Investigation of single- and double- Λ hypernuclei using a beyond-mean-field approach

A beyond-mean-field approach consisting of angular momentum projection techniques and generator coordinate method based on Skyrme-Hartree-Fock calculations is employed to investigate single- and double-Λ hypernuclear systems. The density-dependent NΛ interactions derived from the Nijmegen soft-core potentials are used. Rotational energy spectra and electric-quadrupole transition strengths B(E2) of the hypernuclei CΛ13,CΛΛ14,NeΛ21, and NeΛΛ22 are presented and compared with those of the corresponding core nuclei C12 and Ne20. The shrinkage effect of the Λs is demonstrated by the B(E2) values, the charge radii, and the shape deformation β of the nuclear core. It is found that the reduction of the B(E2) values in CΛ13 and CΛΛ14 is mainly caused by the shrinkage of the charge radii of the nuclear cores, while the reduced shape deformations also play important roles; but the contrary is the case in NeΛ21 and NeΛΛ22. Comparison between this and other theoretical models are made, and the differences between them are illuminated.