Isoscalar and isovector density dependence of the pairing functional determined from global fitting

摘要

We optimize the density dependence of a local energy density functional for pairing correlations (pair-DF),ntaking into account both the isoscalar and the isovector densities. All the experimental pairing gaps in even-evennnuclei with N,Z > 8 are analyzed by performing the Hartree-Fock-Bogoliubov calculation. The new pairingnenergy density functionals give the best fit for all the pairing gaps with the rms deviation of σtot = (260–360) keV,ndepending on adopted Skyrme interactions in the particle-hole channel. It is shown that the isoscalar-densityndependence in the pair-DF can be determined almost uniquely for the several Skyrme forces by adjusting thenneutron and proton pairing gaps. An empirical relation among the parameters in the isoscalar part of pair-DF isnextracted. The uncertainty of the isovector part is also examined by calculating the pairing gaps of neutron-richnand proton-rich nuclei in a wider region of the nuclear chart. We point out also that the linear isovector-densityndependence in the pair-DF can mimic well the Coulomb effect for pairing correlations in neutron-rich nuclei.Wendiscuss finally the predictive power of the pair-DF for pairing properties around drip-line regions.