Pairing vibrations study with the time-dependent Hartree-Fock-Bogoliubov theory

We study pairing vibrations in ^18,20,22O and ^42,44,46Ca nuclei solving the time-dependent Hartree-Fock-Bogoliubov equation in coordinate space with spherical symmetry. We use the SLy4 Skyrme functional in the normal part of the energy density functional and a local density dependent functional in its pairing part. Pairing vibrations are excited by two-neutron transfer operators. Strength distributions are obtained using the Fourier transform of the time-dependent response of two-neutron pair-transfer observables in the linear regime. Results are in overall agreement with quasiparticle random phase approximation calculations for oxygen isotopes, though differences appear when increasing the neutron number. Both low-lying pairing modes and giant pairing vibrations (GPV) are discussed. The GPV is observed in the oxygen but not in the calcium isotopes.