Excited states of Λ9Be and ΛΛ10Be in an α cluster model

The energies of the degenerate spin-flip doublet (3+/2,5+/2) of Λ9Be and of the 2+ state of ΛΛ10Be are analyzed in the α cluster model using a phenomenological dispersive three-body Λαα force that reproduces the ground state energy of Λ9Be. Two types of phenomenological Λα and αα potentials and a few s-state ΛΛ potentials are taken as input. The energies of the excited states of the hypernuclei, treated as three- and four-body systems, calculated using the Variational Monte Carlo method, are in good agreement with the experimental values. Our results demonstrate that the existing data are insensitive to whether one employs a dispersive Λαα force along with potentials in the relative angular momentum state l=0 and 2 as in the present work or whether one uses nonlocal Λα potential as in earlier analyses