Three-body calculation of the structure of Λ9Be

The hypernucleus Λ9Be is investigated using the α+Λ+α cluster model. The corresponding Faddeev equations are solved for different α-α and Λ-α interactions that describe both 8Be and Λ5He energy spectra. For the ground state Jπ=(1/2)+ and excited states (3/2)+ and (5/2)+ we include the Coulomb repulsion between the α's and calculate, in addition to the energy eigenvalues, the Coulomb energy, the α- and Λ-particle mean radius, the rms charge radius, the electric quadrupole moment (Q), as well as the magnetic dipole (μ) and octopole (μ3) moments. To the best of our knowledge these observables have not yet been measured and, therefore, our calculation constitutes the first prediction. Structural differences between 9Be and Λ9Be lead to values of Q and μ that have opposite sign. Unlike previous theoretical work we find only two degenerate negative parity resonances (1/2)-((3/2)-) but, in addition, we get two degenerate positive parity resonances with Jπ=(7/2)+((9/2)+) at higher energy which, together with the bound states, complete the positive parity rotational band