Analysis of p-shell hypernuclei with ΛNN forces and the spin-state dependence of the ΛN effective interaction

From a chi 2 fit to the Lambda binding energy data of p-shell hypernuclei the authors have identified that a zero-range three-body Lambda NN force plays a crucial role in reducing the spin-state dependence of the central charge-independent two-body effective Lambda N potential of Skyrme-type, gaussian, Yukawa and exponential shapes. The exchange contribution of the three-body Lambda NN force to the interaction energy, either ignored altogether or not treated adequately in earlier analyses, has been shown to play an important role. For a Skyrme-type Lambda N potential found from the analysis of p-shell hypernuclei, the authors get a value of 28.52 MeV for Lambda binding to infinite nuclear matter and also Lambda binding in Lambda 5He turns out to be in good agreement with experiment. But the other shapes with reasonable values of the range parameter fail to account for Lambda binding to infinite nuclear matter and BLambda of Lambda 5He even qualitatively. The non-central Lambda N potentials (spin-orbit and tensor force) along with the low spin-state dependence of central two-body charge-independent Lambda N potentials fail to account for the data even qualitatively.