Simple model for a study of Λ hypernuclei in medium and heavy mass regions

Abstract

We propose a simple and versatile model of Λ hypernuclei in the medium and heavy mass regions to obtain their low-lying energy levels and electromagnetic transitions. In this model we treat the inert core nucleus as a simple indivisible union of nucleons and its properties are taken from the experimental data. The interaction of the core nucleus and the Λ particle is assumed to be weak and treated perturbatively. We study medium and heavy Λ hypernuclei, 51ΛV, 52ΛV, 89ΛY, 139ΛLa, and 208ΛPb. To check its applicability for a lighter hypernucleus, we apply the model to 19ΛF, where γ-ray transitions are experimentally observed. The present study demonstrates that the low-lying excited states of the core nucleus below 2 MeV in addition to the ground state of the core nucleus should be included in the calculations for the spectra and electromagnetic transitions in the low-lying states of the Λ hypernuclei. This model helps us to theoretically study those medium and heavy hypernuclei where large-scale shell-model studies are intractable to carry out.