Giant halos in relativistic and nonrelativistic approaches

The phenomena of giant halo and halo of neutron-rich even-Ca isotopes are investigated and compared in the frameworks 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 the difference in shell structure. The reasons for the latter can be partly explained by the neutron 3s(1/2) orbit, causes more than 50% of the difference among the four calculations for neutron rms radii at Ca-66.