei (A <= 5) and their theoretical uncertainties are investigated. Few-body calculations are performed within the Faddeev-Yakubovsky scheme and the no-core shell model. Thereby, modern and up-to-date NN and YN potentials derived within chiral effective field theory are employed. % It is found that the numerical uncertainties of the few-body methods are well under control and an accuracy of around 1 keV for the hypertriton and of less than 20 keV for the separation energies of the 4 Lambda He and 5 Lambda He hypernuclei can be achieved. Variations caused by differences in the NN interaction are in the order of 10 keV for 3 Lambda H and no more than 110 keV for A=4,5 Lambda hypernuclei, when recent high-precision potentials up to fifth order in the chiral expansion are employed. The variations are smaller than expected contributions from chiral YNN three-body forces (3BFs) which arise at the chiral order of state-of-the-art YN potentials. Estimates for those 3BFs are deduced from a study of the truncation uncertainties in the chiral expansion.