Study Of Contributions Of Dirac Sea In Quasielastic Electron Scattering From Nuclei

More than forty years of experimentation have proved that electron scattering is one of the best method for exploring atomic nuclei. The electromagnetic interaction between electrons and nucleons is very weak compared to the strength of the interaction between nucleons ,thus electron scattering is adequately treated assuming the validity of the Born approximation and one photon exchange approximation. The scattering cross-section is expressed in terms of the nuclear response functions and we can obtain lots of information of nuclear properties from the response functions .Despite the success of the nonrelativistic many-body formalism in explaining nuclear structure in terms of static two nucleon potential this approach is clearly inadequate for a full understanding of nuclei. At present the relativistic field theory has been widely used to study nuclear structure. In this paper we choose the simplest QHD model-Walecka model to describe the nuclear matter .In this model only neutral scalar meson and neutral vector meson are included. In Walecka model the coupling constants between nucleons and mesons is very strong, so it is necessary to carry out non-perturbative calculations ,one at least sumes the subseries of perturbative diagrams. For the current-current correlation function we have summed the ring diagrams(random-phase-approximation ) and for the full nucleon propagator we have summed the tadpole diagrams(considering vacuum polarization and carrying out self-consistent calculation,　called relativistic Hartree Approximation).In Walecka model, the nucleons interact with each other by exchange virtual mesons and the nucleons don't have internal structure. The divergence of FF terms coming from the Dirac electromagnetic current can be renormalized by introducing counterterms and renormalization conditions.While the FF terms coming from anomalous current are nonrenormalizable.HARUKI KURASAWA has omitted the FF terms coming from anomalous electromagnetic current. We find that the divergent integrals in the anomalous FF terms is just one of the divergent integral in the Dirac FF terms, so we can make the anomalous FF terms finite by carrying out the same subtraction just as the Dirac FF terms.From the numerical results we find that the Dirac FF terms have very obvious influence upon transverse and longitudinal nuclear response functions but the longitudinal nuclear response functions only decrease about three percent due to the anomalous FF term's contribution,and the anomalous FF terms have no obvious influence upon the transverse nuclear response functions. The numerical results indicate that the particle—antiparticle excitation is important only in the Dirac FF terms and it is not necessary to consider the contributions coming from the anomalous FF terms.In this paper we only consider the nuclear matter since there is no good renormalization methods for finite nuclei.