Three-body calculation of the structure of Λ9Be -: art. no. 014001

The hypernucleus Be-9(Lambda) is investigated using the alpha+Lambda+alpha cluster model. The corresponding Faddeev equations are solved for different alpha-alpha and Lambda-alpha interactions that describe both Be-8 and He-5(Lambda) energy spectra. For the ground state J(pi)=1/2(+) and excited states 3/2(+) and 5/2(+) we include the Coulomb repulsion between the alpha's and calculate, in addition to the energy eigenvalues, the Coulomb energy, the alpha- and Lambda-particle mean radius, the rms charge radius, the electric quadrupole moment (Q), as well as the magnetic dipole (mu) and octopole (mu(3)) 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 Be-9 and Be-9(Lambda) lead to values of Q and mu 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 J(pi)=7/2(+)(9/2(+)) at higher energy which, together with the bound states, complete the positive parity rotational band.