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-Lambda hypernuclear systems. The density-dependent N Lambda interactions derived from the Nijmegen soft-core potentials are used. Rotational energy spectra and electric-quadrupole transition strengths B(E2) of the hypernuclei C-13(Lambda), C-14(Lambda Lambda), Ne-21(Lambda), and Ne-22(Lambda Lambda) are presented and compared with those of the corresponding core nuclei 12C and 20Ne. The shrinkage effect of the Lambda s is demonstrated by the B(E2) values, the charge radii, and the shape deformation a of the nuclear core. It is found that the reduction of the B(E2) values in C-13(Lambda) and C-14(Lambda Lambda) 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 Ne-21(Lambda) and Ne-22(Lambda Lambda). Comparison between this and other theoretical models are made, and the differences between them are illuminated.