Realistic microscopic approach to deep inelastic scattering of electrons off few-nucleon systems

The contribution of the nucleonic component to deep inelastic lepton scattering off ${}_{}{}^2{}_{}{}^{}\mathrm{H}$, ${}_{}{}^3{}_{}{}^{}\mathrm{H}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ nuclei is analyzed in terms of momentum distributions and spectral functions obtained from few-body calculations which employ realistic nucleon-nucleon interactions. The nuclear structure function is evaluated within the framework of the convolution model taking relativistic effects into account by means of the flux factor. A comparison with previous calculations performed with a nonrelativistic normalization of the spectral function and using, in the case of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, an independent particle model, is presented. It is shown that short-range and tensor correlations resulting from realistic nucleon-nucleon interactions strongly increase the nucleon mean removal and kinetic energies and, consequently, enhance the calculated European Muon Collaboration effect in the direction suggested by the experimental data in the region 0.2≤x≤0.7; for x≤0.2 and x≥0.7, an appreciable discrepancy between theory and experiment still persists and the difficulties in giving an interpretation of the effect in the whole range of x, in terms of nucleonic degrees of freedom only, are pointed out. The role of ${\mathit{Q}}^2$ rescaling is analyzed; it is found that present experimental data seem to require only a small increase of the quark confinement size for a nucleon imbedded in the nuclear medium. The nuclear structure function for three-nucleon systems is calculated in the region x>1, where it is shown to be very sensitive to the correlation structure of the nucleon spectral function.