Particle-number-conserving method for treating the nuclear pairing correlation

Abstract

A particle-number-conserving (PNC) method for treating the nuclear pairing correlation is presented. The difficulties encountered in the BCS method (particle-number nonconservation, spurious states, blocking effect and orthogonality, etc.) disappear in the PNC treatment. A detailed comparison between the BCS and PNC methods is made. It is found that the shape and the state density of the low-lying spectra obtained are quite different from those of the quasiparticle spectra obtained in the BCS method. Large differences between the two methods are found in the occupation probabilities in the excited states, the branching ratios for two-particle transfer reactions, etc. Blocking effects in the energy and the moment of inertia are analyzed. The residual quasiparticle interaction and the relation between the even-odd mass difference and quasiparticle energy are investigated. Pair vibration and pair rotation are investigated in the framework of the PNC formalism.