Properties of the bound nucleons

Abstract

We present recent investigations on the properties of nucleons in nuclear matter and, in particular, nucleon electromagnetic form factors in the framework of the in-medium modified Skyrme model. Medium modifications are achieved by introducing the pion-nucleus optical potential for the pion fields in nuclear environment. In order to reproduce the bulk matter properties, the parametrization of the Skyrme term in the nu- clear matter has been adjusted and the sensitivity of results to the pion-nucleus optical potential parameters are discussed. In studying nuclear matter properties one can also start from an alternative approach: we first modify nucleon properties in nuclear environment according to some general rules and considerations, and then try to reproduce the properties of the nuclear matter itself. The in-medium modified Skyrme model (6) and its recently improved version (7) are based on a such approach and allow one to perform pertinent studies in a single and many-body levels. Initially, the in-medium modified Skyrme model (6) has been proposed to study single nucleon properties in nuclear environment not only by guessing the corresponding changes in input parameters of the Lagrangian according to the density changes but also relate those changes to the existing phenomenological data, i.e. to the pion physics in nuclear matter. These studies do not take into account the direct and obvious changes of the quark core of the nucleon but take a small influence of the surrounding environment to the nucleon core via the pion profile changes. Furthermore, to be more realistic and to utilize more phenomenological information from the many-body sector, the core part of the nucleon also was modified and that medium modification has been adjusted to reproduce the binding energy of the whole system (7). While there are no explicit quark degrees of freedom and the core of the nucleon in the Skyrme model is e ectively represented by the Skyrme term in the e ective Lagrangian, core modifications are related to the change of the Skyrme parameter. In more detailed treatments Skyrme's quartic stabilizing term may be revised by explicit vector meson degrees of freedom. In the present work, we discuss the changes in the electromagnetic properties of the bound nucle- ons, based on the e ective Lagrangian discussed in Ref. (7). In this context, the electromagnetic form factors of the bound nucleons can be directly related to the existing experimental indications coming from the structure studies of the matter under extreme conditions.