Momentum-dependent mean field based upon the Dirac-Brueckner approach for nuclear matter.

A momentum-dependent mean field potential, suitable for application in the transport-model description of nucleus-nucleus collisions, is derived in a microscopic way. The derivation is based upon the Bonn meson-exchange model for the nucleon-nucleon interaction and the Dirac-Brueckner approach for nuclear matter. The properties of the microscopic mean field are examined and compared with phenomenological parametrizations which are commonly used in transport-model calculations. 1 The microscopic description of nuclear matter, finite nuclei, and nuclear reactions in terms of the realistic nucleon-nucleon (NN) interaction continues to be an interesting topic in nuclear physics. Although quantum chromodynamics (QCD) is believed to be the ultimate theory of strong interaction, the only quantitative NN potential models available up till now are based on the idea of meson exchange; a well-known example is the Bonn potential [1,2]. Special many-body theories, such as the Brueckner approach and the variational method, have been developed such that a realistic NN interaction can be applied in nuclear many-body calculations. Nuclear matter saturation has been quantitatively explained by the Dirac-Brueckner-Hartree-Fock (DBHF) approach [3–6], starting from a realistic NN interaction. Thus, this approach provides a natural starting point for the self-consistent description of nuclear matter, nuclear structure, and nuclear reactions in terms of the realistic NN interaction. The extension of the DBHF approach from nuclear matter to the structure of finite nuclei and nucleon-nucleus scattering have been attempted [7–11]. The direct solution of the DBHF equation in finite nuclei is, however, rather involved. More practically, one either parametrizes the DBHF results in nuclear matter in terms of simple Lagrangians [9–12] that can be easily applied in finite nuclei, or one performes a full Brueckner-Hartree-Fock (BHF) calculation in the finite nucleus taking the relativistic effects via the local-density approximation into account [8]. In tune with the latter approach, we present in this paper a momentum-dependent mean field single-particle potential derived from DBHF nuclear matter calculations. This mean field potential is suitable for application in the transport-model description of nucleus-nucleus collisions. Together with the in-medium NN cross sections derived in our earlier work [13], a fully self-consistent calculation of nucleus-nucleus collisions can then be performed. A self-consistent approach has been pursued in Refs. [14–17] applying the Reid soft-core potential [18] in a non-relativistic Brueckner-Hartree-Fock (BHF) calculation. The major criticism [19] of this study comes from the fact that the BHF calculation cannot even reproduce quantitatively the saturation properties of static nuclear matter [20]; the …