NuclearPhysicsA35~1981)203c-214~. Q North-HoUandPublishingCo., Amsterdam Not to be reproduced by photopnnt OImicrofti without written permission from the publisher. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA A MEAN FIELD APPROACH FOR THE INTERPRETATION OF ELECTRON SCATTERING EXPERIMENTS: RESULTS AND PERSPECTIVESf J. DECHARGE, 11. GIROD, D. GOGNY and B. GRAMMATICOSft Service de Physique Neutronique et Nucleaire Centre d'Etudes de Bruyeres le ChZtel, BP 561, 92542 Hontrouge Abstract: A microscopic approach based on the mean field assumption is used for the description of nuclear structure and the interpretation of electron scattering experiments. Static results are presented for the nuclear ground states obtai- ned with the Hartree-Fock-Bogoliubov method. It is also shown that the inclu- sion of large range and dynamical correlations can substantially improve the agreement with experiment for the ground state while allowing a description of the excited states as well. 1. Introduction In the last few years the quality and quantity of data provided by electron scattering have both received a tremendous boost'). High transfer experiments com- bined with model independent analyses resulted in a most precise determination of the nuclear charge distribution down to the core of the nucleus: apart from a small central region the error bars on the experimentally determined proton density are smaller than the thicknessofthe drawing line. In the case of inelastic scattering, high q experiments allow the extraction of the transition densities from the ground state to selected low-lying excited states of the system. Magnetic electron scat- tering can also be a source of most useful information: performed on the appropria- te odd-even nuclei, it makes possible the study of the soatial distribution of es- sentially the valence nucleon'. This abundance of high quality experimental data presents the theorist with the challenge of providing an accurate interpretation. One is faced not only with the problem of calculating the various experimentally measurable quantities but al- so to choose among the existing microscopic approaches those which are sufficien- tly refined as to allow a satisfactory interpretation of the data. Furthermore, at the high transfers involved in the experimental studies, a simple non relativistic approach is often inadequate and mesonic degrees of freedom must be taken explici- tly into account. Even limiting oneself to the relativistic case, one is still fa- ced with a formidable task whenever one attempts to calculate nuclear properties using a "realistic" interaction and a more or less accurate solution of the many- body SchrBdinger equation2y3). Fortunately enough there exists a class of approxi- mations based on the nuclear mean field assumption4), which, although retaining most of the desirable features of a more fundamental theory, are suitable to cal- culations. In such approaches, and due to the restriction of the nuclear wavefunction to a class compatible with the mean-field assumption, one is led,., naturally, to the replacement of the nuclear force by an effective one. This effective interaction must account for all the complexity left out of the nuclear wavefunction. This is achieved through an adjustment of the parameters of the interaction on pertinent data, although one of the features as for example the density dependence, can be predicted on general principles. Once the effective interaction is given anda space of wave functions is speci- fied, one can calculate the energy of the nucleus and obtain through the applica- tion of a variational principle in a self-consistent manner, the ground state pro- 'Presented by B. Grammaticos. tt CRN de Strasbourg, BP 20, 67037 Strasbourg, France. 203~