  The phenomena of giant halo and halo of neutron-rich even-Ca isotopes are
investigated and compared in the framework of the relativistic continuum
Hartree-Bogoliubov (RCHB) and non-relativistic Skyrme Hartree-Fock-Bogoliubov
(HFB) calculations. With two parameter sets for each of the RCHB and the Skyrme
HFB calculations, it is found that although halo phenomena exist for Ca
isotopes near neutron drip line in both calculations, the halo of the Skyrme
HFB calculations starts at a more neutron-rich nucleus than that of the RCHB
calculations, and the RCHB calculations have larger neutron root-mean-square
(rms) radii systematically in N >= 40 than those of the Skyrme HFB
calculations. The former difference comes from difference in shell structure.
The reasons for the latter can be partly explained by the neutron 3s1/2 orbit,
which causes more than 50% of the difference among the four calculations for
neutron rms radii at 66Ca.

Nuclear Theory