Pairing Properties in Relativistic Mean Field Models Based on Effective Field Theory

Abstract

To study ground-state properties of open-shell nuclei one has to take into account the pairing correlations. For nuclei near the ß-stability line, where the main effect of the pairing correlations is a smearing of the Fermi surface, the BCS approximation can be used. The limitations of this simple method appear when one deals with nuclei close to the drip lines. For these nuclei the Fermi level falls near the particle continuum and it is known that the BCS model does not provide a correct description of the coupling between bound and continuum states [1]. In the non-relativistic framework this difficulty is overcome by the unified description of the mean field and the pairing correlations provided by the Hartree—Fock—Bogoliubov (HFB) theory, with Skyrme or Gogny forces. If one tries to apply the same unified treatment to the relativistic framework, several problems related with the treatment of the large momentum transfer avoid a quantitative description of the pairing correlations in nuclei within the RMF theory [2]. To overcome this problem in the relativistic Hartree-plus-Bogoliubov (RHB) calculations, the pairing part of the Gogny force [3] or a density-dependent zero range pairing force [4] have been used in the particle-particle channel together with a RMF description of the particle-hole channel.