Collective excitations of hypernuclei

Hagino, Koichi*; Yao, J. M.*; Minato, Futoshi   ; Li, Z. P.*; Thi Win, M.*

We discuss low-lying collective excitations of hypernuclei using the self-consistent mean-field approaches. We first discuss the deformation properties of hypernuclei in the sd-shell region. Based on the relativistic mean-field approach, we show that the oblate deformation of Si nucleus may disappear when a particle is added to this nucleus. We then discuss the rotational excitations of Mg nucleus using the three-dimensional potential energy surface in the deformation plane obtained with the Skyrme-Hartree-Fock method. The deformation of Mg nucleus is predicted to be slightly reduced due to an addition of particle. We demonstrate that this leads to a reduction of electromagnetic transition probability, , in the ground state rotational band. We also present an application of random phase approximation to hypernuclei, and show that a new dipole mode appears in hypernuclei, which can be interpreted as an oscillation of particle against the core nucleus.